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1
Cohen, R. J. "Circumstellar envelopes of OH-IR sources". Symposium - International Astronomical Union 122 (1987): 229–39. http://dx.doi.org/10.1017/s0074180900156499.
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This article reviews recent radio observations of maser emission from OH, H2O and SiO molecules in the circumstellar envelopes of OH-IR sources. The different radio lines require different conditions for their excitation, and each therefore probes different regions in the circumstellar envelope. For some stars radio interferometer maps of several maser lines are now available, and a consistent picture of the envelope structure is beginning to emerge.
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Riffel, Rogemar A., Thaisa Storchi-Bergmann y Rogério Riffel. "Near-IR Integral Field Spectroscopy of the central region of NGC 5929". Proceedings of the International Astronomical Union 10, S309 (julio de 2014): 339. http://dx.doi.org/10.1017/s1743921314010321.
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AbstractWe present two-dimensional (2D) near-infrared spectra of the inner 300×300 pc2 of the Seyfert 2 galaxy NGC 5929 at a spatial resolution of ~20 pc obtained with the Gemini Near infrared Integral Field Spectrograph (NIFS). We present 2D maps for the emission line flux distributions and kinematics and report the discovery of a linear structure ~300 pc in extent and of ~50 pc in width oriented perpendicular to the radio jet, showing broadened emission-line profiles.While over most of the field the emission-line profiles have full-widths-at-half-maximum (FWHM) of ~210 km/s, at a linear structure perpendicular do the radio jet the emission-line FWHMs are twice this value, and are due to two velocity components, one blueshifted and the other redshifted relative to the systemic velocity. We attribute these velocities to an outflow from the nucleus which is launched perpendicular to the radio jet. We reported the detection of this peculiar outflow in Riffel, Storchi-Bergmann & Riffel (2014a), where more details of the analysis can be found. Since, NGC 5929 has a Type 2 nucleus, this detection implies that: (1) both ionizing radiation and relativistic particles are escaping through holes in the torus perpendicular to the radio jet; and/or (2) the torus is also outflowing, as proposed by recent models of tori as winds from the outer parts of an accretion flow; or (3) the torus is absent in NGC 5929.At other locations the gas kinematics is dominated by rotation in a disk, although some evidences of interaction of the radio jet with the emitting gas are seen as a broadening of the line profiles at the locations of the radio structures.The flux distributions for the [P ii], [Fe ii], H i and H2 emission lines show that the line emission is more extended along the PA = 60/240^, extending to up to 1.5” to both sides of the nucleus, while to the perpendicular direction (PA = -30/150^) the emission is extended to 0.7” from the nucleus. The flux distributions of all emission lines show a good correlation with radio the radio structures, with the two peak of emission associated to the soutwestern and northeastern radio knots. Some differences are observed among distinct emission lines. While the [Fe ii] and H2 emission peak at the location of the soutwestern radio structure at 0.6” from the nucleus, the H i recombination lines present the their highest fluxes at the location of the northeastern radio hotspot at 0.5” from the nucleus. Another difference is that the H2 emission is less collimated than that for other lines, being more extended perpendicularly to the radio jet. A detailed analysis of the line emission and kinematics will be presented in Riffel, Storchi-Bergmann & Riffel (2014b).
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Ferris, E. R., A. W. Blain, R. J. Assef, N. A. Hatch, A. Kimball, M. Kim, A. Sajina et al. "The black hole masses of extremely luminous radio-WISE selected galaxies". Monthly Notices of the Royal Astronomical Society 502, n.º 1 (11 de enero de 2021): 1527–48. http://dx.doi.org/10.1093/mnras/stab048.
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ABSTRACT We present near-IR photometry and spectroscopy of 30 extremely luminous radio and mid-IR-selected galaxies. With bolometric luminosities exceeding ∼1013 $\rm {L_{\odot }}$ and redshifts ranging from z = 0.880 to 2.853, we use Very Large Telescope instruments X-shooter and Infrared Spectrometer and Array Camera to investigate this unique population of galaxies. Broad multicomponent emission lines are detected in 18 galaxies and we measure the near-IR lines $\rm {H\,\rm {\beta }}$, $\rm{[O\,{\small III}]}\, \rm {\lambda }\rm {\lambda }4959,5007$, and $\rm {H\,\rm {\alpha }}$ in 6, 15, and 13 galaxies, respectively, with 10 $\rm {Ly\,\alpha }$ and 5 C iv lines additionally detected in the UVB arm. We use the broad $\rm{[O\,{\small III}]}\, \rm {\lambda }5007$ emission lines as a proxy for the bolometric active galactic nucleus luminosity, and derive lower limits to supermassive black hole masses of 107.9–109.4 M⊙ with expectations of corresponding host masses of 1010.4–1012.0 M⊙. We measure $\rm {\lambda }_{Edd}$ > 1 for eight of these sources at a 2σ significance. Near-IR photometry and SED fitting are used to compare stellar masses directly. We detect both Balmer lines in five galaxies and use these to infer a mean visual extinction of AV = 2.68 mag. Due to non-detections and uncertainties in our ${\rm H}\, \beta$ emission line measurements, we simulate a broad ${\rm H}\, \beta$ line of FWHM = 1480 $\rm {kms^{-1}}$ to estimate extinction for all sources with measured ${\rm H}\, \alpha$ emission. We then use this to infer a mean AV = 3.62 mag, demonstrating the highly obscured nature of these galaxies, with the consequence of increasing our estimates of black hole masses by a 0.5 orders of magnitude in the most extreme and obscured cases.
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di Serego Alighieri, Sperello y Andrea Cimatti. "Misdirected Quasars in Distant Radio Galaxies". Symposium - International Astronomical Union 159 (1994): 21–24. http://dx.doi.org/10.1017/s0074180900174789.
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We present the results of recent spectro–polarimetry and imaging–polarimetry of distant radio galaxies which show: (1) broad polarized permitted emission lines, (2) narrow unpolarized forbidden emission lines, (3) a flat (in fλ) polarized UV continuum and (4) an absorption feature, probably interstellar. The direction of the E vector of polarization is always perpendicular to the optical/radio axis. These observations are strong evidence that these objects harbour a quasar, which is visible only through scattering by the interstellar medium of the galaxy. The continuum polarization drops to the red of the 4000Å break, suggesting dilution by an evolved stellar population. A two-component model made of a dust scattered quasar and an evolved stellar population reproduces well the polarization and the spectral energy distribution, including the IR data.
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Down, Emily. "Modeling the Orientation of AGN". Proceedings of the International Astronomical Union 5, S267 (agosto de 2009): 107. http://dx.doi.org/10.1017/s1743921310005685.
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The orientation of nineteen 0.8< z < 2.3 radio-loud quasars was measured using two independent methods. First, Hα was observed in the near IR using ISAAC at the VLT. The complex Hα emission lines were fitted with a range of models, some including emission from a flattened, extended accretion disk following Chen & Halpern (1989). The models were compared using the Bayesian evidence, and the disk axis angles recovered. Second, models were fitted to the ~10 MHz to 20 GHz radio spectral energy distributions (SEDs) to recover the jet angles, assuming that the emission is comprised of a broken power law arising from the radio lobes plus a Doppler-boosted core.
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Maxfield, L., S. G. Djorgovski, D. Thompson, M. A. Pahre, R. R. de Carvalho, M. Vigotti y G. Grueff. "Optical and IR Properties of Radio Galaxies as a Function of their Radio Power". Symposium - International Astronomical Union 171 (1996): 414. http://dx.doi.org/10.1017/s0074180900233330.
