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Journal articles on the topic 'Techniques: photometric'

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Published: 4 June 2021

Last updated: 9 June 2025

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Tinbergen, Jaap. "New Techniques." International Astronomical Union Colloquium 136 (1993): 130–46. http://dx.doi.org/10.1017/s025292110000748x.

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AbstractRoutine millimagnitude photometry may require a new approach to reduction of photometric errors. Such an approach is outlined in this paper; it stresses elimination of each error as close to its source as possible. The possibilities provided by modern technology are reviewed in this light. An engineering design group dedicated to photometry is a prerequisite and an on-site photometric technician may be necessary. In this concept, observers are mainly remote users of a database. Implied is the idea of accurate photometry necessarily developing into a single but multi-site astronomical facility (cf. VLBI) and the communal discipline that goes with it.

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Walker, Alistair, Saul Adelman, Eugene Milone, Barbara Anthony-Twarog, Pierre Bastien, Wen Ping Chen, Steve Howell, et al. "DIVISION B COMMISSION 25: ASTRONOMICAL PHOTOMETRY AND POLARIMETRY." Proceedings of the International Astronomical Union 11, T29A (August 2015): 159–70. http://dx.doi.org/10.1017/s1743921316000727.

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Commission 25 (C25) deals with the techniques and issues involved with the measurement of optical and infrared radiation intensities and polarization from astronomical sources. As such, in recent years attention has focused on photometric standard stars, atmospheric extinction, photometric passbands, transformation between systems, nomenclature, and observing and reduction techniques. At the start of the trimester C25 changed its name from Stellar Photometry and Polarization to Astronomical Photometry and Polarization so as to explicitly include in its mandate particular issues arising from the measurement of resolved sources, given the importance of photometric redshifts of distant galaxies for many of the large photometric surveys now underway. We begin by summarizing commission activities over the 2012-2014 period, follow with a report on Polarimetry, continue with Photometry topics that have been of interest to C25 members, and conclude with a Vision for the Future.

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Davies, L. J. M., J. E. Thorne, A. S. G. Robotham, S. Bellstedt, S. P. Driver, N. J. Adams, M. Bilicki, et al. "Deep Extragalactic VIsible Legacy Survey (DEVILS): consistent multiwavelength photometry for the DEVILS regions (COSMOS, XMMLSS, and ECDFS)." Monthly Notices of the Royal Astronomical Society 506, no. 1 (June 5, 2021): 256–87. http://dx.doi.org/10.1093/mnras/stab1601.

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ABSTRACT The Deep Extragalactic VIsible Legacy Survey (DEVILS) is an ongoing high-completeness, deep spectroscopic survey of ∼60 000 galaxies to Y &lt; 21.2 mag, over ∼6 deg2 in three well-studied deep extragalactic fields: D10 (COSMOS), D02 (XMMLSS), and D03 (ECDFS). Numerous DEVILS projects all require consistent, uniformly derived and state-of-the-art photometric data with which to measure galaxy properties. Existing photometric catalogues in these regions either use varied photometric measurement techniques for different facilities/wavelengths leading to inconsistencies, older imaging data and/or rely on source detection and photometry techniques with known problems. Here, we use the ProFound image analysis package and state-of-the-art imaging data sets (including Subaru-HSC, VST-VOICE, VISTA-VIDEO, and UltraVISTA-DR4) to derive matched-source photometry in 22 bands from the FUV to 500 $\mu$m. This photometry is found to be consistent, or better, in colour analysis to previous approaches using fixed-size apertures (which are specifically tuned to derive colours), but produces superior total source photometry, essential for the derivation of stellar masses, star formation rates, star formation histories, etc. Our photometric catalogue is described in detail and, after internal DEVILS team projects, will be publicly released for use by the broader scientific community.

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Goodeve, Joshua L. "Light Streak Photometry and Streaktools." Astronomical Journal 169, no. 3 (February 18, 2025): 151. https://doi.org/10.3847/1538-3881/ada950.

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Abstract The accuracy of photometric calibration has gradually become a limiting factor in various fields of astronomy, limiting the scientific output of a host of research. Calibration using artificial light sources in low Earth orbit remains largely unexplored. Here, we demonstrate that photometric calibration using light sources in low Earth orbit is a viable and competitive alternative/complement to current calibration techniques, and explore the associated ideas and basic theory. We present the publicly available Python code Streaktools as a means to simulate and perform photometric calibration using real and simulated light streaks. Using Streaktools, we perform “pill” aperture photometry on 131 simulated streaks, and Markov chain Monte Carlo based point-spread-function (PSF) model-fitting photometry on 425 simulated streaks in an attempt to recover the magnitude zeropoint of a real exposure of the Dark Energy Camera instrument on the Blanco 4 m telescope. Our results show that calibration using pill photometry is too inaccurate to be useful, but that PSF photometry is able to produce unbiased and accurate (1σ error = 3.4 mmag) estimates of the zeropoint of a real image in a realistic scenario, with a reasonable light source. This demonstrates that light-streak photometry is a promising alternative and complement to established techniques, which should be explored and tested further.

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Cabayol-Garcia, L., M. Eriksen, A. Alarcón, A. Amara, J. Carretero, R. Casas, F. J. Castander, et al. "The PAU Survey: background light estimation with deep learning techniques." Monthly Notices of the Royal Astronomical Society 491, no. 4 (November 23, 2019): 5392–405. http://dx.doi.org/10.1093/mnras/stz3274.

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ABSTRACT In any imaging survey, measuring accurately the astronomical background light is crucial to obtain good photometry. This paper introduces BKGnet, a deep neural network to predict the background and its associated error. BKGnet has been developed for data from the Physics of the Accelerating Universe Survey (PAUS), an imaging survey using a 40 narrow-band filter camera (PAUCam). The images obtained with PAUCam are affected by scattered light: an optical effect consisting of light multiply reflected that deposits energy in specific detector regions affecting the science measurements. Fortunately, scattered light is not a random effect, but it can be predicted and corrected for. We have found that BKGnet background predictions are very robust to distorting effects, while still being statistically accurate. On average, the use of BKGnet improves the photometric flux measurements by $7{{\ \rm per\ cent}}$ and up to $20{{\ \rm per\ cent}}$ at the bright end. BKGnet also removes a systematic trend in the background error estimation with magnitude in the i band that is present with the current PAU data management method. With BKGnet, we reduce the photometric redshift outlier rate by $35{{\ \rm per\ cent}}$ for the best $20{{\ \rm per\ cent}}$ galaxies selected with a photometric quality parameter.

