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We present an automated non-parametric light profile extraction pipeline called autoprof. All steps for extracting surface brightness (SB) profiles are included in autoprof , allowing streamlined analyses of galaxy images. autoprof improves upon previous non-parametric ellipse fitting implementations with fit-stabilization procedures adapted from machine learning techniques. Additional advanced analysis methods are included in the flexible pipeline for the extraction of alternative brightness profiles (along radial or axial slices), smooth axisymmetric models, and the implementation of decision trees for arbitrarily complex pipelines. Detailed comparisons with widely used photometry algorithms (photutils, xvista , and galfit) are also presented. These comparisons rely on a large collection of late-type galaxy images from the PROBES catalogue. The direct comparison of SB profiles shows that autoprof can reliably extract fainter isophotes than other methods on the same images, typically by >2 mag arcsec−2. Contrasting non-parametric elliptical isophote fitting with simple parametric models also shows that two-component fits (e.g. Sérsic plus exponential) are insufficient to describe late-type galaxies with high fidelity. It is established that elliptical isophote fitting, and in particular autoprof , is ideally suited for a broad range of automated isophotal analysis tasks. autoprof is freely available to the community at: https://github.com/ConnorStoneAstro/AutoProf. [ABSTRACT FROM AUTHOR]

The aim of this work is to explore the potential of surface brightness fluctuations (SBF) for studying composite stellar populations (CSP). To do so, we have computed the standard (mean) and SBF spectra with E-MILES stellar population synthesis code. We have created a set of models composed by different mass fractions of two single stellar populations, as a first approximation of a CSP scenario. With these models we present an ensemble of SBF colour–colour diagnostic diagrams that reveal different secondary populations depending on the bands used. For this work we focus on those colours capable of unveiling small fractions of metal-poor components in elliptical galaxies, which are dominated by old metal-rich stellar populations. We fit a set of synthetic models and a selection of nearby elliptical galaxies to our CSP models using both mean and SBF colours. We find that the results are highly improved and return small secondary components when mean and SBF values are applied simultaneously, instead of employing them separately or as a constraint. Finally, we explore the possibility of tracking chemical enrichment histories by including in the analysis a variety of SBF colours. For this purpose we present an example where, with two different SBF colour–colour diagrams, we untangle a small contribution of a young solar population and an old metal-poor component from an old solar principal population. The results we have found are promising, but limited by the available data. We highlight the urgent need for new, better, and more consistent SBF observations. [ABSTRACT FROM AUTHOR]

In this study, we demonstrate that stellar masses of galaxies (M star) are universally correlated through a double power-law function with the product of the dynamical velocities (V e) and sizes to one-fourth power (⁠|$R_{\rm e}^{0.25}$|⁠) of galaxies, both measured at the effective radii. The product |$V_{\rm e}R_{\rm e}^{0.25}$| represents the fourth root of the total binding energies within effective radii of galaxies. This stellar mass-binding energy correlation has an observed scatter of 0.14 dex in log(⁠|$V_{\rm e}R_{\rm e}^{0.25}$|⁠) and 0.46 dex in log(M star). It holds for a variety of galaxy types over a stellar mass range of nine orders of magnitude, with little evolution over cosmic time. A toy model of self-regulation between binding energies and supernovae feedback is shown to be able to reproduce the observed slopes, but the underlying physical mechanisms are still unclear. The correlation can be a potential distance estimator with an uncertainty of 0.2 dex independent of the galaxy type. [ABSTRACT FROM AUTHOR]

We monitored the BL Lac object S5 0716+714 in four optical wavebands with four telescopes on 11 nights from 2012 to 2017. The object was active during most of those nights. It was brightest on 2012 November 7 with 11.720 mag in the I band and reached the faintest state on 2016 January 22 with 15.770 mag in the R band corresponding to ∼15.230 mag in the I band. Intraday variations in all bands were found on 6 d, while in partial bands on 3 d. Strong bluer-when-brighter chromatism was observed on 8 nights. Correlation analyses revealed interband time delays from 4 to 40 min in the intraday variability on 5 nights. Both hard and soft lags were observed in this object, indicating complicated emission process in the jet. The analysis on the interband time delays indicated that the radiative cooling may dominate the optical time lags in S5 0716+714 occasionally, but cannot be invoked as the sole explanation. [ABSTRACT FROM AUTHOR]

We present the second part of results of the ongoing project aimed at searching for and studying eXtremely Metal-Poor (XMP) – adopted as those with Z gas ≲ Z⊙/30, or with 12+log (O/H) ≲ 7.21 dex − very gas-rich blue dwarfs in voids. They were first identified in the course of the 'unbiased' study of the galaxy population in the nearby Lynx–Cancer void. These very rare and unusual galaxies seem to be the best proxies of so-called Very Young Galaxies (VYGs) defined recently in model simulations by Tweed et al. To date, for 16 pre-selected void XMP candidates, using the Big Telescope Alt-azimuth (BTA), the SAO 6-m telescope, we have obtained spectra suitable for the determination of O/H. For majority of the observed galaxies, the principal line [O  iii ] λ4363 , used for the direct classical T e method of O/H determination, is undetected. Therefore, to estimate O/H, we use a new 'strong-lines' method by Izotov et al. This appears to be the most accurate empirical O/H estimator for the range of 12+log (O/H) ≲ 7.4–7.5. For objects with higher O/H, we use the semi-empirical method by Izotov & Thuan with our modification accounting for variance of the excitation parameter O 32. Six of those 16 candidates are found, with confidence, to be XMP dwarfs. In addition, eight studied galaxies are less metal-poor, with 12+log (O/H) = 7.24–7.33, and these can also fall into the category of VYG candidates. Taking into account our recently published work and the previously known (nine prototype galaxies) XMP gas-rich void objects, the new findings increase the number of this type of galaxy known to date to a total of 19. [ABSTRACT FROM AUTHOR]

We present the photometric decomposition of spiral galaxies seen at a very large, almost edge-on, angle to the observer. Our sample contains about 150 galaxies of the Sc–Sd morphological types with apparent axis ratios in the B-band. This type of galaxies is of special interest, because their phenomenon is difficult to explain within the modern hierarchical model of galaxy formation. In addition, the galaxies seen at an angle to the observer i ~ 90° allow to study the vertical matter distribution. We used the Pan-STARRS sky survey data in the g-, r-, i-, z-, and y-bands. Our two-component decomposition model included a bulge and a disk. The paper presents the study of this sample including the search for correlations between the parameters obtained during the decomposition, as well as the results of comparing the parameters with the data from the EGIS catalog of visible edge-on galaxies for overlapping objects. [ABSTRACT FROM AUTHOR]

A search for a correlation between the luminosities of the brightest stars and luminosities of their host galaxies was carried out on archival Hubble Space Telescope (HST) or (V) and (I) images of 150 nearby galaxies. The sample contains only galaxies with ongoing star formation and with known distances we derived with the TRGB-method. We correlated the average absolute luminosities of the three brightest blue and the three brightest red stars with the luminosity of a host. We find a linear relation for both the blue and the red stars in irregular and low-mass spiral galaxies. Their scatters are sufficiently small () to make these relations useful for distance determination for low-mass galaxies. We found that all 31 dwarf galaxies in our sample lack bright massive stars , probably due to the physical conditions that prevent their birth. For galaxies with higher an average luminosity in the range , there is an asymmetry in the distribution of the number of galaxies relative to the linear dependence, indicating an increase in the fraction of galaxies with bright stars. [ABSTRACT FROM AUTHOR]