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We compare optical and infrared photometric and spectroscopic properties of high-redshift radio galaxies from the 3CR and B3 surveys. At a given redshift and a fixed restframe frequency, the two samples differ on average by an order of magnitude in radio power, thus providing a fair baseline in radio powerfor a range of redshifts. We present new optical and IR photometry and spectrosopy for a number of B3 sources. We combine these data with the existing corresponding information on B3 and 3CR sources, in order to explore different correlations of source properties with redshift, and among themselves. B3 sources follow the same trend as 3CR's in the K band Hubble diagram, although they do seem to be slightly fainter on average at a given redshift. This trend is slightly more prominent in the Gunn r band. This suggests that some fraction of the observed light in the r and K bands is contributed by an active nucleus, which also powers the radio lobes. The B3's also tend to have lower emission line luminosities than 3CR's at any given redshift, suggesting that there may be a correlation between line luminosity and radio power. Such a correlation is clearly seen and is followed by both samples. It suggests that the UV emission lines are largely powered by the active nucleus, ostensibly a hidden quasar, which is also responsible for the radio emission. We also examine the behavior of the optical and radio PA alignments for the combined B3+3CR data set. We find that high-power and high-redshift subsamples for both B3's and 3CR's show the alignments more prominently, but we still cannot tell which of these variables dominates this effect. This work was supported in part by the NSF PYI award AST-9157412, and the Bressler Foundation.
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Perlman, Eric S., Chris L. Carilli, John T. Stocke y John Conway. "PKS 1413+135: A Very Young Radio Galaxy". Symposium - International Astronomical Union 175 (1996): 90–91. http://dx.doi.org/10.1017/s0074180900080141.
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PKS 1413+135 is an enigma: while classified as a BL Lac due to its polarized near-IR continuum (Stocke et al. 1992) and optical spectrum (Beichmann et al. 1981), it appears to lie within a spiral host (McHardy et al. 1991, Stocke et al. 1992). In addition, the AGN is highly obscured (Beichmann et al. 1981, Carilli et al. 1992, Stocke et al. 1992, Wiklind & Combes 1994, 1995). Yet there is no evidence that the absorbing gas is being heated and re-emitting the AGN radiation in the form of thermal IR or emission lines (as in, e.g., Sey 2s). This led Stocke et al. (1992) to suggest that the AGN might be background to the optical galaxy.
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Akujor, Chidi E., R. W. Porcas, A. R. Patnaik y A. Ardeberg. "Optically Quiet Quasars – Radio and Optical Investigations". Symposium - International Astronomical Union 159 (1994): 419. http://dx.doi.org/10.1017/s0074180900176041.
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The activity in the nuclei of bright galaxies could arise from a number of sources: they may contain compact variable radio sources, they may be strong IR/optical/X–ray continuum sources, or they may have strong emission lines. Usually but not always these properties go together as in radio loud quasars. However, there appears to exist a class of objects which resemble quasars in radio structure and brightness – have strong flat spectrum cores but appear fainter than would be suggested by their radio brightness – unidentified on sky surveys (Zensus & Porcas, 1985, in J. Dyson, ed, AGN). These are called ‘optically quiet quasars’ (OQQs).
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Tamura, S. y I. Kazes. "Detection of OH Maser Emission at 1667 MHz from IC 4997". Symposium - International Astronomical Union 131 (1989): 209. http://dx.doi.org/10.1017/s0074180900138203.
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We report the first detection of OH emission at 1667 MHz from a planetary nebula, IC 4997 (Figure 1). OH emission in satellite line of 1612 MHz was detected already from planetary nebulae not only Vy 2-2 (Davis and Seaquist 1979), but also two IRAS objects which were distinguished from OH/IR stars as planetary nebulae (Pottasch et al 1987). OH observations of IC 4997 have been carried out with the large radio telescope at Nançay, France. Highly resolved optical emission lines were obtained at the Okayama Astrophysical Observatory, Japan.
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Miroshnichenko, Anatoly S. "MWC 314 – A new galactic B[e] supergiant". Symposium - International Astronomical Union 162 (1994): 396–97. http://dx.doi.org/10.1017/s0074180900215489.
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We present a new study of MWC 314 = BD +14°3887 – a poorly investigated object with strong emission lines and IR excesses. Merrill (1927) payed attention to it because of the presence of hydrogen and Fe II emissions in its spectrum. Swensson (1942) also detected interstellar lines H and K CaII and 4430 Å band, Balmer emissions from Hα to H8, NaI 5890 and 5896 Å emissions and estimated its spectral type as gG2-3 or dG4-5 from the SED in continuum, and B2 from the excitation degree. Photospheric lines and spectral features of late-type stars were not observed. Allen (1973) noted that the object's SED corresponds to that of a late-type star but it might be a symbiotic system or a reddened normal star. The IRAS fluxes were obtained only at 12 and 25 μm. The object is unknown as a radio source. From this we can conclude that this system consists of, at least, a hot star surrounded by a gaseous envelope.
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Storchi-Bergmann, Thaisa, Rogemar A. Riffel, Fausto K. B. Barbosa y Cláudia Winge. "Near-IR integral field spectroscopy of the NLR of ESO428-G14: the role of the radio jet". Proceedings of the International Astronomical Union 2, S238 (agosto de 2006): 457–58. http://dx.doi.org/10.1017/s1743921307005935.
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AbstractWe present two-dimensional (2D) gas kinematics and excitation of the inner 300 pc of the Seyfert galaxy ESO428-G14 at a sampling of 14 pc2, from near-infrared spectroscopic observations at R=5900 obtained with the Integral Field Unit of the Gemini Near-Infrared Spectrograph. Blue-shifts of up to 400 km s−1 and velocity dispersions of up to 150 km s−1, are observed in association with the radio jet running from SE to NW along position angle 129°. Both X-rays emitted by the active galactic nucleus and shocks produced by the radio jet can excite the H2 and [Fe ii] emission lines. We use the 2D velocity dispersion maps we estimate upper limits of 90% to the contribution of the radio jet to the excitation of [Fe ii]λ1.257μm, and of 80% to the excitation of H2λ2.121μm in the jet region.
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Guzmán, F., M. Chatzikos, P. A. M. van Hoof, Dana S. Balser, M. Dehghanian, N. R. Badnell y G. J. Ferland. "H-, He-like recombination spectra – III. n-changing collisions in highly excited Rydberg states and their impact on the radio, IR, and optical recombination lines". Monthly Notices of the Royal Astronomical Society 486, n.º 1 (27 de marzo de 2019): 1003–18. http://dx.doi.org/10.1093/mnras/stz857.
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ABSTRACT At intermediate to high densities, electron (de-)excitation collisions are the dominant process for populating or depopulating high Rydberg states. In particular, the accurate knowledge of the energy changing (n-changing) collisional rates is determinant for predicting the radio recombination spectra of gaseous nebula. The different data sets present in the literature come either from impact parameter calculations or semi-empirical fits and the rate coefficients agree within a factor of 2. We show in this paper that these uncertainties cause errors lower than 5 per cent in the emission of radio recombination lines of most ionized plasmas of typical nebulae. However, in special circumstances where the transitions between Rydberg levels are amplified by maser effects, the errors can increase up to 20 per cent. We present simulations of the optical depth and Hnα line emission of active galactic nuclei broad-line regions and the Orion Nebula Blister to showcase our findings.
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Rathborne, J. M. y M. G. Burton. "Results from the South Pole Infra-Red EXplorer Telescope". Highlights of Astronomy 13 (2005): 937–44. http://dx.doi.org/10.1017/s153929960001769x.
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AbstractThe SPIREX telescope, located at the Amundsen-Scott South Pole Station, was a prototype system developed to exploit the excellent conditions for IR observing at the South Pole. Observations over two winter seasons achieved remarkably deep, high-resolution, wide-field images in the 3-5 μm wavelength regime. Several star forming complexes were observed, including NGC 6334, Chamaeleon I, η Chamaeleontis, the Carina Nebula, 30 Doradus, RCW 57, RCW 38, as well as the Galactic Center. Images were obtained of lines at 2.42/μm H2, 3.29/μm PAH and 4.05/μm Br α, as well as 3.5/μm L-band and 4.7 μm M-band continuum emission. These data, combined with near-IR, mid-IR, and radio continuum maps, reveal the environments of these star forming sites, as well as any protostars lying within them. The SPIREX project, its observing and reduction methods, and some sample data are summarized here.