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Lee, Bomee, and Ranga-Ram Chary. "Improved photometric redshifts with colour-constrained galaxy templates for future wide-area surveys." Monthly Notices of the Royal Astronomical Society 497, no. 2 (July 17, 2020): 1935–45. http://dx.doi.org/10.1093/mnras/staa2100.

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ABSTRACT Cosmology and galaxy evolution studies with LSST, Euclid, and Roman, will require accurate redshifts for the detected galaxies. In this study, we present improved photometric redshift estimates for galaxies using a template library that populates three-colour space and is constrained by HST/CANDELS photometry. For the training sample, we use a sample of galaxies having photometric redshifts that allows us to train on a large, unbiased galaxy sample having deep, unconfused photometry at optical-to-mid infrared wavelengths. Galaxies in the training sample are assigned to cubes in 3D colour space, V − H, I − J, and z − H. We then derive the best-fitting spectral energy distributions of the training sample at the fixed CANDELS median photometric redshifts to construct the new template library for each individual colour cube (i.e. colour-cube-based template library). We derive photometric redshifts (photo-z) of our target galaxies using our new colour-cube-based template library and with photometry in only a limited set of bands, as expected for the aforementioned surveys. As a result, our method yields σNMAD of 0.026 and an outlier fraction of 6 per cent using only photometry in the LSST and Euclid/Roman bands. This is an improvement of ∼10 per cent on σNMAD and a reduction in outlier fraction of ∼13 per cent compared to other techniques. In particular, we improve the photo-z precision by about 30 per cent at 2 &lt; z &lt; 3. We also assess photo-z improvements by including K or mid-infrared bands to the ugrizYJH photometry. Our colour-cube-based template library is a powerful tool to constrain photometric redshifts for future large surveys.

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Rau, M. M., C. B. Morrison, S. J. Schmidt, S. Wilson, R. Mandelbaum, Y.-Y. Mao, David Alonso, et al. "A composite likelihood approach for inference under photometric redshift uncertainty." Monthly Notices of the Royal Astronomical Society 509, no. 4 (November 12, 2021): 4886–907. http://dx.doi.org/10.1093/mnras/stab3290.

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ABSTRACT Obtaining accurately calibrated redshift distributions of photometric samples is one of the great challenges in photometric surveys like LSST, Euclid, HSC, KiDS, and DES. We present an inference methodology that combines the redshift information from the galaxy photometry with constraints from two-point functions, utilizing cross-correlations with spatially overlapping spectroscopic samples, and illustrate the approach on CosmoDC2 simulations. Our likelihood framework is designed to integrate directly into a typical large-scale structure and weak lensing analysis based on two-point functions. We discuss efficient and accurate inference techniques that allow us to scale the method to the large samples of galaxies to be expected in LSST. We consider statistical challenges like the parametrization of redshift systematics, discuss and evaluate techniques to regularize the sample redshift distributions, and investigate techniques that can help to detect and calibrate sources of systematic error using posterior predictive checks. We evaluate and forecast photometric redshift performance using data from the CosmoDC2 simulations, within which we mimic a DESI-like spectroscopic calibration sample for cross-correlations. Using a combination of spatial cross-correlations and photometry, we show that we can provide calibration of the mean of the sample redshift distribution to an accuracy of at least 0.002(1 + z), consistent with the LSST-Y1 science requirements for weak lensing and large-scale structure probes.

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Zhang, Yan-Xia, and Yong-Heng Zhao. "Photometric Redshift Techniques in Big-data Era." Proceedings of the International Astronomical Union 11, S319 (August 2015): 57. http://dx.doi.org/10.1017/s1743921315009886.

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AbstractPhotometric data increase with large survey projects running. The huge volume of data influences the means and methods to deal with them. As such, the techniques of photometric redshift estimation based on photometric data must be developed and improved.

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Ackermann, Jens, and Michael Goesele. "A Survey of Photometric Stereo Techniques." Foundations and Trends® in Computer Graphics and Vision 9, no. 3-4 (2015): 149–254. http://dx.doi.org/10.1561/0600000065.

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Tian, Jun, Haibin Zhao, Bin Li, Yongxiong Zhang, Jian Chen, Leonid Elenin, and Xiaoping Lu. "Photometry and Models of Seven Main-Belt Asteroids." Universe 10, no. 10 (October 14, 2024): 395. http://dx.doi.org/10.3390/universe10100395.

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The China Near-Earth Object Survey Telescope (CNEOST) conducted four photometric surveys from 2015 to 2018 using image processing and aperture photometry techniques to obtain extensive light curve data on asteroids. The second-order Fourier series method was selected for its efficiency in determining the rotation periods of the observed asteroids. Our study successfully derived rotation periods for 892 asteroids, with 648 of those matching values recorded in the LCDB (for asteroids with U > 2). To enhance the reliability of the derived spin parameters and shape models, we also amassed a comprehensive collection of published light curve data supplemented by additional photometric observations on a targeted subset of asteroids conducted using multiple telescopes between 2021 and 2022. Through the application of convex inversion techniques, we successfully derived spin parameters and shape models for seven main-belt asteroids (MBAs): (2233) Kuznetsov, (2294) Andronikov, (2253) Espinette, (4796) Lewis, (1563) Noel, (2912) Lapalma, and (5150) Fellini. Our thorough analysis identified two credible orientations for the rotational poles of these MBAs, shedding light on the prevalent issue of “ambiguity in pole direction” that often accompanies photometric inversion processes. CNEOST continues its observational endeavors, and future collected data combined with other independent photometric measurements will facilitate further inversion to better constrain the spin parameters and yield more refined shape models.

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Glass, I. S. "Photometry with Infrared Arrays." International Astronomical Union Colloquium 136 (1993): 154–59. http://dx.doi.org/10.1017/s0252921100007508.

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AbstractInfrared arrays have been in use at a number of observatories for several years. They are more complicated in their construction than optical ones and more problems arise in obtaining good photometry from them. The types of arrays currently available are described together with the observational techniques and the problems encountered in obtaining accurate photometric results.

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Cachero, Rocio, and Carlota Abello. "Stereo-photometric techniques for scanning micrometer scale." Virtual Archaeology Review 6, no. 13 (November 24, 2015): 72. http://dx.doi.org/10.4995/var.2015.4380.

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This paper describes a new methodology based on the combination of photogrammetric and stereo-photometric techniques that allows creating virtual replicas reproducing the relief in micrometric scale, with a geometric resolution until 7 microns. The finest details of the texture obtained by photogrammetric methods are translated to the relief of the mesh to provide quality 3D printing by additive manufacturing methods. These results open new possibilities for virtual and physical reproduction of archeological items that need a great accuracy and geometric resolution.

