A Novel Technique to Improve Photometry in Confused Images Using Graphs and Bayesian Priors

Safarzadeh, Mohammadtaher; Ferguson, Henry C.; Lu, Yu; Inami, Hanae; Somerville, Rachel S.

doi:10.1088/0004-637x/798/2/91

Cited by 19 publications

(14 citation statements)

References 47 publications

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“…The persistent sparsity of these very high-z SMG samples is likely not only due to the intrinsic rarity of massive dusty galaxies in the early Universe, going along with the decrease in the star formation rate density to early times (Lilly et al 1996;Madau et al 1998;Madau & Dickinson 2014;Liu et al 2018), but also to incompleteness, i.e., missing detections of more typical objects at faint fluxes in heavily blended FIR/(sub)mm images. To counter these problems a number of new generation FIR catalogs have been built (Béthermin et al 2010(Béthermin et al , 2012(Béthermin et al , 2015Roseboom et al 2010;Elbaz et al 2011;Safarzadeh et al 2015;Hurley et al 2017;Lee et al 2013), that should allow in principle selection of DSFGs down to lower luminosities and up to highest redshifts. Notably, we have been developing new 'super-deblended' catalogs (Liu et al 2018;Jin et al 2018) that provide state-of-the-art FIR photometry with well behaved quasi-Gaussian uncertainties while limiting as much as possible the effects of blending from the poor IR PSFs of current ground-based facilities.…”

Section: Introductionmentioning

confidence: 99%

Discovery of Four Apparently Cold Dusty Galaxies at z = 3.62–5.85 in the COSMOS Field: Direct Evidence of Cosmic Microwave Background Impact on High-redshift Galaxy Observables

Jin

Daddi

Magdis

et al. 2019

ApJ

107

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We report Atacama Large Millimetre Array (ALMA) observations of four high-redshift dusty star-forming galaxy candidates selected from far-Infrared (FIR)/submm observations in the COSMOS field. We securely detect all galaxies in the continuum and spectroscopically confirm them at z=3.62-5.85 using ALMA 3mm line scans, detecting multiple CO and/or [CI] transitions. This includes the most distant dusty galaxy currently known in the COSMOS field, ID85001929 at z=5.847. These redshifts are lower than we had expected as these galaxies have substantially colder dust temperatures than most literature sources at z>4. We provide direct evidence that, given their cold spectral energy distributions, CMB plays a significant role biasing their observed Rayleigh-Jeans (RJ) slopes to unlikely steep values and, possibly, reducing their CO fluxes by a factor of two. We recover standard RJ slopes when the CMB contribution is taken into account. High resolution ALMA imaging shows compact morphology and evidence for mergers. This work reveals a population of cold dusty star-forming galaxies that were under-represented in current surveys, and are even colder than typical Main Sequence galaxies at the same redshift. The observed cold dust temperatures could be a result of low star formation efficiency with rapid metal enrichment or, more likely, evidence for optically thick dust continuum in the FIR. High FIR dust optical depth might be a widespread feature of compact starbursts at any redshift.

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Section: Introductionmentioning

confidence: 99%

Discovery of Four Apparently Cold Dusty Galaxies at z = 3.62–5.85 in the COSMOS Field: Direct Evidence of Cosmic Microwave Background Impact on High-redshift Galaxy Observables

Jin

Daddi

Magdis

et al. 2019

ApJ

107

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“…Due to the sensitivity and confusion limits (Safarzadeh et al 2015) of current IR surveys, for many UV-selected galaxies, the IR luminosity is unknown; thus, inferring the dust obscuration from the UV slope β is highly desirable if one wishes to constrain the total star formation history of the Universe (e.g., Bouwens et al 2009Bouwens et al , 2012Bouwens et al , 2014Dunlop et al 2012;Finkelstein et al 2012). For galaxies for which M99 relation holds, the observed slope can in principle be used to infer the amount of UV light that has been obscured by dust, and thus one can obtain the intrinsic UV flux and total star formation rate (SFR) from UV observations alone.…”