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Constantin, Anca y Anil C. Seth. "M94 as a Unique Testbed for Black Hole Mass Estimates and AGN Activity at Low Luminosities". Advances in Astronomy 2012 (2012): 1–14. http://dx.doi.org/10.1155/2012/178060.
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We discuss the peculiar nature of the nucleus of M94 (NGC 4736) in the context of new measurements of the broadHαemission fromHST-STIS observations. We show that this component is unambiguously associated with the high-resolution X-ray, radio, and variable UV sources detected at the optical nucleus of this galaxy. These multiwavelength observations suggest that NGC 4736 is one of the least luminous broad-line (type 1) LINERs, withLbol=2.5×1040 erg s-1. This LINER galaxy has also possibly the least luminous broad-line region known (LHα=2.2×1037 erg s-1). We compare black hole mass estimates of this system to the recently measured∼7×106 M⨀dynamical black hole mass measurement. The fundamental plane andM-σ*relationship roughly agree with the measured black hole mass, while other accretion-based estimates (theM-FWHM(Hα)relation, empirical correlation of BH mass with high-ionization mid-IR emission lines, and the X-ray excess variance) provide much lower estimates (∼105 M⨀). An energy budget test shows that the AGN in this system may be deficient in ionizing radiation relative to the observed emission-line activity. This deficiency may result from source variability or the superposition of multiple sources including supernovae.
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Komossa, S. "A new probe of black holes and their environment: Luminous flares from tidally disrupted stars". Proceedings of the International Astronomical Union 8, S290 (agosto de 2012): 53–56. http://dx.doi.org/10.1017/s1743921312019199.
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AbstractThe luminous accretion flares from tidally disrupted stars represent a powerful probe of the presence of supermassive black holes (SMBHs) in otherwise non-active galaxies, of accretion physics and BH spin, of jet formation, and relativistic effects. Further, the reprocessing of the continuum radiation of the flare into IR, optical and UV emission lines provides us with multiple new diagnostics of the properties of any gaseous material in the vicinity of the SMBH and in the host galaxy itself. While first events were discovered in the course of the ROSAT all-sky survey in X-rays, the last few years have seen the detection of several more flares, including in the UV, optical and radio band and via their emission-line “echoes”. A wealth of applications will become feasible in upcoming years, once flares are detected in large numbers in current and future sky surveys.
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Harrington, Kevin C., A. Vishwas, A. Weiß, B. Magnelli, L. Grassitelli, M. Zajaček, E. F. Jiménez-Andrade et al. "The ‘Red Radio Ring’: ionized and molecular gas in a starburst/active galactic nucleus at z ∼ 2.55". Monthly Notices of the Royal Astronomical Society 488, n.º 2 (3 de julio de 2019): 1489–500. http://dx.doi.org/10.1093/mnras/stz1740.
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ABSTRACT We report the detection of the far-infrared (FIR) fine-structure line of singly ionized nitrogen, [N ii] 205 $\mu$m , within the peak epoch of galaxy assembly, from a strongly lensed galaxy, hereafter ‘The Red Radio Ring’; the RRR, at z = 2.55. We combine new observations of the ground-state and mid-J transitions of CO (Jup = 1, 5, 8), and the FIR spectral energy distribution (SED), to explore the multiphase interstellar medium (ISM) properties of the RRR. All line profiles suggest that the H ii regions, traced by [N ii] 205 $\mu$m , and the (diffuse and dense) molecular gas, traced by CO, are cospatial when averaged over kpc-sized regions. Using its mid-IR-to-millimetre (mm) SED, we derive a non-negligible dust attenuation of the [N ii] 205 $\mu$m line emission. Assuming a uniform dust screen approximation results a mean molecular gas column density >1024 cm−2, with a molecular gas-to-dust mass ratio of 100. It is clear that dust attenuation corrections should be accounted for when studying FIR fine-structure lines in such systems. The attenuation corrected ratio of $L_{\rm N\,{\small II}205} / L_{\rm IR(8\!-\!1000\, \mu m)} = 2.7 \times 10^{-4}$ is consistent with the dispersion of local and z > 4 SFGs. We find that the lower limit, [N ii] 205 $\mu$m -based star formation rate (SFR) is less than the IR-derived SFR by a factor of 4. Finally, the dust SED, CO line SED, and $L_{\rm N\,{\small II}205}$ line-to-IR luminosity ratio of the RRR is consistent with a starburst-powered ISM.
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Mickaelian, A. M., L. A. Sargsyan, L. K. Erastova, S. K. Balayan, K. S. Gigoyan, L. R. Hovhannisyan, R. Nesci et al. "The Digitized First Byurakan Survey - DFBS". Symposium - International Astronomical Union 216 (2005): 230–38. http://dx.doi.org/10.1017/s0074180900196676.
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The First Byurakan Survey (FBS) is the largest spectral survey in the Northern sky. One can select objects by color, broad absorption and emission lines, and SED; classify and investigate them. The digitization of the FBS is aimed at making a DFBS database available for the astronomical community. Besides scanning, we are creating plate solutions, extraction software, wavelength and flux calibration, templates for different types of objects, numerical classification, a catalog of objects, a database of spectra, a user interface and a DFBS web page. New research projects based on the DFBS are possible, including a search for new QSOs and other AGN, a continuation of the second part of FBS, and identifications of radio, IR and X-ray sources. The DFBS database will be available at the end of 2004.
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Lamers, Henny J. G. L. M. "Mass loss from Luminous Blue Variables". International Astronomical Union Colloquium 113 (1989): 135–48. http://dx.doi.org/10.1017/s0252921100004395.
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Luminous Blue Variables (LBV’s) are losing mass at a rate which is higher than in normal stars of the same luminosity. This high mass loss is evident from the occurrence of P Cygni profiles in the visual spectrum, the large numbers of UV lines which are Doppler shifted or show P Cygni profiles and the large IR excess or radio free-free emission. Mass loss from LBV’s is strongly variable on a wide range of timescales from months to centuries and possibly even millenia. During these variations the mass loss may vary from values as low as 10-6to 10-5M⊙/yr, when the star is quiet, to outbursts of the type observed in P Cygni in AD 1600 and n Car in 1837 (for reviews see Davidson, 1987; Lamers, 1986, 1987).
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Mickaelian, Areg M. y Gohar S. Harutyunyan. "Study of the Byurakan-IRAS galaxy sample". Proceedings of the International Astronomical Union 8, S292 (agosto de 2012): 159. http://dx.doi.org/10.1017/s1743921313000896.
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AbstractThe Byurakan-IRAS Galaxy (BIG) sample (Mickaelian 1995) is the result of optical identifications of IRAS PSC sources at high-galactic latitudes using the First Byurakan Survey (FBS) low-dispersion spectra (Markarian et al. 1989). Among the 1577 objects 1178 galaxies have been identified. Most are dusty spiral galaxies and there are a number of ULIRGs among these objects. Our spectroscopic observations carried out with three telescopes (Byurakan Astrophysical Observatory 2.6m, Russian Special Astrophysical Observatory 6m and Observatoire de Haute Provence 1.93m) (Mickaelian & Sargsyan 2010) for 172 galaxies, as well as the SDSS DR8 spectra for 83 galaxies make up the list of 255 spectroscopically studied BIG objects. The classification to activity types for narrow-line emission galaxies has been carried out using the diagnostic diagrams by Veilleux & Osterbrock (1987). All possible physical characteristics have been measured and/or calculated, including radial velocities and distances, angular and physical sizes, absolute magnitudes and luminosities (both optical and IR). IR luminosities and star-formation rates have been calculated from the IR fluxes (Duc et al. 1997).Among the 172 observed galaxies, 102 starburst (HII) ones, 29 AGN (Sy or LINER), and 19 galaxies with composite spectrum have been revealed; spectra of 12 galaxies show emission features but without a possibility for more accurate classification, 9 galaxies are presented as galaxies where the star formation rate does not exceed normal one, and 1 galaxy is an absorption galaxy. Among the 83 objects having SDSS spectra, there are 55 HIIs, 8 Seyferts, 2 LINERs, 4 other AGN (without accurate classification), 6 composite spectrum objects and 8 other emission-line galaxies. In our spectroscopic sample we have 43 (17%) AGN, 25 (10%) composite spectrum objects, 157 (62%) starbursts, 29 emission-line galaxies without a definite type, and 1 absorption-line galaxy. There are 3 Ultra-Luminous InfraRed Galaxies (ULIRG).Various multiwavelength (MW) data have been retrieved for the full sample of 1178 objects from recent catalogs from X-ray to radio (ROSAT, GALEX, APM, MAPS, USNO, GSC, SDSS, 2MASS, WISE, IRAS, AKARI, NVSS, FIRST, etc.) to make a complete study of these galaxies possible. MW SEDs have been built, which have been matched to their optical classifications. Star-formation rates have been calculated to compare to their other physical characteristics, such as morphology, activity types, UV, optical, IR and radio luminosities, etc.