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Subbarao, M. U., A. J. Connolly, A. S. Szalay, and D. C. Koo. "Luminosity Functions From Photometric Redshifts. I. Techniques." Astronomical Journal 112 (September 1996): 929. http://dx.doi.org/10.1086/118066.

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Newling, J., M. Varughese, B. Bassett, H. Campbell, R. Hlozek, M. Kunz, H. Lampeitl, et al. "Statistical classification techniques for photometric supernova typing." Monthly Notices of the Royal Astronomical Society 414, no. 3 (April 15, 2011): 1987–2004. http://dx.doi.org/10.1111/j.1365-2966.2011.18514.x.

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Chang, Kimmy, Alex Cabello, Jeff Houchard, Jonathan Gazak, and Justin Fletcher. "Leveraging Synthetic Data for Star and Satellite Photometry." American Journal of Optics and Photonics 12, no. 2 (September 29, 2024): 18–29. http://dx.doi.org/10.11648/j.ajop.20241202.11.

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In the realm of Space Domain Awareness (SDA), precise photometric measurements are essential for applications such as stability analysis, shape recovery, and material studies of satellites. However, current methods that rely on manual data collection and analysis are not scalable to autonomous frameworks, which are increasingly necessary due to the growing congestion in space. This research presents an approach to automate photometric measurements within a network of telescopes operating in non-ideal conditions. Our work focuses on achieving reliable photometry in degraded weather conditions, where traditional methods might fail, leading to false detections and unnecessary follow-up efforts. We utilize the SatSim space scene simulator to generate synthetic data for training and testing photometry algorithms. These algorithms include both traditional aperture photometry and machine learning-based approaches. Our methodology employs dynamic segmentation techniques to optimize the detection of satellites and stars under various adverse conditions. The segmentation methods were evaluated for their robustness in different scenarios, with the Depth-First Search + Interquartile Range (DFS + IQR) approach showing the most promise. Through extensive experimentation, we demonstrate that our approach can achieve a photometric precision of approximately 10&lt;sup&gt;−1&lt;/sup&gt;, even in adverse conditions. This represents a significant advancement in the field, as it enables more reliable satellite detection and tracking in real-world, non-photometric environments. Additionally, our ablation studies highlight the importance of balanced datasets in reducing error metrics, particularly for underrepresented satellite classes. This work contributes to the development of more effective autonomous SDA systems, capable of operating efficiently in a wide range of environmental conditions.

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Jewitt, D. "Cometary Photometry." International Astronomical Union Colloquium 116, no. 1 (1989): 19–65. http://dx.doi.org/10.1017/s0252921100109625.

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AbstractThe study of comets using modern optical photometric techniques is reviewed. Particular emphasis is given to the physical constraints imposed on the nature of comets by photometric data. The photometric study of bare nuclei and of active comets is discussed.

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Strassmeier, Klaus G. "The zoo of starspots." Proceedings of the International Astronomical Union 6, S273 (August 2010): 174–80. http://dx.doi.org/10.1017/s1743921311015201.

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AbstractStarspots are being observed with many different techniques but not always with coherent results. In particular not if model-dependent data analysis must be employed, e.g. through two-dimensional spot modelling of one-dimensional photometric light curves. I review the zoo of currently available physical spot parameters, i.e. their size, temperature and variability time scales, and also compare results from different techniques. Most of the current values come from Doppler imaging and multi-color photometry. I also list a few cases where starspot detections turned out to be very different to the solar analog.

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Hudgins, David W., and Miroslav D. Filipović. "Photometric Techniques Using Small College Research Instruments for Study of the Extrasolar Planetary Transits of HD 209458." Publications of the Astronomical Society of Australia 19, no. 4 (2002): 443–47. http://dx.doi.org/10.1071/as02007.

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AbstractWe present the results of a program to develop techniques that enable high-resolution photometric measurements using modest research instruments available to small colleges, and then demonstrate those techniques in a pilot photometric project.Using a 25 cm Schmidt–Cassegrain telescope and SBIG ST7E CCD camera, we develop techniques that enabled milli-magnitude photometric resolution. The pilot project studied five transits of the recently discovered gas giant planet orbiting HD 209458. We measured a flux drop of 1.46 ± 0.17% during the transit which corresponds to a planetary diameter of 1.39 ± 0.14 RJup, a transit period of 2h 48min ± 21min, and planet orbital inclination of 87.6 ± 1.3°. We determined the orbital period as 3.5234 ± 0.0026 days. These results agree well with other studies which used professional grade research instruments. We suggest a number of other challenging photometric research areas suitable for graduate and undergraduate investigation using equipment common to many small colleges.

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Merlin, E., M. Castellano, P. Santini, G. Cipolletta, K. Boutsia, C. Schreiber, F. Buitrago, et al. "The ASTRODEEP-GS43 catalogue: New photometry and redshifts for the CANDELS GOODS-South field." Astronomy & Astrophysics 649 (May 2021): A22. http://dx.doi.org/10.1051/0004-6361/202140310.

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Context. We present ASTRODEEP-GS43, a new multi-wavelength photometric catalogue of the GOODS-South field, which builds and improves upon the previously released CANDELS catalogue. Aims. We provide photometric fluxes and corresponding uncertainties in 43 optical and infrared bands (25 wide and 18 medium filters), as well as the photometric redshifts and physical properties of the 34930 CANDELS H-detected objects, plus an additional sample of 178 H-dropout sources, of which 173 are Ks-detected and five are IRAC-detected. Methods. We keep the CANDELS photometry in seven bands (CTIO U, Hubble Space Telescope WFC3, and ISAAC-K) and measure from scratch the fluxes in the other 36 (23 from Subaru SuprimeCAM and Magellan Baade FourStar and the rest from VIMOS, HST ACS, HAWK-I Ks, and Spitzer IRAC) with state-of-the-art template-fitting techniques. We then compute new photometric redshifts with three different software tools and take the median value as a best estimate. We finally evaluate new physical parameters from spectral energy distribution (SED) fitting, comparing them to previously published ones. Results. Comparing to a sample of 3931 high quality spectroscopic redshifts, for the new photometric redshifts we obtain a normalised median absolute deviation of 0.015, with 3.01% of outliers on the full catalogue (0.011 and 0.22% on the bright end at I814 < 22.5). This is similar to the best available published samples of photometric redshifts, such as the COSMOS UltraVISTA catalogue. Conclusions. The ASTRODEEP-GS43 results are in qualitative agreement with previously published catalogues of the GOODS-South field, improving on them particularly in terms of SED sampling and photometric redshift estimates. The catalogue is available for download from the ASTRODEEP website.

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Read, S. C., D. J. B. Smith, M. J. Jarvis, and G. Gürkan. "The performance of photometric reverberation mapping at high redshift and the reliability of damped random walk models." Monthly Notices of the Royal Astronomical Society 492, no. 3 (December 20, 2019): 3940–59. http://dx.doi.org/10.1093/mnras/stz3574.