Our recently reported lack of Intra-Night Optical Variability (INOV) among Broad-Absorption-Line (BAL) quasars exhibiting some blazar-like radio properties, either questions polar ejection of BAL clouds, and/or hints at a physical state of the relativistic jet modified due to interaction with the thermal BAL wind on the innermost sub-parsec scale. As a robust check on this unexpected finding for the BAL_blazar candidates, we report here the INOV study of a new and much more rigorously defined comparison sample consisting of 9 normal (non-BAL) blazars, matched in both magnitude and redshift to the aforementioned sample of BAL_blazar candidates. The present campaign spanning 27 sessions yields an INOV duty cycle of ∼23 per cent for the comparison sample of normal blazars, employing the enhanced F-test. However, even this more sensitive test does not detect INOV for the sample of BAL_blazar candidates. This stark INOV contrast found here between the BAL_blazar candidates and normal blazars can probably be traced to a physical interaction of the relativistic jet with the thermal wind, within sub-parsec range from the nucleus. The consequent enfeebling of the jet would additionally explain the striking deficiency among BAL quasars of powerful FR II radio lobes on the much larger scale of 10 – 100 kpc. [ABSTRACT FROM AUTHOR]

To indirectly study the internal structure of giant clumps in main sequence galaxies at z ∼ 1–3, we target very turbulent and gas-rich local analogues from the DYNAMO sample with the Hubble Space Telescope , over a wavelength range of ∼200–480 nm. We present a catalogue of 58 clumps identified in six DYNAMO galaxies, including the WFC3/UVIS F225W, F336W, and F467M photometry where the (225–336) and (336–467) colours are sensitive to extinction and stellar population age, respectively. We measure the internal colour gradients of clumps themselves to study their age and extinction properties. We find a marked colour trend within individual clumps, where the resolved colour distributions show that clumps generally have bluer (336–467) colours (denoting very young ages) in their centres than at their edges, with little variation in the (225–336) colour associated with extinction. Furthermore, we find that clumps whose colours suggest they are older, are preferentially located closer towards the centres of their galaxies, and we find no young clumps at small galactocentric distances. Both results are consistent with simulations of high-redshift star-forming systems that show clumps form via violent disc instability, and through dynamic processes migrate to the centres of their galaxies to contribute to bulge growth on time-scales of a few 100 Myr, while continually forming stars in their centres. When we compare the DYNAMO clumps to those in these simulations, we find the best agreement with the long-lived clumps. [ABSTRACT FROM AUTHOR]

With the dramatic rise in high-quality galaxy data expected from Euclid and Vera C. Rubin Observatory, there will be increasing demand for fast high-precision methods for measuring galaxy fluxes. These will be essential for inferring the redshifts of the galaxies. In this paper, we introduce Lumos , a deep learning method to measure photometry from galaxy images. Lumos builds on BKGnet , an algorithm to predict the background and its associated error, and predicts the background-subtracted flux probability density function. We have developed Lumos for data from the Physics of the Accelerating Universe Survey (PAUS), an imaging survey using a 40 narrow-band filter camera (PAUCam). PAUCam images are affected by scattered light, displaying a background noise pattern that can be predicted and corrected for. On average, Lumos increases the SNR of the observations by a factor of 2 compared to an aperture photometry algorithm. It also incorporates other advantages like robustness towards distorting artefacts, e.g. cosmic rays or scattered light, the ability of deblending and less sensitivity to uncertainties in the galaxy profile parameters used to infer the photometry. Indeed, the number of flagged photometry outlier observations is reduced from 10 to 2 per cent, comparing to aperture photometry. Furthermore, with Lumos photometry, the photo-z scatter is reduced by ≈10 per cent with the Deepz machine-learning photo-z code and the photo-z outlier rate by 20 per cent. The photo-z improvement is lower than expected from the SNR increment, however, currently the photometric calibration and outliers in the photometry seem to be its limiting factor. [ABSTRACT FROM AUTHOR]

Subhalo abundance matching (SHAM) is a popular technique for assigning galaxy mass or luminosity to haloes produced in N -body simulations. The method works by matching the cumulative number functions of the galaxy and halo properties, and is therefore sensitive both to the precise definitions of those properties and to the selection criteria used to define the samples. Further dependence follows when SHAM parameters are calibrated with galaxy clustering, which is known to depend strongly on the manner in which galaxies are selected. In this paper we introduce a new parametrization for SHAM and derive the best-fitting SHAM parameters as a function of various properties of the selection of the galaxy sample and of the photometric definition, including Sérsic versus Petrosian magnitudes, stellar masses versus r -band magnitudes, and optical (Sloan Digital Sky Survey) versus |$\mathrm{H}\, \small {\rm I}$| (ALFALFA) selection. In each case we calculate the models' goodness-of-fit to measurements of the projected two-point galaxy correlation function. In the optically selected samples we find strong evidence that the scatter in the galaxy–halo connection increases towards the faint end, and that AM performs better with luminosity than stellar mass. The SHAM parameters of optically and |$\mathrm{H}\, \small {\rm I}$| -selected galaxies are mutually exclusive, with the latter suggesting the importance of properties beyond halo mass. We provide best-fitting parameters for the SHAM galaxy–halo connection as a function of each of our input choices, extending the domain of validity of the model while reducing potential systematic error in its use. [ABSTRACT FROM AUTHOR]

We report on the stellar content, half-light radii and star formation rates of a sample of 10 known high-redshift (z  ≳ 2) galaxies selected on strong neutral hydrogen (H  i) absorption (⁠|$\log ({\rm N_{H\, \rm {I}}\: /\: cm}^{-2})\,\gt\, 19$|⁠) towards background quasars. We use observations from the Hubble Space Telescope Wide Field Camera 3 in three broad-band filters to study the spectral energy distribution (SED) of the galaxies. Using careful quasar point spread function subtraction, we study their galactic environments, and perform the first systematic morphological characterization of such absorption-selected galaxies at high redshifts. Our analysis reveals complex, irregular hosts with multiple star-forming clumps. At a spatial sampling of 0.067 arcsec per pixel (corresponding to 0.55 kpc at the median redshift of our sample), 40 per cent of our sample requires multiple Sérsic components for an accurate modelling of the observed light distributions. Placed on the mass–size relation and the 'main sequence' of star-forming galaxies, we find that absorption-selected galaxies at high redshift extend known relations determined from deep luminosity-selected surveys to an order of magnitude lower stellar mass, with objects primarily composed of star-forming, late-type galaxies. We measure half-light radii in the range r 1/2 ∼ 0.4 to 2.6 kpc based on the reddest band (F160W) to trace the oldest stellar populations, and stellar masses in the range log (M⋆/M⊙) ∼ 8 to 10 derived from fits to the broad-band SED. Spectroscopic and SED-based star formation rates are broadly consistent, and lie in the range |$\log (\mathrm{SFR}/{\rm M}_{\odot }\, {\rm yr}^{-1}) \sim 0.0$| to 1.7. [ABSTRACT FROM AUTHOR]