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Mickaelian, Areg M. "Digitization of the FBS: Its Future Use and Expected Results". International Astronomical Union Colloquium 184 (2002): 399–408. http://dx.doi.org/10.1017/s0252921100031134.
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Abstract The First Byurakan Survey (FBS) is the largest spectral survey in the Northern sky. Its plates contain low-dispersion spectra for some 20,000,000 objects. The FBS spectra allow selection of objects by their color, broad emission or absorption lines, or SED; to discover, classify and investigate them. The FBS was conducted originally to search for UVX galaxies (1500 Markarian galaxies were discovered). Selection of blue stellar objects, red stars, and identification of IRAS sources have also been done by means of the FBS spectra. All these projects have been carried out by visual inspection of the plates. Digitization will give new possibilities to search for many new objects: new bright QSOs (m<18m), new Markarian (UVX) galaxies, BCDGs, optical counterparts of IR, radio, X-ray and other sources, late-type stars, planetary nebulae, emission-line stars, and white dwarfs; and to study star clusters and clusters of galaxies. The digitized FBS will be available via the Internet and on CDs. Software and an appropriate interface for working with the data will be provided.
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Kauffmann, Guinevere y Claudia Maraston. "Emission-line properties of the most luminous AGNs in massive galaxies at intermediate redshifts". Monthly Notices of the Royal Astronomical Society 489, n.º 2 (23 de agosto de 2019): 1973–85. http://dx.doi.org/10.1093/mnras/stz2271.
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ABSTRACT We have analysed the emission-line properties of 6019 Type II active galactic nuclei (AGNs) at redshifts in the range 0.4–0.8 with [O iii] luminosities greater than $3 \times 10^8 \, \mathrm{L}_{\odot }$, characteristic of the Type II quasars first identified in population studies by Zakamska et al. The AGNs are drawn from the CMASS sample of galaxies with stellar masses greater than $10^{11} \, \mathrm{M}_{\odot }$ that were studied as part of the Baryon Oscillation Spectroscopic Survey (BOSS) and comprise 0.5 per cent of the total population of these galaxies. Individual spectra have low S/N, so the analysis is carried out on stacked spectra in bins of [O iii] luminosity and estimated stellar age. The emission line ratios of the stacks are well fit with simple uniform-density photoionization models with metallicities between solar and twice solar. In the stacks, a number of emission lines are found to have distinct broad components requiring a double Gaussian rather than a single Gaussian fit, indicative of outflowing ionized gas. These are: [O iii] λ4959, [O iii] λ5007, [O ii] λ3727,3729, and H αλ6563. Higher ionization lines such as [Ne iii] λ3869 and [Ne v] λ3345 are detected in the stacks, but are well fit by single Gaussians. The broad components typically contain a third of the total line flux and have widths of 600 km s−1 for the oxygen lines and 900 km s−1 for H α. The fraction of the flux in the broad component and its width are independent of [O iii] luminosity, stellar age, radio, and mid-IR luminosity. The stellar mass of the galaxy is the only parameter we could identify that influences the width of the broad line component.
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Taniguchi, Kotomi, Adele Plunkett, Eric Herbst, Kazuhito Dobashi, Tomomi Shimoikura, Fumitaka Nakamura y Masao Saito. "Investigation of chemical differentiation among the NGC 2264 cluster-forming clumps". Monthly Notices of the Royal Astronomical Society 493, n.º 2 (10 de enero de 2020): 2395–409. http://dx.doi.org/10.1093/mnras/staa012.
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ABSTRACT We have carried out mapping observations of molecular emission lines of HC3N and CH3OH toward two massive cluster-forming clumps, NGC 2264-C and NGC 2264-D, using the Nobeyama 45-m radio telescope. We derive an I(HC3N)/I(CH3OH) integrated intensity ratio map, showing a higher value at clumps including 2MASS (Two Micron All Sky Survey) point sources at the northern part of NGC 2264-D. Possible interpretations of the I(HC3N)/I(CH3OH) ratio are discussed. We have also observed molecular emission lines from CCS and N2H+ toward five positions in each clump. We investigate the N(N2H+)/N(CCS) and N(N2H+)/N(HC3N) column density ratios among the ten positions in order to test whether they can be used as chemical evolutionary indicators in these clumps. The N(N2H+)/N(CCS) ratio shows a very high value toward a bright embedded IR source (IRS1), whereas the N(N2H+)/N(HC3N) ratio at IRS1 is comparable with those at the other positions. These results suggest that ultraviolet radiation affects the chemistry around IRS1. We find that there are positive correlations between these column density ratios and the excitation temperatures of N2H+, which implies the chemical evolution of clumps. These chemical evolutionary indicators likely reflect the combination of evolution along the filamentary structure and evolution of each clump.
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Calabrò, A., E. Daddi, A. Puglisi, E. Oliva, R. Gobat, P. Cassata, R. Amorín et al. "Deciphering an evolutionary sequence of merger stages in infrared-luminous starburst galaxies atz∼ 0.7". Astronomy & Astrophysics 623 (marzo de 2019): A64. http://dx.doi.org/10.1051/0004-6361/201834522.
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Based on optical and near-IRMagellanFIRE spectra of 25 starburst galaxies at 0.5 < z < 0.9, a recent publication showed that their attenuation properties can be explained by a single-parameter sequence of total obscurations ranging fromAV = 2 toAV = 30 toward the starburst core centers in a mixed stars and dust configuration. We investigate here the origin of this sequence for the same sample. We show that total attenuations anticorrelate with the starburst sizes in radio (3 GHz) with a significance larger than 5σand a scatter of 0.26 dex. More obscured and compact starbursts also show enhanced N2 (=[NII]/Hα) ratios and larger line velocity widths that we attribute to an increasing shock contribution toward later merger phases, driven by deeper gravitational potential wells at the coalescence. Additionally, the attenuation is also linked to the equivalent width (EW) of hydrogen recombination lines, which is sensitive to the luminosity weighted age of the relatively unobscured stellar populations. Overall, the correlations amongAV, tot, radio size, line width, N2 and EW of Balmer and Paschen lines converge toward suggesting an evolutionary sequence of merger stages: all of these quantities are likely to be good time-tracers of the merger phenomenon, and their large spanned range appears to be characteristic of the different merger phases. Half of our sample at higher obscurations have radio sizes approximately 3 times smaller than early type galaxies at the same redshift, suggesting that, in analogy with local ultraluminous infrared galaxies (ULIRGs), these cores cannot be directly forming elliptical galaxies. Finally, we detect mid-IR AGN torus for half of our sample and additional X-ray emission for 6 starbursts; intriguingly, the latter have systematically more compact sizes, suggestive of emerging AGNs toward later merger stages, possibly precursors of a later QSO phase.
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Nemmen, Rodrigo S., Thaisa Storchi-Bergmann, Michael Eracleous y Feng Yuan. "Advection-Dominated Accretion, Jets, and the Spectral Energy Distribution of LINERs". Proceedings of the International Astronomical Union 5, S267 (agosto de 2009): 313–18. http://dx.doi.org/10.1017/s1743921310006538.