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ABSTRACT Accurate methods for reverberation mapping using photometry are highly sought after since they are inherently less resource intensive than spectroscopic techniques. However, the effectiveness of photometric reverberation mapping for estimating black hole masses is sparsely investigated at redshifts higher than z ≈ 0.04. Furthermore, photometric methods frequently assume a damped random walk (DRW) model, which may not be universally applicable. We perform photometric reverberation mapping using the javelin photometric DRW model for the QSO SDSS-J144645.44+625304.0 at z = 0.351 and estimate the Hβ lag of $65^{+6}_{-1}$ d and black hole mass of $10^{8.22^{+0.13}_{-0.15}}\, \mathrm{M_{\odot }}$. An analysis of the reliability of photometric reverberation mapping, conducted using many thousands of simulated CARMA process light curves, shows that we can recover the input lag to within 6 per cent on average given our target’s observed signal-to-noise of &gt;20 and average cadence of 14 d (even when DRW is not applicable). Furthermore, we use our suite of simulated light curves to deconvolve aliases and artefacts from our QSO’s posterior probability distribution, increasing the signal-to-noise on the lag by a factor of ∼2.2. We exceed the signal-to-noise of the Sloan Digital Sky Survey Reverberation Mapping Project (SDSS-RM) campaign with a quarter of the observing time per object, resulting in a ∼200 per cent increase in signal-to-noise efficiency over SDSS-RM.

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Butler, R. F., A. Shearer, R. M. Redfern, M. Colhoun, P. O'Kane, A. J. Penny, P. W. Morris, W. K. Griffiths, and M. Cullum. "TRIFFID photometry of globular cluster cores - I. Photometric techniques and variable stars in M15." Monthly Notices of the Royal Astronomical Society 296, no. 2 (May 11, 1998): 379–91. http://dx.doi.org/10.1046/j.1365-8711.1998.01359.x.

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Koornneef, J., R. Bohlin, R. Buser, K. Horne, and D. Turnshek. "Synthetic Photometry and the Calibration of the Hubble Space Telescope." Highlights of Astronomy 7 (1986): 833–43. http://dx.doi.org/10.1017/s153929960000736x.

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AbstractThe combined Scientific Instruments (SIs) on the Hubble Space Telescope (HST) feature an extensive wavelength coverage in both photometric and spectrophotometric modes with an overall dynamic range of more than twenty-five magnitudes. We demonstrate how synthetic photometry techniques are to be used to establish and maintain their calibration. This approach makes efficient use of limited HST observing time by taking full advantage of pre-launch knowledge on the SI sensitivity functions and calibration targets.

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Wilson, Richard, and Heide Friedrich. "Coupling of Ultrasonic and Photometric Techniques for Synchronous Measurements of Unconfined Turbidity Currents." Water 10, no. 9 (September 14, 2018): 1246. http://dx.doi.org/10.3390/w10091246.

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By synchronizing data collection, such as photometric and ultrasonic Doppler profiling (UVP) measurement techniques, new insights can be obtained into environmental flows, such as highly dynamic turbidity currents. We introduce a combined experimental setup, which ultimately allows a time reduction in testing programmes, and discuss the measurement advances with the help of four surface conditions we tested for unconfined turbidity currents: (a) a smooth surface; (b) a smooth surface with an obstacle present; (c) a rough surface; and (d) a rough surface with an obstacle present. We show that data from both measurement techniques indicate that a rough surface reduces global current velocities and the magnitude of turbidity current phenomena, including Kelvin-Helmholtz instabilities and lobe-and-cleft formation. However, by coupling the techniques, photometric data give valuable insight into the spatial development of instabilities, such as the grouping of lobe and cleft formations. The presence of an obstacle causes local regions of an increased and decreased velocity, but does not affect the global current velocity. Additionally, the obstacle created three local intensity maxima upstream, dissipating to two maxima downstream, supporting the presence of local eddies. The study shows that the combination of UVP and photometry is an effective way forward for obtaining detailed qualitative and quantitative insights into turbulent flow characteristics and we highlight the potential for future research.

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Stritzinger, M. D., J. P. Anderson, C. Contreras, E. Heinrich-Josties, N. Morrell, M. M. Phillips, J. Anais, et al. "The Carnegie Supernova Project I." Astronomy & Astrophysics 609 (January 2018): A134. http://dx.doi.org/10.1051/0004-6361/201730842.

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The first phase of the Carnegie Supernova Project (CSP-I) was a dedicated supernova follow-up program based at the Las Campanas Observatory that collected science data of young, low-redshift supernovae between 2004 and 2009. Presented in this paper is the CSP-I photometric data release of low-redshift stripped-envelope core-collapse supernovae. The data consist of optical (uBgVri) photometry of 34 objects, with a subset of 26 having near-infrared (YJH) photometry. Twenty objects have optical pre-maximum coverage with a subset of 12 beginning at least five days prior to the epoch of B-band maximum brightness. In the near-infrared, 17 objects have pre-maximum observations with a subset of 14 beginning at least five days prior to the epoch of J-band maximum brightness. Analysis of this photometric data release is presented in companion papers focusing on techniques to estimate host-galaxy extinction and the light-curve and progenitor star properties of the sample. The analysis of an accompanying visual-wavelength spectroscopy sample of ~150 spectra will be the subject of a future paper.

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Cho, Hanjin, Siwoo Lee, and Byoungho Lee. "Optical design of photometric techniques for specular reflection." Optics and Lasers in Engineering 151 (April 2022): 106882. http://dx.doi.org/10.1016/j.optlaseng.2021.106882.

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Anderson, Jay. "Photometric Techniques for Exploring Multiple Populations in Clusters." Proceedings of the International Astronomical Union 10, H16 (August 2012): 239–40. http://dx.doi.org/10.1017/s1743921314005584.

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AbstractThe advent of the Hubble Space Telescope (HST) and the development of new photometric algorithms that take advantage of its stable observing platform above the atmosphere have allowed us to study the populations in globular clusters with very high precision.

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Lumme, K., J. Peltoniemi, and W. M. Irvine. "Some photometric techniques for atmosphereless solar system bodies." Advances in Space Research 10, no. 1 (January 1990): 187–93. http://dx.doi.org/10.1016/0273-1177(90)90103-7.

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Chen, Bin, and Qingyu Peng. "Photometric techniques in mutual events of Galilean satellites." Chinese Journal of Space Science 31, no. 3 (2011): 338. http://dx.doi.org/10.11728/cjss2011.03.338.