We present a detailed analysis of deep far-infrared observations of the nearby edge-on star-forming galaxy NGC 4631 obtained with the Herschel Space Observatory. Our Photodetector Array Camera and Spectrometer (PACS) images at 70 and 160 μm show a rich complex of filaments and chimney-like features that extends up to a projected distance of 6 kpc above the plane of the galaxy. The PACS features often match extraplanar H, radio-continuum, and soft X-ray features observed in this galaxy, pointing to a tight disk-halo connection regulated by star formation. On the other hand, the morphology of the colder dust component detected on a larger scale in the Spectral and Photometric Imaging Receiver 250, 350, and 500 μm data matches the extraplanar H I streams previously reported in NGC 4631 and suggests a tidal origin. The PACS 70/160 μm ratios are elevated in the central ∼3.0 kpc region above the nucleus of this galaxy (the "superbubble"). A pixel-by-pixel analysis shows that dust in this region has a higher temperature and/or an emissivity with a steeper spectral index than the dust in the disk, possibly the result of the harsher environment in the superbubble. Star formation in the disk seems energetically insufficient to lift the material out of the disk, unless it was more active in the past or the dust-to-gas ratio in the superbubble region is higher than the Galactic value. Some of the dust in the halo may also have been tidally stripped from nearby companions or lifted from the disk by galaxy interactions.

We present an extensive catalogue of non-parametric structural properties derived from optical and mid-infrared imaging for 4585 galaxies from the MaNGA survey. DESI and Wide-field Infrared Survey Explorer (WISE) imaging are used to extract surface brightness profiles in the g ,  r ,  z ,  W 1, W 2 photometric bands. Our optical photometry takes advantage of the automated algorithm autoprof and probes surface brightnesses that typically reach below 29 mag arcsec−2 in the r -band, while our WISE photometry achieves 28 mag arcsec−2 in the W 1-band. Neighbour density measures and central/satellite classifications are also provided for a large subsample of the MaNGA galaxies. Highlights of our analysis of galaxy light profiles include (i) an extensive comparison of galaxian structural properties that illustrates the robustness of non-parametric extraction of light profiles over parametric methods; (ii) the ubiquity of bimodal structural properties, suggesting the existence of galaxy families in multiple dimensions; and (iii) an appreciation that structural properties measured relative to total light, regardless of the fractional levels, are uncertain. We study galaxy scaling relations based on photometric parameters, and present detailed comparisons with literature and theory. Salient features of this analysis include the near-constancy of the slope and scatter of the size–luminosity and size–stellar mass relations for late-type galaxies with wavelength, and the saturation of central surface density, measured within 1 kpc, for elliptical galaxies with |$M_* \gt 10.7\, {\rm M}_{\odot }$| (corresponding to |$\Sigma _1 \simeq 10^{10}\, {\rm M}_{\odot }\, {\rm kpc}^{-2}$|⁠). The multiband photometry, environmental parameters, and structural scaling relations presented are useful constraints for stellar population and galaxy formation models. [ABSTRACT FROM AUTHOR]

We present the results of photometric and spectroscopic monitoring campaigns of the changing look AGN NGC 3516 carried out in 2018 to 2020 covering the wavelength range from the X-ray to the optical. The facilities included the telescopes of the CMO SAI MSU, the 2.3-m WIRO telescope, and the XRT and UVOT of Swift. We found that NGC 3516 brightened to a high state and could be classified as Sy1.5 during the late spring of 2020. We have measured time delays in the responses of the Balmer and He  ii λ4686 lines to continuum variations. In the case of the best-characterized broad H β line, the delay to continuum variability is about 17 d in the blue wing and is clearly shorter, 9 d, in the red, which is suggestive of inflow. As the broad lines strengthened, the blue side came to dominate the Balmer lines, resulting in very asymmetric profiles with blueshifted peaks during this high state. During the outburst the X-ray flux reached its maximum on 2020 April 1 and it was the highest value ever observed for NGC 3516 by the Swift observatory. The X-ray hard photon index became softer, ∼1.8 in the maximum on 2020 April 21 compared to the mean ∼0.7 during earlier epochs before 2020. We have found that the UV and optical variations correlated well (with a small time delay of 1–2 d) with the X-ray until the beginning of 2020 April, but later, until the end of 2020 June, these variations were not correlated. We suggest that this fact may be a consequence of partial obscuration by Compton-thick clouds crossing the line of sight. [ABSTRACT FROM AUTHOR]

Spiral structure is ubiquitous in the Universe, and the pitch angle of arms in spiral galaxies provide an important observable in efforts to discriminate between different mechanisms of spiral arm formation and evolution. In this paper, we present a hierarchical Bayesian approach to galaxy pitch angle determination, using spiral arm data obtained through the Galaxy Builder citizen science project. We present a new approach to deal with the large variations in pitch angle between different arms in a single galaxy, which obtains full posterior distributions on parameters. We make use of our pitch angles to examine previously reported links between bulge and bar strength and pitch angle, finding no correlation in our data (with a caveat that we use observational proxies for both bulge size and bar strength which differ from other work). We test a recent model for spiral arm winding, which predicts uniformity of the cotangent of pitch angle between some unknown upper and lower limits, finding our observations are consistent with this model of transient and recurrent spiral pitch angle as long as the pitch angle at which most winding spirals dissipate or disappear is larger than 10°. [ABSTRACT FROM AUTHOR]

A detailed study of the morphology of lenticular galaxies is an important way to understand how this type of galaxy is formed and evolves over time. Decomposing a galaxy into its components (disc, bulge, bar,...) allows recovering the colour gradients present in each system, its star formation history, and its assembly history. We use galfitm to perform a multiwavelength structural decomposition of the closest lenticular galaxy, NGC 3115, resulting in the description of its stellar light into several main components: a bulge, a thin disc, a thick disc, and also evidence of a bar. We report the finding of central bluer stellar populations in the bulge, as compared to the colour of the galaxy outskirts, indicating either the presence of an active galactic nucleus (AGN) and/or recent star formation activity. From the spectral energy distribution results, we show that the galaxy has a low luminosity AGN component, but even excluding the effect of the nuclear activity, the bulge is still bluer than the outer-regions of the galaxy, revealing a recent episode of star formation. Based on all of the derived properties, we propose a scenario for the formation of NGC 3115 consisting of an initial gas-rich merger, followed by accretions and feedback that quench the galaxy, until a recent encounter with the companion KK084 that reignited the star formation in the bulge, provoked a core displacement in NGC 3115 and generated spiral-like features. This result is consistent with the two-phase formation scenario, proposed in previous studies of this galaxy. [ABSTRACT FROM AUTHOR]