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AbstractLow-luminosity active galactic nuclei (LLAGNs) represent the bulk of the AGN population in the present-day universe and they trace low-level accreting supermassive black holes. The observational properties of LLAGNs suggest that their central engines are intrinsically different from those of more luminous AGNs. It has been suggested that accretion in LLAGNs occurs via an advection-dominated accretion flow (ADAF) associated with strong jets. In order to probe the accretion physics in LLAGNs as a class, we model the multiwavelength spectral energy distributions (SEDs) of 24 LINERs (taken from a recent compilation by Eracleous et al.) with a coupled accretion-jet model. The accretion flow is modeled as an inner ADAF outside of which there is a truncated standard thin disk. These SEDs include radio, near-IR to near-UV HST data, and Chandra X-ray data. We find that the radio emission is severely underpredicted by ADAF models but can be explained by the relativistic jet. The origin of the X-ray radiation in most sources can be explained by three distinct scenarios: the X-rays can be dominated by emission from the ADAF, the jet, or from both components contributing at similar levels. From the model fits, we estimate important parameters of the central engine of LINERs, such as the mass accretion rate — relevant for studies of the feeding of AGNs — and the mass-loss rate in the jet and the jet power — relevant for studies of the kinetic feedback from jets.
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J Willis, Allan. "Observations of Wolf-Rayet Mass Loss". Symposium - International Astronomical Union 143 (1991): 265–80. http://dx.doi.org/10.1017/s0074180900045320.
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Current knowledge of the stellar winds and mass loss rates for WR stars is reviewed. Recent IR spectroscopy and reassessments of UV resonance line P Cygni profiles have led to revisions of terminal velocities, with v∞ ≃ 0.75 × previous estimates. Radio and IR (10μm) free-free emission for well-established thermal sources, coupled with recent considerations of the wind ionisation balance and chemistry, leads to WR mass loss rates lying in the range 10-5 − 10-4 M⊙ yr–1. This scale is confirmed by independent analyses of optical polarisation modulation in WR+O binaries. No significant differences are apparent between the mean mass loss rates of: (a) single and binary WR stars; (b) WN and WC stars, and (c) the WN and WC subclasses. The overall mean WR mass loss rate is ~ 5 × 10-5 M⊙ yr–1. Although WR radiative luminosities are uncertain, there may be a rough scaling of MWR with L∗, with a spread of up to an order of magnitude at a given L∗. WR winds have the highest momenta of the hot luminous stars, with values of M v∞ c/L∗ in the range 1-30 (WN7,8 and WC9 stars may lie near the lower bound). An additional mechanism to radiation pressure may be required to initiate the high WR mass loss, although thereafter the winds may be radiatively accelerated. Intrinsic variability in optical light, polarisation and emission lines, and in UV P Cygni profiles, indicate significant instability in the WR winds. For extragalactic WR stars in the Local Group, optical line strengths and widths do not suggest substantial differences in wind velocities and mass loss rates of subtypes compared to galactic counterparts.
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Harutyunyan, Gohar S. y Areg M. Mickaelian. "Analysis and Statistics of the Spectroscopic Sample of Byurakan-IRAS Galaxies". Proceedings of the International Astronomical Union 9, S304 (octubre de 2013): 68–69. http://dx.doi.org/10.1017/s1743921314003354.
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AbstractA summary and general analysis of optical spectroscopic data for 255 Byurakan-IRAS Galaxies (BIG) obtained with BAO 2.6m, SAO 6m, OHP 1.93m telescopes, as well as SDSS DR7, DR8, and DR9 is given. The BIG sample is the result of optical identifications of IRAS PSC sources at high-galactic latitudes using the First Byurakan Survey (FBS) low-dispersion spectra. Among the 1178 objects most are spiral galaxies and there is a number of ULIRGs. All but one have emission lines; we have discovered 68 AGN and composite spectrum objects among them and the others are mostly Starburst Galaxies (SB). All possible physical characteristics have been measured and/or calculated, including physical sizes and optical and IR/FIR luminosities. The masses have been estimated based on mass-luminosity relations for spiral galaxies. As it appears, most of these objects are giant massive galaxies. Various multiwavelength (MW) data have been retrieved from recent catalogues from X-ray to radio and MW SEDs have been built, which have been matched to their optical classifications. Luminosity evolution of these objects has been studies.
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Starrfield, S. "Multi-wavelength Observations of Novae in Outburst". International Astronomical Union Colloquium 122 (1990): 127–37. http://dx.doi.org/10.1017/s0252921100068457.
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A nova outburst is the second most violent explosion that can occur in a galaxy. While less violent than a supernova explosion, novae are considerably more frequent. More than 250 have been observed in the last century and there were more than a dozen novae being observed in outburst when this review was written. Over the past few years they have been studied at wavelengths ranging from the radio to the X-ray and these data have provided exciting new information about the nova outburst. For example, IUE studies have shown that there are two classes of novae; those that occur on carbon-oxygen white dwarfs and those that occur on oxygen-neon-magnesium white dwarfs. EXOSAT observations have shown that an intense X-ray emitting source exists in the system for years after the initial outburst has been discovered and radio studies have found that some novae are ejecting material in jets. IR studies have found high excitation coronal lines, dust formation, and have provided accurate distances. Optical studies have provided determinations of densities and temperatures in the ejecta and have discovered a class of novae that occur on strongly magnetized white dwarfs. There have been predictions but no detections of γ-ray emission. Finally, novae are time dependant and simultaneous or contemporaneous observations are required in order to learn as much as possible about the characteristics of the outburst.
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Štefl, Stanislav. "Disks of Classical Be Stars". International Astronomical Union Colloquium 169 (1999): 24–31. http://dx.doi.org/10.1017/s0252921100071724.
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AbstractObservational methods used in investigation of circumstellar disks of Be stars significantly changed during the last decade. While mostly the studies of line profiles in the optical and near-IR region were used in the 70th and 80th, the present progress is done also thanks to interferometric and polarimetric observations. These techniques enable to determine the geometrical parameters of the circumstellar disks directly for the first time. They are flattened and axially symmetric. Their H α emission region extends typically up to several tens of stellar radii. Systematic long-term spectroscopic monitoring helped to define and partly interpret the line-profile variability of emission lines on different time-scales. Variations on a time-scale of hours may appear after the matter is ejected during the outburst. The V/R variations with periods of the order of 10 years reflect the global disk oscillations.
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Perrotta, S., F. Hamann, N. L. Zakamska, R. M. Alexandroff, D. Rupke y D. Wylezalek. "ERQs are the BOSS of quasar samples: the highest velocity [O iii] quasar outflows". Monthly Notices of the Royal Astronomical Society 488, n.º 3 (25 de julio de 2019): 4126–48. http://dx.doi.org/10.1093/mnras/stz1993.
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ABSTRACT We investigate extremely red quasars (ERQs), a remarkable population of heavily reddened quasars at redshift z ∼ 2−3 that might be caught during a short-lived ‘blow-out’ phase of quasar/galaxy evolution. We perform a near-IR observational campaign using Keck/NIRSPEC, VLT/X-shooter, and Gemini/GNIRS to measure rest-frame optical spectra of 28 ERQs with median infrared luminosity 〈log L(erg s−1)〉 ∼ 46.2. They exhibit the broadest and most blueshifted [O iii] λ4959,5007 emission lines ever reported, with widths (w90) ranging between 2053 and 7227 km s−1, and maximum outflow speeds (v98) up to 6702 km s−1. ERQs on average have [O iii] outflows velocities about three times larger than those of luminosity-matched blue quasar samples. This discrepancy can be explained by a strong correlation between [O iii] kinematics and i–W3 colour, and not by radio loudness, or higher Eddington ratios. We estimate for these objects that at least 3–5 per cent of their bolometric luminosity is being converted into the kinetic power of the observed wind. Our results reveal that ERQs have the potential to strongly affect the evolution of host galaxies.