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Karami, A., F. Menna, and F. Remondino. "INVESTIGATING 3D RECONSTRUCTION OF NON-COLLABORATIVE SURFACES THROUGH PHOTOGRAMMETRY AND PHOTOMETRIC STEREO." International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLIII-B2-2021 (June 28, 2021): 519–26. http://dx.doi.org/10.5194/isprs-archives-xliii-b2-2021-519-2021.

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Abstract. 3D digital reconstruction techniques are extensively used for quality control purposes. Among them, photogrammetry and photometric stereo methods have been for a long time used with success in several application fields. However, generating highly-detailed and reliable micro-measurements of non-collaborative surfaces is still an open issue. In these cases, photogrammetry can provide accurate low-frequency 3D information, whereas it struggles to extract reliable high-frequency details. Conversely, photometric stereo can recover a very detailed surface topography, although global surface deformation is often present. In this paper, we present the preliminary results of an ongoing project aiming to combine photogrammetry and photometric stereo in a synergetic fusion of the two techniques. Particularly, hereafter, we introduce the main concept design behind an image acquisition system we developed to capture images from different positions and under different lighting conditions as required by photogrammetry and photometric stereo techniques. We show the benefit of such a combination through some experimental tests. The experiments showed that the proposed method recovers the surface topography at the same high-resolution achievable with photometric stereo while preserving the photogrammetric accuracy. Furthermore, we exploit light directionality and multiple light sources to improve the quality of dense image matching in poorly textured surfaces.

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Barry, D. J., W. G. Bagnuolo, B. D. Mason, H. A. McAlister, and N. H. Turner. "Prospects for Rapid, Routine Speckle Photometry." International Astronomical Union Colloquium 135 (1992): 537–39. http://dx.doi.org/10.1017/s0252921100007077.

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Image reconstruction techniques have rapidly matured over the last decade, and increasing reference to full–aperture and masked aperture results appear in the literature. Although anomalies in morphology are understood, most work uses nonlinear iterative refinements of questionable photometric robustness. Recent development of linear least–squares phase reconstruction techniques from the bispectrum (Glindemann et al. 1991) offers hope for a robust technique using a computational tour de force. However, the field cannot be considered mature until routine photometry of a large number of speckle–resolved objects is performed and demonstrated to be repeatable. We review our work and our expectations for use of both computationally intensive and simple techniques in our routine speckle reductions.

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Maíz Apellániz, J., E. J. Alfaro, R. H. Barbá, G. Holgado, H. Vázquez-Ramió, J. Varela, A. Ederoclite, et al. "The GALANTE photometric survey of the northern Galactic plane: project description and pipeline." Monthly Notices of the Royal Astronomical Society 506, no. 3 (July 2, 2021): 3138–54. http://dx.doi.org/10.1093/mnras/stab1769.

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ABSTRACT The GALANTE optical photometric survey is observing the northern Galactic plane and some adjacent regions using seven narrow- and intermediate-filters, covering a total of 1618 deg2. The survey has been designed with multiple exposure times and at least two different air masses per field to maximize its photometric dynamic range, comparable to that of Gaia, and ensure the accuracy of its photometric calibration. The goal is to reach at least 1 per cent accuracy and precision in the seven bands for all stars brighter than AB magnitude 17 while detecting fainter stars with lower values of the signal-to-noise ratio. The main purposes of GALANTE are the identification and study of extinguished O+B+WR stars, the derivation of their extinction characteristics, and the cataloguing of F and G stars in the solar neighbourhood. Its data will be also used for a variety of other stellar studies and to generate a high-resolution continuum-free map of the Hα emission in the Galactic plane. We describe the techniques and the pipeline that are being used to process the data, including the basis of an innovative calibration system based on Gaia DR2 and 2MASS photometry.

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Kreidl, T. J. "Time-Series Photometry: CCDs vs. PMTs." International Astronomical Union Colloquium 136 (1993): 311–17. http://dx.doi.org/10.1017/s0252921100007703.

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AbstractWith the ability to obtain simultaneous photometry of many objects, CCD time-series photometry is a potentially powerful method for obtaining data, even under non-photometric conditions. In particular, the ability to utilize one or more comparison stars on the same frame without the need to move the telescope to a different field makes for a higher duty cycle than conventional photoelectric photometry. In addition, the ability to determine the local sky in a variety of ways plus the ability to use more complex analysis techniques such as profile fitting and curves of growth permits a variety of analysis options. Some of the advantages of utilizing CCDs and the techniques used in time-series photometry of compact objects are discussed. With the flexibility of modern CCD control systems, possibilities for real-time or near real-time data analysis using readily available computer technology are stressed. Brief discussions of periodicity analysis considerations and other aspects of the data acquisition are presented.

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Maireles-González, Òscar, Joan Bartrina-Rapesta, Miguel Hernández-Cabronero, and Joan Serra-Sagristà. "Lossy Compression of Integer Astronomical Images Preserving Photometric Properties*." Publications of the Astronomical Society of the Pacific 136, no. 11 (November 1, 2024): 114506. http://dx.doi.org/10.1088/1538-3873/ad8b69.

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Abstract Observatories are producing astronomical image data at quickly increasing rates. As a result, the efficiency of the compression methods employed is critical to meet the storage and distribution requirements of both observatories and scientists. This paper presents a novel lossy compression technique that is able to preserve the results of photometry analysis with high fidelity while improving upon the state of the art in terms of compression performance. The proposed compression pipeline combines a flexible bi-region quantization scheme with the lossless, dictionary-based, LPAQ9M encoder. The quantization process allows compression performance and photometric fidelity to be precisely tailored to different scientific requirements. A representative data set of 16-bit integer astronomical images produced by telescopes from all around the world has been employed to empirically assess its compression-fidelity trade-offs, and compare them to those of the de facto standard Fpack compressor. In these experiments, the widespread SExtractor software is employed as the ground truth for photometric analysis. Results indicate that after lossy compression with our proposed method, the decompressed data allows consistent detection of over 99% of all astronomical objects for all tested telescopes, maintaining the highest photometric fidelity (as compared to state of the art lossy techniques). When compared to the best configuration of Fpack (Hcompress lossy using 1 quantization parameter) at similar compression rates, our proposed method provides better photometry precision: 7.15% more objects are detected with magnitude errors below 0.01, and 9.13% more objects with magnitudes below SExtractor’s estimated measurement error. Compared to the best lossless compression results, the proposed pipeline allows us to reduce the compressed data set volume by up to 38.75% and 27.94% while maintaining 90% and 95%, respectively, of the detected objects with magnitude differences lower than 0.01 mag; and up to 18.93% while maintaining 90% of the detected objects with magnitude differences lower than the photometric measure error.