We use near-infrared (J − K) colours of bright 2MASS galaxies, measured within a  7- arcsec-radius aperture, to calibrate the Schlegel, Finkbeiner & Davis DIRBE/IRAS Galactic extinction map at low Galactic latitudes (| b | < 10°). Using 3460 galaxies covering a large range in extinction (up to A K |$=1{_{.}^{\rm m}}15$| or E (B − V) |$\simeq 3{_{.}^{\rm m}}19$|⁠), we derive a correction factor f  = 0.83 ± 0.01 by fitting a linear regression to the colour-extinction relation, confirming that the Schlegel et al. maps overestimate the extinction. We argue that the use of only a small range in extinction (e.g. A K |$\lt 0{_{.}^{\rm m}}4$|⁠) increases the uncertainty in the correction factor and may overestimate it. Our data confirm the Fitzpatrick extinction law for the J- and K -band. We also tested four all-sky extinction maps based on Planck satellite data. All maps require a correction factor as well. In three cases, the application of the respective extinction correction to the galaxy colours results in a reduced scatter in the colour-extinction relation, indicating a more reliable extinction correction. Finally, the large galaxy sample allows an analysis of the calibration of the extinction maps as a function of Galactic longitude and latitude. For all but one extinction map, we find a marked offset between the Galactic Centre and Anticentre region, but not with the dipole of the cosmic microwave background. Based on our analysis, we recommend the use of the GNILC extinction map by Planck Collaboration XLVIII with a correction factor f  = 0.86 ± 0.01. [ABSTRACT FROM AUTHOR]

Using deep narrow-band (NB) imaging and optical spectroscopy from the Keck telescope and MMT, we identify a sample of 20 emission-line galaxies at z = 0.065-0.90 where the weak auroral emission line, [O III] λ4363, is detected at ≥3σ. These detections allow us to determine the gas-phase metallicity using the "direct" method. With electron temperature measurements, and dust attenuation corrections from Balmer decrements, we find that four of these low-mass galaxies are extremely metal-poor with 12 + log (O/H) ≤ 7.65 or one-tenth solar. Our most metal-deficient galaxy has 12 + log (O/H) = 7.24 (95% confidence), similar to some of the lowest metallicity galaxies identified in the local universe. We find that our galaxies are all undergoing significant star formation with average specific star formation rate (SFR) of (100 Myr)-1, and that they have high central SFR surface densities (average of 0.5 M yr-1 kpc-2). In addition, more than two-thirds of our galaxies have between one and four nearby companions within a projected radius of 100 kpc, which we find is an excess among star-forming galaxies at z = 0.4-0.85. We also find that the gas-phase metallicities for a given stellar mass and SFR lie systematically lower than the local M-Z-(SFR) relation by 0.2 dex (2σ significance). These results are partly due to selection effects, since galaxies with strong star formation and low metallicity are more likely to yield [O III] λ4363 detections. Finally, the observed higher ionization parameter and high electron density suggest that they are lower redshift analogs to typical z ≳ 1 galaxies. © 2014. The American Astronomical Society. All rights reserved..

Hundreds of Type 2 quasars have been identified in Sloan Digital Sky Survey (SDSS) data, and there is substantial evidence that they are generally galaxies with highly obscured central engines, in accord with unified models for active galactic nuclei (AGNs). A straightforward expectation of unified models is that highly obscured Type 2 AGNs should show little or no optical variability on timescales of days to years. As a test of this prediction, we have carried out a search for variability in Type 2 quasars in SDSS Stripe 82 using difference-imaging photometry. Starting with the Type 2 AGN catalogs of Zakamska et al. and Reyes et al., we find evidence of significant g-band variability in 17 out of 173 objects for which light curves could be measured from the Stripe 82 data. To determine the nature of this variability, we obtained new Keck spectropolarimetry observations for seven of these variable AGNs. The Keck data show that these objects have low continuum polarizations (p ≲ 1% in most cases) and all seven have broad Hα and/or Mg II emission lines in their total (unpolarized) spectra, indicating that they should actually be classified as Type 1 AGNs. We conclude that the primary reason variability is found in the SDSS-selected Type 2 AGN samples is that these samples contain a small fraction of Type 1 AGNs as contaminants, and it is not necessary to invoke more exotic possible explanations such as a population of "naked" or unobscured Type 2 quasars. Aside from misclassified Type 1 objects, the Type 2 quasars do not generally show detectable optical variability over the duration of the Stripe 82 survey. © 2014. The American Astronomical Society. All rights reserved..

We implement a linear model for mitigating the effect of observing conditions and other sources of contamination in galaxy clustering analyses. Our treatment improves upon the fiducial systematics treatment of the Dark Energy Survey (DES) Year 1 (Y1) cosmology analysis in four crucial ways. Specifically, our treatment (1) does not require decisions as to which observable systematics are significant and which are not, allowing for the possibility of multiple maps adding coherently to give rise to significant bias even if no single map leads to a significant bias by itself, (2) characterizes both the statistical and systematic uncertainty in our mitigation procedure, allowing us to propagate said uncertainties into the reported cosmological constraints, (3) explicitly exploits the full spatial structure of the galaxy density field to differentiate between cosmology-sourced and systematics-sourced fluctuations within the galaxy density field, and (4) is fully automated, and can therefore be trivially applied to any data set. The updated correlation function for the DES Y1 redMaGiC catalogue minimally impacts the cosmological posteriors from that analysis. Encouragingly, our analysis does improve the goodness-of-fit statistic of the DES Y1 3 × 2pt data set (Δχ2 = −6.5 with no additional parameters). This improvement is due in nearly equal parts to both the change in the correlation function and the added statistical and systematic uncertainties associated with our method. We expect the difference in mitigation techniques to become more important in future work as the size of cosmological data sets grows. [ABSTRACT FROM AUTHOR]

We present a comprehensive study of an unbiased sample of 150 nearby (median redshift, z = 0.014) core-collapse supernova (CCSN) host galaxies drawn from the All-Sky Automated Survey for Supernovae (ASAS-SN) for direct comparison to the nearest long-duration gamma-ray burst (LGRB) and superluminous supernova (SLSN) hosts. We use public imaging surveys to gather multiwavelength photometry for all CCSN host galaxies and fit their spectral energy distributions (SEDs) to derive stellar masses and integrated star formation rates (SFRs). CCSNe populate galaxies across a wide range of stellar masses, from blue and compact dwarf galaxies to large spiral galaxies. We find 33 |$^{+4}_{-4}$| per cent of CCSNe are in dwarf galaxies (M * < 109 M⊙) and 2 |$^{+2}_{-1}$| per cent are in dwarf starburst galaxies [specific star formation rate (sSFR) > 10−8 yr−1]. We reanalyse low-redshift SLSN and LGRB hosts from the literature (out to z < 0.3) in a homogeneous way and compare against the CCSN host sample. The relative SLSN to CCSN supernova rate is increased in low-mass galaxies and at high sSFRs. These parameters are strongly covariant and we cannot break the degeneracy between them with our current sample, although there is some evidence that both factors may play a role. Larger unbiased samples of CCSNe from projects such as ZTF and LSST will be needed to determine whether host-galaxy mass (a proxy for metallicity) or sSFR (a proxy for star formation intensity and potential IMF variation) is more fundamental in driving the preference for SLSNe and LGRBs in unusual galaxy environments. [ABSTRACT FROM AUTHOR]