Section: Introductionmentioning

confidence: 99%

The IRX–β Relation: Insights from Simulations

Safarzadeh

Hayward

Ferguson

2017

ApJ

Self Cite

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We study the relationship between the UV continuum slope and infrared excess ( º L L IRX IR FUV ) predicted by performing dust radiative transfer on a suite of hydrodynamical simulations of galaxies. Our suite includes both isolated disk galaxies and mergers intended to be representative of galaxies at bothz 0 and~-z 2 3. Our lowredshift systems often populate a region around the locally calibrated Meurer et al. relation but move above the relation during merger-induced starbursts. Our high-redshift systems are blue and IR luminous and therefore lie above the Meurer et al. relation. The value of β strongly depends on the dust type used in the RT simulation: Milky-Way-type dust leads to significantly more negative (bluer) slopes compared with Small-Magellanic-Cloudtype dust. The effect on β due to variations in the dust composition with galaxy properties or redshift is the dominant model uncertainty. The dispersion in β is anticorrelated with specific star formation rate (sSFR) and tends to be higher for the~-z 2 3 simulations. In the actively star-forming~-z 2 3 simulated galaxies, dust attenuation dominates the dispersion in β, whereas in thez 0 simulations, the contributions of star formation history (SFH) variations and dust are similar. For low-sSFR systems at both redshifts, SFH variations dominate the dispersion. Finally, the simulated~-z 2 3 isolated disks and mergers both occupy a region in the b -IRX plane consistent with observed~-z 2 3 dusty star-forming galaxies (DSFGs). Thus, contrary to some claims in the literature, the blue colors of high-z DSFGs do not imply that they are short-lived starbursts.

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“…An example of such an area is the development of techniques to extract the maximal amount of information from image pixel data; The UnWISE algorithms and catalogues are examples of the processes that can be used to increase the value of space-based data for an entire survey (Lang, 2014). Similarly, the development of graph and Bayesian techniques have improved the photometry from confused images from the Herschel Space Observatory (Safarzadeh et al, 2015).…”

Section: Algorithm Developmentmentioning

confidence: 99%

LRP2020: Probing Diverse Phenomena through Data-Intensive Astronomy

Rahman,

Lang,

Hložek

et al. 2019

Preprint

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The era of data-intensive astronomy is being ushered in with the increasing size and complexity of observational data across wavelength and time domains, the development of algorithms to extract information from this complexity, and the computational power to apply these algorithms to the growing repositories of data. Data-intensive approaches are pushing the boundaries of nearly all fields of astronomy, from exoplanet science to cosmology, and they are becoming a critical modality for how we understand the universe. The success of these approaches range from the discovery of rare or unexpected phenomena, to characterizing processes that are now accessible with precision astrophysics and a deep statistical understanding of the datasets, to developing algorithms that maximize the science that can be extracted from any set of observations.In this white paper, we propose a number of initiatives to maximize Canada's ability to compete in this data-intensive era. We propose joining international collaborations and leveraging Canadian facilities for legacy data potential. We propose continuing to build a more agile computing infrastructure that's responsive to the needs of tackling larger and more complex data, as well as enabling quick prototyping and scaling of algorithms. We recognize that developing the fundamental skills of the field will be critical for Canadian astronomers, and discuss avenues through with the appropriate computational and statistical training could occur. Finally, we note that the transition to data-intensive techniques is not limited to astronomy, and we should coordinate with other disciplines to develop and make use of best practises in methods, infrastructure, and education.

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A Novel Technique to Improve Photometry in Confused Images Using Graphs and Bayesian Priors

Cited by 19 publications

References 47 publications

Discovery of Four Apparently Cold Dusty Galaxies at z = 3.62–5.85 in the COSMOS Field: Direct Evidence of Cosmic Microwave Background Impact on High-redshift Galaxy Observables

Discovery of Four Apparently Cold Dusty Galaxies at z = 3.62–5.85 in the COSMOS Field: Direct Evidence of Cosmic Microwave Background Impact on High-redshift Galaxy Observables

The IRX–β Relation: Insights from Simulations

LRP2020: Probing Diverse Phenomena through Data-Intensive Astronomy

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