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Mélou, J., A. Laurent, C. Fritz, and J. D. Durou. "3D DIGITIZATION OF HERITAGE: PHOTOMETRIC STEREO CAN HELP." International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLVIII-2/W1-2022 (December 8, 2022): 145–52. http://dx.doi.org/10.5194/isprs-archives-xlviii-2-w1-2022-145-2022.

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Abstract. There are mainly two families of photographic 3D reconstruction. Photogrammetry techniques work according to the principle of triangulation, from the matching of different views, while photometric techniques link the appearance of a 3D point to the orientation of its normal, relative to the direction of the incident light. While photogrammetry allows to find the global shape of a 3D scene, if it is sufficiently textured, photometric techniques highlight the details of the relief, as long as the model linking the lighting to the shape and reflectance of the scene is sufficiently realistic. In order to avoid errors in the 3D models obtained, all the photographic techniques of 3D reconstruction have benefited, over the years, from algorithmic improvements that make them more and more robust to outliers or unreliable data. Moreover, the complementarity between these two types of approaches having been identified for a long time, many solutions have been proposed to merge them. Our work aims at providing the free and open-source photogrammetry software Meshroom with the benefits it could get from photometric stereo, particularly in the context of the 3D digitization of heritage, knowing that it is the only photometric technique for 3D reconstruction that has really proven itself.

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Stobie, R. S., D. Kilkenny, D. O’Donoghue, and A. Chen. "The Edinburgh-Cape Blue Object Survey." International Astronomical Union Colloquium 148 (1995): 280–91. http://dx.doi.org/10.1017/s0252921100022041.

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AbstractThe Edinburgh-Cape Blue Object Survey is a major survey to discover blue stellar objects brighter than B ∼ 18 in the southern sky. It covers an area of sky of 10,000 square degrees with |b| > 30° and δ < 0°. The blue stellar objects are selected by automatic techniques from U and B pairs of UK Schmidt Telescope plates scanned with the COSMOS measuring machine. Follow-up photometry and spectroscopy are being obtained with the SAAO telescopes to classify objects brighter than B = 16.5. This paper describes the survey, the techniques used to extract the blue stellar objects, the photometric accuracy, and the completeness of the survey.

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Cooke, Benjamin F., and Don Pollacco. "specphot: a comparison of spectroscopic and photometric exoplanet follow-up methods." Monthly Notices of the Royal Astronomical Society 495, no. 1 (May 8, 2020): 734–42. http://dx.doi.org/10.1093/mnras/staa1194.

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ABSTRACT We set out a simulation to explore the follow-up of exoplanet candidates. We look at comparing photometric (transit method) and spectroscopic (Doppler shift method) techniques using three instruments: Next-Generation Transit Survey, High-Accuracy Radial-velocity Planetary Search, and CORALIE. We take into account the precision of follow-up and required observing time in attempt to rank each method for a given set of planetary system parameters. The methods are assessed on two criteria: signal-to-noise ratio (S/N) of the detection and follow-up time before characterization. We find that different follow-up techniques are preferred for different regions of parameter space. For S/N, we find that the ratio of spectroscopic to photometric S/N for a given system goes like $R_{\rm p}/P^{{1}/{3}}$. For follow-up time, we find that photometry is favoured for the shortest period systems (&lt;10 d) as well as systems with small planet radii. Spectroscopy is then preferred for systems with larger radius, and thus more massive planets (given our assumed mass–radius relationship). Finally, we attempt to account for the availability of telescopes and weight the two methods accordingly.

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Duque-Arribas, C., D. Montes, H. M. Tabernero, J. A. Caballero, J. Gorgas, and E. Marfil. "Photometric Calibrations of M-dwarf Metallicity with Markov Chain Monte Carlo and Bayesian Inference." Astrophysical Journal 944, no. 1 (February 1, 2023): 106. http://dx.doi.org/10.3847/1538-4357/acacf6.

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Abstract Knowledge of stellar atmospheric parameters (T eff, log g , [Fe/H]) of M dwarfs can be used to constrain both theoretical stellar models and Galactic chemical evolutionary models, and guide exoplanet searches, but their determination is difficult due to the complexity of the spectra of their cool atmospheres. In our ongoing effort to characterize M dwarfs, and in particular their chemical composition, we carried out multiband photometric calibrations of metallicity for early- and intermediate-type M dwarfs. The third Gaia data release provides high-precision astrometry and three-band photometry. This information, combined with the 2MASS and CatWISE2020 infrared photometric surveys and a sample of 4919 M dwarfs with metallicity values determined with high-resolution spectroscopy by The Cannon and APOGEE spectra, allowed us to study the effect of the metallicity in color–color and color–magnitude diagrams. We divided this sample into two subsamples: we used 1000 stars to train the calibrations with Bayesian statistics and Markov Chain Monte Carlo techniques, and the remaining 3919 stars to check the accuracy of the estimations. We derived several photometric calibrations of metallicity applicable to M dwarfs in the range of −0.45 ≤ [Fe/H] ≤ + 0.45 dex and spectral types down to M5.0 V that yield uncertainties down to the 0.10 dex level. Lastly, we compared our results with other photometric estimations published in the literature for an additional sample of 46 M dwarfs in wide binary systems with FGK-type primary stars and found a great predictive performance.

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Andrade, Laerte, Alan W. Pereira, Marcelo Emilio, and Eduardo Janot-Pacheco. "Exploring the Variability of Three Be Stars with TESS Observations." Universe 11, no. 2 (February 18, 2025): 71. https://doi.org/10.3390/universe11020071.

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Be stars are rapidly rotating B-type stars surrounded by circumstellar disks formed from self-ejected material. Understanding the mechanisms driving mass ejection and disk formation, known as the Be phenomenon, requires a detailed investigation of their variability and underlying physical processes. In this study, we analyze the photometric, spectroscopic, and seismic characteristics of three Be stars—HD 212044, 28 Cyg, and HD 174237—using high-cadence data from the TESS mission and spectral data from the BeSS database. Photometric variability was analyzed through iterative prewhitening and wavelet techniques, revealing distinct frequency groups associated with non-radial pulsations (NRPs). Spectral data provided equivalent width measurements of the Hα line, which correlated with photometric changes, reflecting dynamic interactions between the stars and their disks. Seismic analysis identified core rotation rates and buoyancy travel times for HD 212044 and 28 Cyg, offering insights into internal stellar processes and angular momentum distribution. HD 212044 exhibits a strong negative correlation between photometric brightness and Hα equivalent width, whereas this correlation is weaker in the case of 28 Cyg. The findings for these two stars highlight the interplay between NRPs, rapid rotation, and circumstellar disk dynamics. In contrast, the case of HD 174237 presents an example of how a binary system with mass transfer and a B-type component is revealed when observed simultaneously with space-based photometry and ground-based spectroscopy, demonstrating the importance of distinguishing classical Be stars from interacting binaries.