The scientific value of the next generation of large continuum surveys would be greatly increased if the redshifts of the newly detected sources could be rapidly and reliably estimated. Given the observational expense of obtaining spectroscopic redshifts for the large number of new detections expected, there has been substantial recent work on using machine learning techniques to obtain photometric redshifts. Here, we compare the accuracy of the predicted photometric redshifts obtained from deep learning (DL) with the k- nearest neighbour (kNN) and the decision tree regression (DTR) algorithms. We find using a combination of near-infrared, visible, and ultraviolet magnitudes, trained upon a sample of Sloan Digital Sky Survey quasi-stellar objects, that the kNN and DL algorithms produce the best self-validation result with a standard deviation of σΔ z = 0.24 (σΔ z (norm) = 0.11). Testing on various subsamples, we find that the DL algorithm generally has lower values of σΔ z , in addition to exhibiting a better performance in other measures. Our DL method, which uses an easy to implement off-the-shelf algorithm with neither filtering nor removal of outliers, performs similarly to other, more complex, algorithms, resulting in an accuracy of Δ z < 0.1 up to z ∼ 2.5. Applying the DL algorithm trained on our 70 000 strong sample to other independent (radio-selected) data sets, we find σΔ z ≤ 0.36 (σΔ z (norm) ≤ 0.17) over a wide range of radio flux densities. This indicates much potential in using this method to determine photometric redshifts of quasars detected with the Square Kilometre Array. [ABSTRACT FROM AUTHOR]

We present 'Pix2Prof', a deep learning model that can eliminate any manual steps taken when measuring galaxy profiles. We argue that a galaxy profile of any sort is conceptually similar to a natural language image caption. This idea allows us to leverage image captioning methods from the field of natural language processing, and so we design Pix2Prof as a float sequence 'captioning' model suitable for galaxy profile inference. We demonstrate the technique by approximating a galaxy surface brightness (SB) profile fitting method that contains several manual steps. Pix2Prof processes ∼1 image per second on an Intel Xeon E5-2650 v3 CPU, improving on the speed of the manual interactive method by more than two orders of magnitude. Crucially, Pix2Prof requires no manual interaction, and since galaxy profile estimation is an embarrassingly parallel problem, we can further increase the throughput by running many Pix2Prof instances simultaneously. In perspective, Pix2Prof would take under an hour to infer profiles for 105 galaxies on a single NVIDIA DGX-2 system. A single human expert would take approximately 2 yr to complete the same task. Automated methodology such as this will accelerate the analysis of the next generation of large area sky surveys expected to yield hundreds of millions of targets. In such instances, all manual approaches – even those involving a large number of experts – will be impractical. [ABSTRACT FROM AUTHOR]

The Solo (So litary Lo cal) Dwarf Galaxy survey is a volume-limited, wide-field g - and i -band survey of all known nearby (<3 Mpc) and isolated (>300 kpc from the Milky Way or M31) dwarf galaxies. This set of 44 dwarfs is homogeneously analysed for quantitative comparisons to the satellite dwarf populations of the Milky Way and M31. In this paper, an analysis of the 12 closest Solo dwarf galaxies accessible from the Northern hemisphere is presented, including derivation of their distances, spatial distributions, morphology, and extended structures, including their inner integrated light properties and their outer resolved star distributions. All 12 galaxies are found to be reasonably well described by two-dimensional Sérsic functions, although UGC 4879 in particular shows tentative evidence of two distinct components. No prominent extended stellar substructures, which could be signs of either faint satellites or recent mergers, are identified in the outer regions of any of the systems examined. [ABSTRACT FROM AUTHOR]

The dominant physical formation mechanism(s) for ultradiffuse galaxies (UDGs) is still poorly understood. Here, we combine new, deep imaging from the Jeanne Rich Telescope with deep integral field spectroscopy from the Keck II telescope to investigate the formation of UDG1137+16 (dw1137+16). Our new analyses confirm both its environmental association with the low density UGC 6594 group, along with its large size of 3.3 kpc and status as a UDG. The new imaging reveals two distinct stellar components for UDG1137+16, indicating that a central stellar body is surrounded by an outer stellar envelope undergoing tidal interaction. Both the components have approximately similar stellar masses. From our integral field spectroscopy, we measure a stellar velocity dispersion within the half-light radius (15 ± 4 km s−1) and find that UDG1137+16 is similar to some other UDGs in that it is likely dark matter dominated. Incorporating literature measurements, we also examine the current state of UDG observational kinematics. Placing these data on the central stellar velocity dispersion–stellar mass relation, we suggest there is little evidence for UDG1137+16 being created through a strong tidal interaction. Finally, we investigate the constraining power current dynamical mass estimates (from stellar and globular cluster velocity dispersions) have on the total halo mass of UDGs. As most are measured within the half-light radius, they are unable to accurately constrain UDG total halo masses. [ABSTRACT FROM AUTHOR]

Understanding the geometry and kinematics of the broad line region (BLR) of active galactic nuclei (AGN) is important to estimate black hole masses in AGN and study the accretion process. The technique of reverberation mapping (RM) has provided estimates of BLR size for more than 100 AGN now; however, the structure of the BLR has been studied for only a handful number of objects. Towards this, we investigated the geometry of the BLR for a large sample of 57 AGN using archival RM data. We performed systematic modelling of the continuum and emission line light curves using a Markov chain Monte Carlo method based on Bayesian statistics implemented in PBMAP (Parallel Bayesian code for reverberation−MAPping data) code to constrain BLR geometrical parameters and recover velocity integrated transfer function. We found that the recovered transfer functions have various shapes such as single-peaked, double-peaked, and top-hat suggesting that AGN have very different BLR geometries. Our model lags are in general consistent with that estimated using the conventional cross-correlation methods. The BLR sizes obtained from our modelling approach is related to the luminosity with a slope of 0.583 ± 0.026 and 0.471 ± 0.084 based on H β and H α lines, respectively. We found a non-linear response of emission line fluxes to the ionizing optical continuum for 93 |${{\ \rm per\ cent}}$| objects. The estimated virial factors for the AGN studied in this work range from 0.79 to 4.94 having a mean at 1.78 ± 1.77 consistent with the values found in the literature. [ABSTRACT FROM AUTHOR]

We present – and make publicly available – accurate and precise photometric redshifts in the ACS footprint from the COSMOS field for objects with i AB ≤ 23. The redshifts are computed using a combination of narrow-band photometry from PAUS, a survey with 40 narrow bands spaced at |$100\,\mathring{\rm A}$| intervals covering the range from 4500 to |$8500\,\mathring{\rm A}$|⁠ , and 26 broad, intermediate, and narrow bands covering the UV, visible and near-infrared spectrum from the COSMOS2015 catalogue. We introduce a new method that models the spectral energy distributions as a linear combination of continuum and emission-line templates and computes its Bayes evidence, integrating over the linear combinations. The correlation between the UV luminosity and the O  ii line is measured using the 66 available bands with the zCOSMOS spectroscopic sample, and used as a prior which constrains the relative flux between continuum and emission-line templates. The flux ratios between the O  ii line and H α , H β and |$\mathrm{O\,{\small III}}$| are similarly measured and used to generate the emission-line templates. Comparing to public spectroscopic surveys via the quantity Δ z ≡ (z photo − z spec)/(1 + z spec), we find the photometric redshifts to be more precise than previous estimates, with σ 68(Δ z ) ≈ (0.003, 0.009) for galaxies at magnitude i AB ∼ 18 and i AB ∼ 23, respectively, which is three times and 1.66 times tighter than COSMOS2015. Additionally, we find the redshifts to be very accurate on average, yielding a median of the Δ z distribution compatible with |median(Δ z )| ≤ 0.001 at all redshifts and magnitudes considered. Both the added PAUS data and new methodology contribute significantly to the improved results. The catalogue produced with the technique presented here is expected to provide a robust redshift calibration for current and future lensing surveys, and allows one to probe galaxy formation physics in an unexplored luminosity-redshift regime, thanks to its combination of depth, completeness, and excellent redshift precision and accuracy. [ABSTRACT FROM AUTHOR]