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Cuadrado, S., P. Salas, J. R. Goicoechea, J. Cernicharo, A. G. G. M. Tielens y A. Báez-Rubio. "Direct estimation of electron density in the Orion Bar PDR from mm-wave carbon recombination lines". Astronomy & Astrophysics 625 (mayo de 2019): L3. http://dx.doi.org/10.1051/0004-6361/201935556.
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Context. A significant fraction of the molecular gas in star-forming regions is irradiated by stellar UV photons. In these environments, the electron density (ne) plays a critical role in the gas dynamics, chemistry, and collisional excitation of certain molecules. Aims. We determine ne in the prototypical strongly irradiated photodissociation region (PDR), the Orion Bar, from the detection of new millimeter-wave carbon recombination lines (mmCRLs) and existing far-IR [13C II] hyperfine line observations. Methods. We detect 12 mmCRLs (including α, β, and γ transitions) observed with the IRAM 30 m telescope, at ∼25″ angular resolution, toward the H/H2 dissociation front (DF) of the Bar. We also present a mmCRL emission cut across the PDR. Results. These lines trace the C+/C/CO gas transition layer. As the much lower frequency carbon radio recombination lines, mmCRLs arise from neutral PDR gas and not from ionized gas in the adjacent H II region. This is readily seen from their narrow line profiles (Δv = 2.6 ± 0.4 km s−1) and line peak velocities (vLSR = +10.7 ± 0.2 km s−1). Optically thin [13C II] hyperfine lines and molecular lines – emitted close to the DF by trace species such as reactive ions CO+ and HOC+ – show the same line profiles. We use non-LTE excitation models of [13C II] and mmCRLs and derive ne = 60–100 cm−3 and Te = 500–600 K toward the DF. Conclusions. The inferred electron densities are high, up to an order of magnitude higher than previously thought. They provide a lower limit to the gas thermal pressure at the PDR edge without using molecular tracers. We obtain Pth ≥ (2−4) × 108 cm−3 K assuming that the electron abundance is equal to or lower than the gas-phase elemental abundance of carbon. Such elevated thermal pressures leave little room for magnetic pressure support and agree with a scenario in which the PDR photoevaporates.
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Tapia, Mauricio, Paolo Persi, Miguel Roth y Davide Elia. "An infrared study of the high-mass, multistage star-forming region IRAS 12272−6240". Monthly Notices of the Royal Astronomical Society 496, n.º 3 (20 de junio de 2020): 3358–70. http://dx.doi.org/10.1093/mnras/staa1772.
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ABSTRACT IRAS 12272−6240 is a complex star-forming region with a compact massive dense clump (DC) and several associated masers, located at a well-determined distance of d = 9.3 kpc from the Sun. For this study, we obtained sub-arcsec broad- and narrow-band near-infrared (near-IR) imaging and low-resolution spectroscopy with the Baade/Magellan telescope and its camera PANIC. Mosaics of size 2 × 2 arcmin2 in the JHKs bands and with narrow-band filters centred in the 2.12 μm H2 and 2.17 μm Br γ lines were analysed in combination with Hi-GAL/Herschel and archive IRAC/Spitzer and WISE observations. We found that the compact DC houses two Class I young stellar objects (YSOs) that probably form a 21000 -au-wide binary system. Its combined 1–1200 μm spectral energy distribution is consistent with an O9V central star with a $10^{-2} \, \mathrm{M}_\odot$ disc and a $1.3 \times 10^4 \, \mathrm{M}_\odot$ dust envelope. Its total luminosity is $8.5 \times 10^4 \, \mathrm{L}_\odot$. A series of shocked H2 emission knots are found in its close vicinity, confirming the presence of outflows. IRAS 12272−6240 is at the centre of an embedded cluster with a mean age of 1 Myr and 2.6 pc in size that contains more than 150 stars. At its nucleus, we found a more compact and considerably younger subcluster containing the YSOs. We also identified and classified the O-type central stars of two dusty radio/IR H ii regions flanking the protostars. Our results confirm that these elements form a single giant young complex where massive star formation processes started some 1 Myr ago and are still active.
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D’Eugenio, C., E. Daddi, R. Gobat, V. Strazzullo, P. Lustig, I. Delvecchio, S. Jin, A. Cimatti y M. Onodera. "HST grism spectroscopy of z ∼ 3 massive quiescent galaxies". Astronomy & Astrophysics 653 (septiembre de 2021): A32. http://dx.doi.org/10.1051/0004-6361/202040067.
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Tracing the emergence of the massive quiescent galaxy (QG) population requires the build-up of reliable quenched samples by distinguishing these systems from red, dusty star-forming sources. We present Hubble Space Telescope WFC3/G141 grism spectra of ten quiescent galaxy candidates selected at 2.5 < z < 3.5 in the COSMOS field. Spectroscopic confirmation for the whole sample is obtained within one to three orbits through the detection of strong spectral breaks and Balmer absorption lines. When their spectra are combined with optical to near-infrared photometry, star-forming solutions are formally rejected for the entire sample. Broad spectral indices are consistent with the presence of young A-type stars, which indicates that the last major episode of star formation has taken place no earlier than ∼300–800 Myr prior to observation. This confirms clues from their post-starburst UVJ colors. Marginalising over three different slopes of the dust attenuation curve, we obtain young mass-weighted ages and an average peak star formation rate (SFR) of ∼103 M⊙ yr−1 at zformation ∼ 3.5. Although mid- and far-IR data are too shallow to determine the obscured SFR on a galaxy-by-galaxy basis, the mean stacked emission from 3 GHz data constrains the level of residual-obscured SFR to be globally below 50 M⊙ yr−1, three times below the scatter of the coeval main sequence. Alternatively, the very same radio detection suggests a widespread radio-mode feedback by active galactic nuclei (AGN) four times stronger than in z ∼ 1.8 massive QGs. This is accompanied by a 30% fraction of X-ray luminous AGN with a black hole accretion rate per unit SFR enhanced by a factor of ∼30 with respect to similarly massive QGs at lower redshift. The average compact, high Sérsic index morphologies of the galaxies in this sample, coupled with their young mass-weighted ages, suggest that the mechanisms responsible for the development of a spheroidal component might be concomitant with (or preceding) those causing their quenching.
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Killeen, N. E. B., K. Y. Lo, R. J. Sault y R. M. Crutcher. "OH Zeeman Determination of the Magnetic Field at the Galactic Centre". Symposium - International Astronomical Union 140 (1990): 382. http://dx.doi.org/10.1017/s0074180900190588.
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Mid and far IR measurements of polarized dust continuum emission from within the central 5 pc of the Galaxy have been cited as evidence for magnetic alignment of dust grains. Indirect arguments have been used to infer a B-field strength of ~ 10 mG. The presence of such high B-field would play a significant role in the hydrodynamics of the ionized and neutral gas within the region. To obtain a direct measurement of the line-of-sight B-field strength, we conducted VLA observations to try and detect the Zeeman splitting in the 1667 MHz OH absorption line against the SgrA radio source. We observed with A/B configuration, 256 1.1 km s−1 channels, and 3 arcsec resolution. In addition, both left and right circular polarizations were acquired simultaneously. We used the maximum likelihood statistical analysis technique for low signal-to-noise ratio Zeeman data discussed by Sault, Killeen, Loushin, and Zmuidzinas (1989). Analysis of the resulting absorption line spectra is complicated by the many foreground clouds. Excluding the foreground clouds by judicious selection of spectral windows, the strongest absorption by the molecular material closest (in projection) to SgrA∗ is in what Güsten et al. (1987) refer to as the redshifted cloud (it does not appear to be partaking in the general rotation of the circum-nuclear disk but is thought to be in the local vicinity of SgrA∗). Preliminary analysis reveals no detections, and 3-σ upper limits to the line-of-sight magnetic field throughout the red-shifted cloud of approximately 4 mG. By careful simulation of the lines (Gaussians are quite good approximations to these broad [40 km s−1] lines) in select spatial regions of the redshifted cloud, we find that a line-of-sight field as strong as 10 mG should be clearly detectable at about the 10-σ level if it is present. Our data do not show fields at this level.