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Landolt, A. U., P. Martinez, P. Bastien, S. Fabrika, R. Gilliland, F. Grundahl, C. Jordi, and U. Munari. "Commission 25: Stellar Photometry and Polarimetry." Proceedings of the International Astronomical Union 1, T26A (December 2005): 307–12. http://dx.doi.org/10.1017/s1743921306004753.

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AbstractEven a brief glance at astronomical journals indicates the breadth and depth of observational projects making use of photometric and polarimetric techniques. Examples of ongoing photometric and polarimetric research as related by Commission Members follows. I thank the Commission Members, acknowledged below, for their input.

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Altena, B., A. Mousivand, J. Mascaro, and A. Kääb. "POTENTIAL AND LIMITATIONS OF PHOTOMETRIC RECONSTRUCTION THROUGH A FLOCK OF DOVE CUBESATS." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-3/W3 (October 19, 2017): 7–11. http://dx.doi.org/10.5194/isprs-archives-xlii-3-w3-7-2017.

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When Earth observation satellite systems are designed, one typically prefers a sun-synchronous orbit. However, the first generations of cubesats from Planet were deployed out of the International Space Station (ISS) and therefore do not obey such an orbit. Their configuration samples at different local times within the mid-latitudes. Consequently, it is in theory possible to exploit photometric techniques and extract highly detailed topographic information. In this study we demonstrate and explore photometry based on Planet cubesat images for Tyndall glacier at the Southern Patagonian icefield, and Zhadang glacier situated on the Tibetan plateau.

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Maskoliunas, M., J. Zdanavičius, V. Čepas, A. Kazlauskas, R. P. Boyle, K. Zdanavičius, K. Černis, K. Milašius, and M. Macijauskas. "New calibration of the Vilnius photometric system." Proceedings of the International Astronomical Union 14, A30 (August 2018): 486. http://dx.doi.org/10.1017/s1743921319005179.

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AbstractThe medium-band Vilnius photometric system with the mean wavelengths at 345 (U), 374 (P), 405 (X), 466 (Y), 516 (Z), 544 (V), and 656 (S) nm for many years was an important tool to determine interstellar reddenings and distances of single stars due to its ability to classify stars of all temperatures in spectral classes and luminosity classes in the presence of different interstellar reddenings. At present, Gaia DR2 presents distances to stars with an unprecedented accuracy at least up to 3 kpc. However, multicolor photometry, which allows the classification of stars as well as the preliminary determination of stellar temperatures, gravities, metallicities and interstellar reddenings, remains an important method for distant stars. Here we present an empirical calibration of the intrinsic color indices of the Vilnius system in terms of physical parameters of stars for dwarf and giant stars of spectral classes F-G-K-M. In any attempted photometric determination of physical parameters of stars it is important to have an extensive and homogeneous sample of spectroscopically determined parameters for stars for which there are also accurate photometric data. As a source catalogue for the Vilnius photometry the latest updated version of the Catalogue of Photoelectric Observations in the Vilnius System was used, which contains compilations from the published photometry for about 11 000 stars. The stars which had both the Gaia DR2 parallaxes and the determinations of stellar parameters from high-dispersion spectra were extracted from this catalogue. The final sample contains more than 1500 stars of spectral classes F-M. The majority of these stars (ca 70%) are not reddened, for others the values of interstellar reddening AV were determined using the regular techniques of photometric classification in the Vilnius system. The absolute magnitudes MV and consequently the luminosity classes were determined using Gaia DR2 parallaxes. We present the analytical expressions for the effective temperature Teff and surface gravity logg and evaluate the errors of solutions for dwarf and giant stars. To test the accuracy of the proposed method, we have compared our results with the stars observed by Gaia and with the stellar parameters available from the large spectroscopic surveys: APOGEE, Gaia-ESO, GALAH, LAMOST, RAVE and SEGUE. The results of comparison contain 5-6 % outliers.The proposed method allows the fast and straightforward evaluation of stellar physical parameters for the stars observed in the Vilnius photometric system. Despite the fact, that the accuracy of determination is significantly lower than in the case of spectroscopic methods, the method described may be useful for distant faint stars, which are still inaccessible for spectroscopic observations.

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Curran, S. J. "QSO photometric redshifts from SDSS, WISE, and GALEX colours." Monthly Notices of the Royal Astronomical Society: Letters 493, no. 1 (January 21, 2020): L70—L75. http://dx.doi.org/10.1093/mnrasl/slaa012.

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ABSTRACT Machine learning techniques, specifically the k-nearest neighbour algorithm applied to optical band colours, have had some success in predicting photometric redshifts of quasi-stellar objects (QSOs): Although the mean of differences between the spectroscopic and photometric redshifts, Δ$z$, is close to zero, the distribution of these differences remains wide and distinctly non-Gaussian. As per our previous empirical estimate of photometric redshifts, we find that the predictions can be significantly improved by adding colours from other wavebands, namely the near-infrared and ultraviolet. Self-testing this, by using half of the 33 643 strong QSO sample to train the algorithm, results in a significantly narrower spread in Δ$z$ for the remaining half of the sample. Using the whole QSO sample to train the algorithm, the same set of magnitudes return a similar spread in Δ$z$ for a sample of radio sources (quasars). Although the matching coincidence is relatively low (739 of the 3663 sources having photometry in the relevant bands), this is still significantly larger than from the empirical method (2 per cent) and thus may provide a method with which to obtain redshifts for the vast number of continuum radio sources expected to be detected with the next generation of large radio telescopes.

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Hviding, Raphael E., Kevin N. Hainline, Andy D. Goulding, and Jenny E. Greene. "Spectroscopic Confirmation of Obscured AGN Populations from Unsupervised Machine Learning." Astronomical Journal 167, no. 4 (March 19, 2024): 169. http://dx.doi.org/10.3847/1538-3881/ad28b4.

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Abstract We present the result of a spectroscopic campaign targeting active galactic nucleus (AGN) candidates selected using a novel unsupervised machine-learning (ML) algorithm trained on optical and mid-infrared photometry. AGN candidates are chosen without incorporating prior AGN selection criteria and are fainter, redder, and more numerous, ∼340 AGN deg−2, than comparable photometric and spectroscopic samples. In this work, we obtain 178 rest-optical spectra from two candidate ML-identified AGN classes with the Hectospec spectrograph on the MMT Observatory. We find that our first ML-identified group is dominated by Type I AGNs (85%) with a <3% contamination rate from non-AGNs. Our second ML-identified group is mostly comprised of Type II AGNs (65%), with a moderate contamination rate of 15% primarily from star-forming galaxies. Our spectroscopic analyses suggest that the classes recover more obscured AGNs, confirming that ML techniques are effective at recovering large populations of AGNs at high levels of extinction. We demonstrate the efficacy of pairing existing WISE data with large-area and deep optical/near-infrared photometric surveys to select large populations of AGNs and recover obscured growth of supermassive black holes. This approach is well suited to upcoming photometric surveys, such as Euclid, Rubin, and Roman.