We present the photometric properties of galaxies in the First Light And Reionization Epoch Simulations (FLARES). The simulations trace the evolution of galaxies in a range of overdensities through the epoch of reionization. With a novel weighting scheme, we combine these overdensities, extending significantly the dynamic range of observed composite distribution functions compared to periodic simulation boxes. FLARES predicts a significantly larger number of intrinsically bright galaxies, which can be explained through a simple model linking dust attenuation to the metal content of the interstellar medium, using a line-of-sight extinction model. With this model, we present the photometric properties of the FLARES galaxies for z ∈ [5, 10]. We show that the ultraviolet (UV) luminosity function (LF) matches the observations at all redshifts. The function is fitted by Schechter and double power-law forms, with the latter being favoured at these redshifts by the FLARES composite UV LF. We also present predictions for the UV-continuum slope as well as the attenuation in the UV. The impact of environment on the UV LF is also explored, with the brightest galaxies forming in the densest environments. We then present the line luminosity and equivalent widths of some prominent nebular emission lines arising from the galaxies, finding rough agreement with available observations. We also look at the relative contribution of obscured and unobscured star formation, finding comparable contributions at these redshifts. [ABSTRACT FROM AUTHOR]

We present an updated and revised analysis of the relationship between the Hβ broad-line region (BLR) radius and the luminosity of the active galactic nucleus (AGN). Specifically, we have carried out two-dimensional surface brightness decompositions of the host galaxies of nine new AGNs imaged with the Hubble Space Telescope Wide Field Camera 3. The surface brightness decompositions allow us to create "AGN-free" images of the galaxies, from which we measure the starlight contribution to the optical luminosity measured through the ground-based spectroscopic aperture. We also incorporate 20 new reverberation-mapping measurements of the Hβ time lag, which is assumed to yield the average Hβ BLR radius. The final sample includes 41 AGNs covering four orders of magnitude in luminosity. The additions and updates incorporated here primarily affect the low-luminosity end of the R BLR-L relationship. The best fit to the relationship using a Bayesian analysis finds a slope of , consistent with previous work and with simple photoionization arguments. Only two AGNs appear to be outliers from the relationship, but both of them have monitoring light curves that raise doubt regarding the accuracy of their reported time lags. The scatter around the relationship is found to be 0.19 ± 0.02 dex, but would be decreased to 0.13 dex by the removal of these two suspect measurements. A large fraction of the remaining scatter in the relationship is likely due to the inaccurate distances to the AGN host galaxies. Our results help support the possibility that the RBLR-L relationship could potentially be used to turn the BLRs of AGNs into standardizable candles. This would allow the cosmological expansion of the universe to be probed by a separate population of objects, and over a larger range of redshifts. © 2013. The American Astronomical Society. All rights reserved.

We present new measurements of the very low mass end of the galaxy stellar mass function (GSMF) at z  ∼ 6−7 computed from a rest-frame ultraviolet selected sample of dropout galaxies. These galaxies lie behind the six Hubble Frontier Field clusters and are all gravitationally magnified. Using deep Spitzer /IRAC and Hubble Space Telescope imaging, we derive stellar masses by fitting galaxy spectral energy distributions and explore the impact of different model assumptions and parameter degeneracies on the resulting GSMF. Our sample probes stellar masses down to |$M_{\star }\gt 10^{6}\, \text{M}_{\odot}$| and we find the z  ∼ 6−7 GSMF to be best parametrized by a modified Schechter function that allows for a turnover at very low masses. Using a Monte Carlo Markov chain analysis of the GSMF, including accurate treatment of lensing uncertainties, we obtain a relatively steep low-mass end slope |$\alpha \simeq -1.96_{-0.08}^{+0.09}$| and a turnover at |$\log (M_T/\text{M}_{\odot})\simeq 7.10_{-0.56}^{+0.17}$| with a curvature of |$\beta \simeq 1.00_{-0.73}^{+0.87}$| for our minimum assumption model with constant star formation history (SFH) and low dust attenuation, AV  ≤ 0.2. We find that the z  ∼ 6−7 GSMF, in particular its very low mass end, is significantly affected by the assumed functional form of the star formation history and the degeneracy between stellar mass and dust attenuation. For example, the low-mass end slope ranges from |$\alpha \simeq -1.82_{-0.07}^{+0.08}$| for an exponentially rising SFH to |$\alpha \simeq -2.34_{-0.10}^{+0.11}$| when allowing AV of up to 3.25. Future observations at longer wavelengths and higher angular resolution with the James Webb Space Telescope are required to break these degeneracies and to robustly constrain the stellar mass of galaxies on the extreme low-mass end of the GSMF. [ABSTRACT FROM AUTHOR]

We explore the relation between diffuse intracluster light (central galaxy included) and the galaxy cluster (baryonic and dark) matter distribution using a sample of 528 clusters at 0.2 ≤ z ≤ 0.35 found in the Dark Energy Survey (DES) Year 1 data. The surface brightness of the diffuse light shows an increasing dependence on cluster total mass at larger radius, and appears to be self-similar with a universal radial dependence after scaling by cluster radius. We also compare the diffuse light radial profiles to the cluster (baryonic and dark) matter distribution measured through weak lensing and find them to be comparable. The IllustrisTNG galaxy formation simulation, TNG300, offers further insight into the connection between diffuse stellar mass and cluster matter distributions – the simulation radial profile of the diffuse stellar component does not have a similar slope with the total cluster matter content, although that of the cluster satellite galaxies does. Regardless of the radial trends, the amount of diffuse stellar mass has a low-scatter scaling relation with cluster's total mass in the simulation, out-performing the total stellar mass of cluster satellite galaxies. We conclude that there is no consistent evidence yet on whether or not diffuse light is a faithful radial tracer of the cluster matter distribution. Nevertheless, both observational and simulation results reveal that diffuse light is an excellent indicator of the cluster's total mass. [ABSTRACT FROM AUTHOR]

We present correlations involving central intensity ratio (CIR) of 52 early-type galaxies, including 24 ellipticals and 28 lenticulars, selected from low-density environment in the nearby (<30 Mpc) universe. CIR is found to be negatively and significantly correlated with the mass of the central supermassive black hole, central velocity dispersion, absolute B -band magnitude, stellar bulge mass, and central Mg2 index of the host galaxy. The study proposes the use of CIR as a simple, fast, and efficient photometric tool for exploring the co-evolution scenario existing in galaxies. [ABSTRACT FROM AUTHOR]