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Jackson, Neal y I. W. A. Browne. "Quasar emission lines, radio structures and radio unification". Monthly Notices of the Royal Astronomical Society 429, n.º 2 (22 de diciembre de 2012): 1781–90. http://dx.doi.org/10.1093/mnras/sts468.
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Tabatabaei, F. S., R. Beck y E. Berkhuijsen. "The radio-infrared correlation in galaxies". Proceedings of the International Astronomical Union 5, H15 (noviembre de 2009): 417. http://dx.doi.org/10.1017/s1743921310010057.
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The radio–infrared correlation holds within galaxies down to scales of about 50 pc (Hughes et al. 2006). It was explained as a direct and linear relationship between star formation and IR emission. However, one fact making the IR-star formation linkage less obvious is that the IR emission consists of at least two emission components, cold dust and warm dust. The cold dust emission may not be directly linked to the young stellar population. Furthermore, understanding the origin of the radio–IR correlation requires to discriminate between the two main components of the radio continuum emission, free-free and synchrotron emission. Although cosmic ray electrons originates also from the star forming regions (supernovae remnants; final episodes of massive stars), the synchrotron–IR correlation may not be as tight as thermal–IR correlation locally, as a result of convection and diffusion of the cosmic ray electrons from their place of birth. The magnetic field distribution may further modify the correlation.
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Stasińska, Grażyna, Natalia Vale Asari y Dorota Kozieł-Wierzbowska. "Radio galaxies with and without emission lines". Proceedings of the International Astronomical Union 15, S359 (marzo de 2020): 396–401. http://dx.doi.org/10.1017/s1743921320001866.
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AbstractUsing the recent ROGUE I catalogue of galaxies with radio cores (Kozie_l-Wierzbowska et al. 2020) and after selecting the objects which are truly radio active galactic nuclei, AGNs, (which more than doubles the samples available so far), we perform a thorough comparison of the properties of radio galaxies with and without optical emission lines (galaxies where the equivalent width of Hα is smaller than 3Å are placed in the last category). We do not find any strong dichotomy between the two classes as regards the radio luminosities or black hole masses. The same is true when using the common classification into high- and low-excitation radio galaxies (HERGs and LERGs respectively).
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Koekemoer, A. M. y G. V. Bicknell. "Shock Excitation of Emission Lines in Radio Galaxies". Symposium - International Astronomical Union 175 (1996): 473–74. http://dx.doi.org/10.1017/s0074180900081535.
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We present evidence for the viability of “auto-ionizing” shocks as the dominant ionization mechanism in extended emission-line regions (EELRs) in two radio galaxies, PKS 0349–27 and PKS 2356–61. The application of this model, rather than the nuclear photoionization hypothesis of unified schemes (Barthel 1989), is motivated by observed EELR properties: large line-of-sight velocity widths (up to δv ≃ 500 km s–1 for nearby objects and ≳ 1000kms–1 at higher z); kinematics/excitation relationships (Baum et al. 1992); the EELR/radio axis alignment (Chambers et al. 1987, McCarthy et al. 1987); and the correspondence between the brighter EELR and the shorter radio lobe (McCarthy et al. 1991), suggestive of jet/gas interactions. We show that the flux, excitation and kinematics across the gas is self-consistently accounted for in terms of shocks as a single physical mechanism, requiring fewer unknown parameters than nuclear photoionization.
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Kijak, Jaroslaw y Janusz A. Gil. "Pulsar radio beams and emission altitudes". International Astronomical Union Colloquium 160 (1996): 287–88. http://dx.doi.org/10.1017/s0252921100041737.
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We verify the relationship proposed by Kijak and Gil (1996) for the pulsar radio emission altitudes(see also Eq.3 in Gil & Krawczyk, 1996), using the pulse-profile Effelsberg raw data at 1.41 GHz. We measured profile pulse-widths at the lowest intensity level corresponding to 0.01% of the maximum intensity (Fig. 1b), using the polarlog-scale technique (Hankins and Fowler, 1986). We calculated opening angles (Fig. 1a) and emission altitudes (Fig. 1c) assuming that:i) pulsar radiation is narrow-band with radius-to-frequency mapping operating in the emission region,ii) pulsar emission is beamed tangentially to the dipolar magnetic field lines,iii) the extreme profile wings originate near or at the last open field lines.
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Kewley, Lisa J., David C. Nicholls y Ralph S. Sutherland. "Understanding Galaxy Evolution Through Emission Lines". Annual Review of Astronomy and Astrophysics 57, n.º 1 (18 de agosto de 2019): 511–70. http://dx.doi.org/10.1146/annurev-astro-081817-051832.
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We review the use of emission lines for understanding galaxy evolution, focusing on excitation source, metallicity, ionization parameter, ISM pressure, and electron density. We discuss the physics, benefits, and caveats of emission line diagnostics, including the effects of theoretical model uncertainties, diffuse ionized gas, and sample selection bias. In anticipation of upcoming telescope facilities, we provide new self-consistent emission line diagnostic calibrations for complete spectral coverage from the UV to the IR. These diagnostics can be used in concert to understand how fundamental galaxy properties have changed across cosmic time. We conclude the following: ▪ The UV, optical, and IR contain complementary diagnostics that can probe the conditions within different nebular ionization zones. ▪ Accounting for complex density gradients and temperature profiles is critical for reliably estimating the fundamental properties of Hii regions and galaxies. ▪ Diffuse ionized gas can raise metallicity estimates, flatten metallicity gradients, and introduce scatter in ionization parameter measurements. ▪ New 3D emission line diagnostics successfully separate the contributions from star formation, AGN, and shocks using integral field spectroscopy. We summarize with a discussion of the challenges and major opportunities for emission line diagnostics in the coming years.
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Wittkowski, Markus, David A. Boboltz, Malcolm D. Gray, Elizabeth M. L. Humphreys, Iva Karovicova y Michael Scholz. "Radio and IR interferometry of SiO maser stars". Proceedings of the International Astronomical Union 8, S287 (enero de 2012): 209–16. http://dx.doi.org/10.1017/s1743921312006989.
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AbstractRadio and infrared interferometry of SiO maser stars provide complementary information on the atmosphere and circumstellar environment at comparable spatial resolution. Here, we present the latest results on the atmospheric structure and the dust condensation region of AGB stars based on our recent infrared spectro-interferometric observations, which represent the environment of SiO masers. We discuss, as an example, new results from simultaneous VLTI and VLBA observations of the Mira variable AGB star R Cnc, including VLTI near- and mid-infrared interferometry, as well as VLBA observations of the SiO maser emission toward this source. We present preliminary results from a monitoring campaign of high-frequency SiO maser emission toward evolved stars obtained with the APEX telescope, which also serves as a precursor of ALMA images of the SiO emitting region. We speculate that large-scale long-period chaotic motion in the extended molecular atmosphere may be the physical reason for observed deviations from point symmetry of atmospheric molecular layers, and for the observed erratic variability of high-frequency SiO maser emission.
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Hodge, T. M., C. E. Woodward, D. M. Kelly, J. Fischer, M. A. Greenhouse, S. Satyapal, H. A. Smith, J. L. Pipher y W. J. Forrest. "Near-IR emission line imaging of PN". Symposium - International Astronomical Union 180 (1997): 237. http://dx.doi.org/10.1017/s0074180900130578.