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ITO, SHIN'ICHI. "Recycling. Physical Separation Techniques. Hand Picking and Photometric Sorting." Shigen-to-Sozai 113, no. 12 (1997): 908–11. http://dx.doi.org/10.2473/shigentosozai.113.908.

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Carlson, Paul J., and Thomas Urbanik. "Validation of Photometric Modeling Techniques for Retroreflective Traffic Signs." Transportation Research Record: Journal of the Transportation Research Board 1862, no. 1 (January 2004): 109–18. http://dx.doi.org/10.3141/1862-13.

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MACHIDA, Kenichiro, Harutaka IMOTO, and Takashi MAEKAWA. "1108 Development of Inspection System Using Photometric Stereo Techniques." Proceedings of Design & Systems Conference 2015.25 (2015): _1108–1_—_1108–6_. http://dx.doi.org/10.1299/jsmedsd.2015.25._1108-1_.

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Lapasset, E., M. Gomez, and R. Fariñas. "Test of the Optimization Techniques for the Photometric Analysis of Contact Binaries." Symposium - International Astronomical Union 151 (1992): 387–90. http://dx.doi.org/10.1017/s0074180900122545.

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We present light curve analyses of contact binaries and comparisons with previously published cross-correlations radial velocity data. The critical parameter q (mass-ratio) obtained from a grid technique is confronted with the spectroscopic value. For total eclipsing systems, both values are always in a good or reasonable agreement, including some stars with shallow light curves. For partial eclipsing systems, convergent photometric and spectroscopic results are obtained for an important set of stars. Two exceptions are V523 Cas and XY Boo for which some arguments are suggested. We concluded that reliable parameter determinations can be obtained from pure photometric solutions, by means of grid techniques.

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Han, Yunkun, Lulu Fan, Xian Zhong Zheng, Jin-Ming Bai, and Zhanwen Han. "BayeSED-GALAXIES. I. Performance Test for Simultaneous Photometric Redshift and Stellar Population Parameter Estimation of Galaxies in the CSST Wide-field Multiband Imaging Survey." Astrophysical Journal Supplement Series 269, no. 2 (November 15, 2023): 39. http://dx.doi.org/10.3847/1538-4365/acfc3a.

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Abstract The forthcoming Chinese Space Station Telescope (CSST) wide-field multiband imaging survey will produce seven-band photometric spectral energy distributions (SEDs) for billions of galaxies. The effective extraction of astronomical information from these massive data sets of SEDs relies on the techniques of SED synthesis (or modeling) and SED analysis (or fitting). We evaluate the performance of the latest version of the BayeSED code combined with SED models with increasing complexity for simultaneously determining the photometric redshifts and stellar population parameters of galaxies in this survey. By using an empirical statistics–based mock galaxy sample without SED modeling errors, we show that the random observational errors in photometries are more important sources of errors than the parameter degeneracies and Bayesian analysis method and tool. By using a Horizon-AGN hydrodynamical simulation–based mock galaxy sample with SED modeling errors about the star formation histories (SFHs) and dust attenuation laws (DALs), the simple typical assumptions lead to significantly worse parameter estimation with CSST photometries only. SED models with more flexible (or complicated) forms of SFH/DAL do not necessarily lead to better estimation of redshift and stellar population parameters. We discuss the selection of the best SED model by means of Bayesian model comparison in different surveys. Our results reveal that Bayesian model comparison with Bayesian evidence may favor SED models with different complexities when using photometries from different surveys. Meanwhile, the SED model with the largest Bayesian evidence tends to give the best performance of parameter estimation, which is clearer for photometries with higher discriminative power.

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Cavuoti, S., C. Tortora, M. Brescia, G. Longo, M. Radovich, N. R. Napolitano, V. Amaro, and C. Vellucci. "Cooperative photometric redshift estimation." Proceedings of the International Astronomical Union 12, S325 (October 2016): 166–72. http://dx.doi.org/10.1017/s1743921317001296.

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AbstractIn the modern galaxy surveys photometric redshifts play a central role in a broad range of studies, from gravitational lensing and dark matter distribution to galaxy evolution. Using a dataset of ~ 25,000 galaxies from the second data release of the Kilo Degree Survey (KiDS) we obtain photometric redshifts with five different methods: (i) Random forest, (ii) Multi Layer Perceptron with Quasi Newton Algorithm, (iii) Multi Layer Perceptron with an optimization network based on the Levenberg-Marquardt learning rule, (iv) the Bayesian Photometric Redshift model (or BPZ) and (v) a classical SED template fitting procedure (Le Phare). We show how SED fitting techniques could provide useful information on the galaxy spectral type which can be used to improve the capability of machine learning methods constraining systematic errors and reduce the occurrence of catastrophic outliers. We use such classification to train specialized regression estimators, by demonstrating that such hybrid approach, involving SED fitting and machine learning in a single collaborative framework, is capable to improve the overall prediction accuracy of photometric redshifts.

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Brooks, Hunter, Dan Caselden, J. Davy Kirkpatrick, Yadukrishna Raghu, Charles A. Elachi, Jake Grigorian, Asa Trek, et al. "Discovery of 118 New Ultracool Dwarf Candidates Using Machine-learning Techniques." Astronomical Journal 168, no. 5 (October 17, 2024): 211. http://dx.doi.org/10.3847/1538-3881/ad77d2.

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Abstract We present the discovery of 118 new ultracool dwarf candidates, discovered using a new machine-learning tool, named SMDET, applied to time-series images from the Wide-field Infrared Survey Explorer. We gathered photometric and astrometric data to estimate each candidate’s spectral type, distance, and tangential velocity. This sample has a photometrically estimated spectral class distribution of 28 M dwarfs, 64 L dwarfs, and 18 T dwarfs. We also identify a T-subdwarf candidate, two extreme T-subdwarf candidates, and two candidate young ultracool dwarfs. Five objects did not have enough photometric data for any estimations to be made. To validate our estimated spectral types, spectra were collected for two objects, yielding confirmed spectral types of T5 (estimated T5) and T3 (estimated T4). Demonstrating the effectiveness of machine-learning tools as a new large-scale discovery technique.

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