We present a study of the 1173 sources brighter than |$S_{1.4\, \rm GHz}= 120\, \mu$| Jy detected over an area of |$\simeq 1.4\, \hbox{deg}^{2}$| in the Lockman Hole field. Exploiting the multiband information available in this field for ∼79 per cent of the sample, sources have been classified into radio loud (RL) active galactic nuclei (AGNs), star-forming galaxies (SFGs), and radio quiet (RQ) AGNs, using a variety of diagnostics available in the literature. Exploiting the observed tight anticorrelations between IRAC band 1 or band 2 and the source redshift we could assign a redshift to 177 sources missing a spectroscopic measurement or a reliable photometric estimate. A Monte Carlo approach was used to take into account the spread around the mean relation. The derived differential number counts and luminosity functions at several redshifts of each population show a good consistency with models and with earlier estimates made using data from different surveys and applying different approaches. Our results confirm that below |$\sim 300\, \mu$| Jy SFGs+RQ AGNs overtake RL AGNs that dominate at brighter flux densities. We also confirm earlier indications of a similar evolution of RQ AGNs and SFGs. Finally, we discuss the angular correlation function of our sources and highlight its sensitivity to the criteria used for the classification. [ABSTRACT FROM AUTHOR]

Theoretical models suggest that galaxy mergers may have profoundly shaped galaxy morphologies through cosmic time. However, observational estimates of galaxy pair fractions, and implied galaxy mergers, still do not converge, suggesting different numbers and redshift evolution. This paper explores the connection between stellar mass estimation and the pair fraction of galaxies using |$\rm {\small STEEL}$|⁠ , the Statistical sEmi-Emprical modeL, in which galaxies are mapped on to host dark matter haloes via a stellar mass–halo mass (SMHM) relation. As haloes of different mass are predicted to undergo, on average, different degrees of mergers, we expect that galaxy merger rates at fixed stellar mass will also vary depending on the shape of the input SMHM relation. Using a variety of input SMHM relations, also including one that matches the outputs of the Illustris TNG simulation, we thoroughly explore how systematic variations in the stellar mass functions propagate on to the normalization and redshift dependence of the galaxy pair fraction. We find that (i) stellar mass functions characterized by larger number densities of massive galaxies and thus a steeper SMHM relation, result in a substantial reduction of the pair fractions of massive galaxies; (ii) a time-varying SMHM relation produces galaxy pair fractions that can have varied redshift evolutions. We argue that in a hierarchical, dark matter dominated Universe, stellar mass estimates are a considerable cause of bias that must be accounted for when comparing pair fractions from different data sets or from theoretical models developed independently of the fitted survey data. [ABSTRACT FROM AUTHOR]

We present the first detailed study of the stellar populations of star-forming galaxies at z ∼ 1.5, which are selected by their [O II] emission line, detected in narrowband surveys. We identified ∼1300 [O II] emitters at z = 1.47 and z = 1.62 in the Subaru Deep Field with rest-frame equivalent widths (EWs) above 13 Å. Optical and near-infrared spectroscopic observations for ≈10% of our samples show that our separation of [O II] from [O III] emission-line galaxies in two-color space is 99% successful. We analyze the multi-wavelength properties of a subset of ∼1200 galaxies with the best photometry. They have average rest-frame EW of 45 Å, stellar mass of 3 × 109 M⊙, and stellar age of 100Myr. In addition, our spectral energy distribution (SED) fitting and broadband colors indicate that [O II] emitters span the full range of galaxy populations at z ∼ 1.5. We also find that 80% of [O II] emitters are also photometrically classified as "BX/BM" (UV) galaxies and/or the star-forming "BzK" (near-IR) galaxies. Our [O II] emission line survey produces a far more complete and somewhat deeper sample of z ∼ 1.5 galaxies than either the BX/BM or sBzK selection alone. We constructed average SEDs and find that higher [O II] EW galaxies have somewhat bluer continua. SED model-fitting shows that they have on average half the stellar mass of galaxies with lower [O II] EW. The observed [O II] luminosity is well correlated with the far-UV continuum with a logarithmic slope of 0.89 ± 0.22. The scatter of the [O II] luminosity against the far-UV continuum suggests that [O II] can be used as a star formation rate indicator with a reliability of 0.23 dex. © 2012. The American Astronomical Society. All rights reserved.

We present the first detailed study of the stellar populations of star-forming galaxies at z ∼ 1.5, which are selected by their [O II] emission line, detected in narrowband surveys. We identified ∼1300 [O II] emitters at z = 1.47 and z = 1.62 in the Subaru Deep Field with rest-frame equivalent widths (EWs) above 13 Å. Optical and near-infrared spectroscopic observations for ≈10% of our samples show that our separation of [O II] from [O III] emission-line galaxies in two-color space is 99% successful. We analyze the multi-wavelength properties of a subset of ∼1200 galaxies with the best photometry. They have average rest-frame EW of 45 Å, stellar mass of 3 × 109 M⊙, and stellar age of 100Myr. In addition, our spectral energy distribution (SED) fitting and broadband colors indicate that [O II] emitters span the full range of galaxy populations at z ∼ 1.5. We also find that 80% of [O II] emitters are also photometrically classified as "BX/BM" (UV) galaxies and/or the star-forming "BzK" (near-IR) galaxies. Our [O II] emission line survey produces a far more complete and somewhat deeper sample of z ∼ 1.5 galaxies than either the BX/BM or sBzK selection alone. We constructed average SEDs and find that higher [O II] EW galaxies have somewhat bluer continua. SED model-fitting shows that they have on average half the stellar mass of galaxies with lower [O II] EW. The observed [O II] luminosity is well correlated with the far-UV continuum with a logarithmic slope of 0.89 ± 0.22. The scatter of the [O II] luminosity against the far-UV continuum suggests that [O II] can be used as a star formation rate indicator with a reliability of 0.23 dex. © 2012. The American Astronomical Society. All rights reserved.

Using deep narrowband and broadband imaging, we identify 401 z ≈ 0.40 and 249 z ≈ 0.49 Hαline-emitting galaxies in the Subaru Deep Field. Compared to other Hαsurveys at similar redshifts, our samples are unique since they probe lower Hαluminosities, are augmented with multi-wavelength (rest-frame 1000 -1.5 μm) coverage, and a large fraction (20%) of our samples has already been spectroscopically confirmed. Our spectra allow us to measure the Balmer decrement for nearly 60 galaxies with Hβ detected above 5σ. The Balmer decrements indicate an average extinction of A(Hα) = 0.7+1.4-0.7mag. We find that the Balmer decrement systematically increases with higher Hαluminosities and with larger stellar masses, in agreement with previous studies with sparser samples. We find that the star formation rates (SFRs) estimated from modeling the spectral energy distribution (SED) are reliable - we derived an "intrinsic" Hαluminosity which is then reddened assuming the color excess from SED modeling. The SED-predicted Hαluminosity agrees with Hαnarrowband measurements over 3dex (rms of 0.25dex). We then use the SED SFRs to test different statistically based dust corrections for Hαand find that adopting 1mag of extinction is inappropriate: galaxies with lower luminosities are less reddened. We find that the luminosity-dependent dust correction of Hopkins et al. yields consistent results over 3dex (rms of 0.3dex). Our comparisons are only possible by assuming that stellar reddening is roughly half of nebular reddening. The strong correspondence argues that with SED modeling, we can derive reliable intrinsic SFRs even in the absence of Hαmeasurements at z ∼ 0.5. © 2012. The American Astronomical Society. All rights reserved.