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Spatial studies of the emission line regions in planetary nebulae (PN) can provide insight into the physical and chemical environments across the nebulae. In a collaborative effort by the coauthors, a K-band Fabry-Perot etalon has been coupled with an advanced 256 × 256 InSb focal plane array at the Wyoming Infrared Observatory 2.3m telescope. This system permits us to obtain spatially resolved, 0.24″/pixel, moderate spectral resolution (R ≈ 800), flux-density IR emission line images of astronomical sources. We obtained continuum-subtracted images of Br γ, HeI 2.06 μm, the 2-μm UIR features, and the 3.3 μm PAH dust feature in the PN NGC 6572, NGC 7027, and NGC 7662. One objective was to determine the spatial morphology of two unidentified emission lines, UIR1−2.199 μm, and UIR2−2.287 μm (Geballe et al. 1991). These UIR lines appear in the spectra of many PN (Hora et al. 1997) and in the Orion Nebula (Luhman & Rieke 1996). Geballe et al. suggested that the UIR lines are most likely forbidden transitions and showed that the parent ion ionization potential is ≈ 30–40 eV, while the ionization potential for the ions themselves is 40–60 eV. Here we directly compare the distribution of the UIR emitters to that of the gas (H+,He+) and dust (PAHs).
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Siebenmorgen, R., P. Scicluna y J. Krełowski. "Far-infrared emission of massive stars". Astronomy & Astrophysics 620 (23 de noviembre de 2018): A32. http://dx.doi.org/10.1051/0004-6361/201833546.
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We present results of the analysis of a sample of 22 stars of spectral types from O7 to B5 and luminosity classes I–V for which spectra from the Infrared Spectrograph (IRS) of Spitzer are available. The IRS spectra of these stars are examined for signs of excess infrared (IR) emission by comparison with stellar atmospheric spectra. We find that the spectra of half of the studied stars are dominated by excess emission in the far-IR, including all six super- and bright giants. In order to examine the origin of the far-IR excess, we supplement the Spitzer data with optical high-resolution echelle spectroscopy (λ∕Δλ ~ 105), near-IR high-contrast coronagraphic imaging taken with the SPHERE instrument at VLT with a spatial resolution of 0.′′05, and WISE and Herschel photometry. In the optical region, we detect various absorption and emission lines (H α, C III, and N III) irrespective of the far-IR excess. Pfund α and Humphrey α lines are observed at the same time as the far-IR excess. These lines are stronger in stars with far-IR excess than in stars without excess. A scattered-light disk in the central r ≲ 2.5′′ region of the far-IR excess stars HD 149404, HD 151804, and HD 154368 can be excluded from H band imaging down to a 1σ contrast of F(r)∕F∗~ 10−6. The far-IR excess is fit either by a free–free component from ionized gas as for the winds of hot stars or a large (1 pc) circumstellar dust shell. The putative dust envelopes required to explain the excess have a visual extinction as low as a few hundred μ-mag.
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Birkinshaw, M., D. M. Worrall y A. Bliss. "Dust heating in the cores of 3CRR radio galaxies". Proceedings of the International Astronomical Union 10, S313 (septiembre de 2014): 294–98. http://dx.doi.org/10.1017/s1743921315002355.
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AbstractWe have undertaken a Spitzer campaign to measure the IR structures and spectra of low-redshift 3CRR radio galaxies. The results show that the 3.6 – 160 μm infrared properties vary systematically with integrated source power, and so demonstrate that contemporary core activity is characteristic of the behaviour of sources over their lifetimes. IR synchrotron emission is seen from jets and hotspots in some cases. Thermal emission is found from a jet/gas interaction in NGC7385. Most of the near-IR integrated colours of the low-redshift 3CRR radio galaxies are similar to those of passive galaxies, so that IR colours are poor indicators of radio activity.
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Burton, Michael G., J. E. Howe, T. R. Geballe y P. W. J. L. Brand. "Near-IR Fluorescent Molecular Hydrogen Emission from NGC 2023". Publications of the Astronomical Society of Australia 15, n.º 2 (1998): 194–201. http://dx.doi.org/10.1071/as98194.
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AbstractSpectra from 1 to 2·5 μm, at 230–430 spectral resolution, are presented of the fluorescent molecular hydrogen line emission from two locations in the reflection nebula NGC 2023. Over 100 H2 lines can be identified in the spectra, although blending and poor atmospheric transmission mean that reliable level column densities can only be obtained from 35 lines. This latter group includes lines from v = 1–8 and v = 10, spanning an energy range from 6000 to 45,000 K above the ground state. These data may be used to constrain models of photodissociation regions and of fluorescent excitation for molecular hydrogen.
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Gangadhara, R. T. "Reception of Radio Waves from Pulsars". Symposium - International Astronomical Union 218 (2004): 343–44. http://dx.doi.org/10.1017/s0074180900181343.
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The beamed emission by relativistic sources moving along the magnetic dipolar field lines occurs in the direction of tangents to the field lines. To receive such a beamed radiation, the line of sight must align with the tangent within the beaming angle 1/γ, where γ is the particle Lorentz factor. By solving the viewing geometry, in an inclined and rotating dipole magnetic field, we show that at any given pulse phase the observer can receive the radiation only from specific altitudes. We find that the outer conal emission is received from higher altitudes than the inner conal components including the core. At any pulse phase, low frequency emission comes from the higher altitudes than higher-frequency emission. As an application of our model, we have used it to explain the emission heights of conal components in PSR B0329+54.
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Gao, Rui Feng, Yuan Yuan Du y Pei Yang. "Determination of Iridium in Platinum Jewelry Alloys by ICP-AES". Applied Mechanics and Materials 79 (julio de 2011): 248–53. http://dx.doi.org/10.4028/www.scientific.net/amm.79.248.
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A method for the determination of iridium impurity in platinum jewelry alloys by inductively coupled plasma atomic emission spectrometry (ICP-AES) was reported. Spectral interferences of Au, Cr, Cu, Fe, Ni and Pt to Ir at specific wavelengths have been investigated. The spectral coincidence profiles were recorded and interfering lines were identified. The optimum analytical line of 38 iridium emission lines was 215.268 nm {156}. Ir 212.681 {158} and Ir 205.116 nm {164} can be used as analytical lines after rectified by Inter-Element Corrections (IEC) coefficients. Ir 186.250 nm is a new candidate analytical line. Ir 224.268 nm is not being recommended by reason of the severe spectral interference from Cu and Ni. Ir 322.08 nm is not being recommended for its weaker emission intensity. Validation was performed in terms of detection limits, linearity, precision and recovery. The relative standard deviations (RSD) and recoveries of the method are in the range of 0.59%~1.84% and 85.5%~93.2%, respectively.
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Seaquist, E. R. "The Radio Properties of Symbiotic Stars". International Astronomical Union Colloquium 103 (1988): 69–75. http://dx.doi.org/10.1017/s0252921100103173.
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AbstractRadio thermal bremsstrahlung emission has now been detected at centimeter wavelengths from about thirty symbiotic stars. These data combined with optical and IR data show that the radio emission in most systems may be understood in terms of the ionization of part of the wind of a red giant by a hot companion. The radio properties of symbiotic stars are reviewed and the agreement with and the limitations of this picture are examined.
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Plotkin, Richard M., Scott F. Anderson, W. N. Brandt, Aleksandar M. Diamond-Stanic, Xiaohui Fan, Chelsea L. MacLeod, Donald P. Schneider y Ohad Shemmer. "MULTIWAVELENGTH OBSERVATIONS OF RADIO-QUIET QUASARS WITH WEAK EMISSION LINES". Astrophysical Journal 721, n.º 1 (30 de agosto de 2010): 562–75. http://dx.doi.org/10.1088/0004-637x/721/1/562.
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Wills, K. A., R. Morganti, C. N. Tadhunter, T. G. Robinson y M. Villar-Martin. "Emission lines and optical continuum in low-luminosity radio galaxies". Monthly Notices of the Royal Astronomical Society 347, n.º 3 (21 de enero de 2004): 771–86. http://dx.doi.org/10.1111/j.1365-2966.2004.07195.x.
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Pascucci, I., U. Gorti y D. Hollenbach. "FREE-FREE EMISSION AND RADIO RECOMBINATION LINES FROM PHOTOEVAPORATING DISKS". Astrophysical Journal 751, n.º 2 (17 de mayo de 2012): L42. http://dx.doi.org/10.1088/2041-8205/751/2/l42.
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