Using deep narrowband and broadband imaging, we identify 401 z ≈ 0.40 and 249 z ≈ 0.49 Hαline-emitting galaxies in the Subaru Deep Field. Compared to other Hαsurveys at similar redshifts, our samples are unique since they probe lower Hαluminosities, are augmented with multi-wavelength (rest-frame 1000 -1.5 μm) coverage, and a large fraction (20%) of our samples has already been spectroscopically confirmed. Our spectra allow us to measure the Balmer decrement for nearly 60 galaxies with Hβ detected above 5σ. The Balmer decrements indicate an average extinction of A(Hα) = 0.7+1.4-0.7mag. We find that the Balmer decrement systematically increases with higher Hαluminosities and with larger stellar masses, in agreement with previous studies with sparser samples. We find that the star formation rates (SFRs) estimated from modeling the spectral energy distribution (SED) are reliable - we derived an "intrinsic" Hαluminosity which is then reddened assuming the color excess from SED modeling. The SED-predicted Hαluminosity agrees with Hαnarrowband measurements over 3dex (rms of 0.25dex). We then use the SED SFRs to test different statistically based dust corrections for Hαand find that adopting 1mag of extinction is inappropriate: galaxies with lower luminosities are less reddened. We find that the luminosity-dependent dust correction of Hopkins et al. yields consistent results over 3dex (rms of 0.3dex). Our comparisons are only possible by assuming that stellar reddening is roughly half of nebular reddening. The strong correspondence argues that with SED modeling, we can derive reliable intrinsic SFRs even in the absence of Hαmeasurements at z ∼ 0.5. © 2012. The American Astronomical Society. All rights reserved.

Several UV and near-infrared color selection methods have identified galaxies at z = 1-3. Since each method suffers from selection biases, we have simultaneously applied three leading techniques (Lyman break, BX/BM, and BzK selection) in the Subaru Deep Field. This field has reliable (Δz/(1 + z) = 0.02-0.09) photometric redshifts for 53,000 galaxies from 20 bands (1500 -2.2 μm). The BzK, LBG, and BX/BM samples suffer contamination from z < 1 interlopers of 6%, 8%, and 20%, respectively. Around the redshifts where it is most sensitive (z 1.9 for star-forming BzK, z 1.8 for z 2 LBGs, z 1.6 for BM, and z 2.3 for BX), each technique finds 60%-80% of the census of the three methods. In addition, each of the color techniques shares 75%-96% of its galaxies with another method, which is consistent with previous studies that adopt identical criteria on magnitudes and colors. Combining the three samples gives a comprehensive census that includes 90% of z phot = 1-3 galaxies, using standard magnitude limits similar to previous studies. In fact, we find that among z = 1-2.5 galaxies in the color selection census, 81%-90% of them can be selected by just combining the BzK selection with one of the UV techniques (z 2 LBG or BX and BM). The average galaxy stellar mass, reddening, and star formation rates (SFRs) all decrease systematically from the sBzK population to the LBGs, and to the BX/BMs. The combined color selections yield a total cosmic SFR density of 0.18 0.03 M yr-1 Mpc-3 for K AB ≲ 24. We find that 65% of the star formation is in galaxies with E(B - V) > 0.25mag, even though they are only one-fourth of the census by number. © 2011. The American Astronomical Society. All rights reserved..

Recent orbital studies of 3D bar structure in various numerical and analytical models show that X-structures that reside in boxy/peanut-shaped (B/PS) bulges are not delineated by some specific type of orbits, but are natural parts of them and formed by the same orbits that constitute such bulges. This implies that to accurately account for B/PS bulges and their X-structures in photometric studies, one needs the photometric model of B/PS bulge that includes an X-structure as its natural part. To find such a model, we considered a self-consistent numerical galaxy model where a typical B/PS bulge arises. Using spectral characteristics of particle-'stars', we decomposed the galaxy model on to the bar and non-bar components. We used the extracted 3D bar component to find an appropriate B/PS bulge photometric model, which can account for X-structures residing in such bulges. The resulted B/PS bulge photometric model has a truncated 2D Sersic profile with truncations introduced above (in the upper half-plane) and below (in the bottom half-plane) the rays of X-structures. We applied this model to represent B/PS bulges of various numerical models and some real galaxies. The comparison with previous works revealed that there are systematic shifts between the X-structure parameters of the same galaxies measured within the different approaches. We found that the geometric parameters of X-structures of real and modelled galaxies are consistent with each other if we measure them using our new model. [ABSTRACT FROM AUTHOR]

We present a map of the total intrinsic reddening across ≃34 deg2 of the Small Magellanic Cloud (SMC) derived using optical (ugriz) and near-infrared (IR; YJK s) spectral energy distributions (SEDs) of background galaxies. The reddening map is created using a subsample of 29 274 galaxies with low levels of intrinsic reddening based on the lephare χ2 minimization SED-fitting routine. We find statistically significant enhanced levels of reddening associated with the main body of the SMC compared with regions in the outskirts [Δ E (B − V) ≃ 0.3 mag]. A comparison with literature reddening maps of the SMC shows that, after correcting for differences in the volume of the SMC sampled, there is good agreement between our results and maps created using young stars. In contrast, we find significant discrepancies between our results and maps created using old stars or based on longer wavelength far-IR dust emission that could stem from biased samples in the former and uncertainties in the far-IR emissivity and the optical properties of the dust grains in the latter. This study represents one of the first large-scale categorizations of extragalactic sources behind the SMC and as such we provide the lephare outputs for our full sample of ∼500 000 sources. [ABSTRACT FROM AUTHOR]

We present an 850- μ m mosaic map and extracted catalogue of submillimetre sources in the extended North Ecliptic Pole (NEP) region over about 2 deg2. The 850- μ m map is constructed using newly obtained observations by SCUBA-2 at the East Asian Observatory's James Clerk Maxwell Telescope, carried out using the observatory's large programme opportunities. The recent 850- μ m survey has extended the submillimetre data coverage by almost a factor of 4 compared to previous surveys, with a depth of |$\sigma _\text{rms}\, {=}\, 1.0$| – |$2.3\, {\rm mJy}\, {\rm beam}^{-1}$|⁠. The catalogue contains 549 sources selected above a significance level of 4σ, where the false-detection rate is 10 per cent; a higher threshold of 4.5σ is required in order to achieve a false-detection rate below 3 per cent, which results in 342 sources being selected. Despite the large spatial variation of the noise, the deboosted flux density of sources is comparable to results from the SCUBA-2 Cosmology Legacy Survey, which covered the central 0.6 deg2 of our survey area with better sensitivity. We construct the source counts at 850  μ m, finding results in agreement with other 850- μ m surveys in cosmological blank fields over S 850 = 4–15 mJy. We find a slight excess of bright galaxies (⁠|$S_{850}\, {\gt }\, 15$|  mJy), which can be considered to be at |$z_\text{phot}\, {=}\, 2$| –4. The 850- μ m data add valuable long-wavelength information to mid-infrared-selected sources from the AKARI NEP-deep and NEP-wide surveys, which will be helpful in preparing for future near-infrared to millimetre wavelength observations in the NEP region. Our 850- μ m mosaic map and source catalogue will be made publicly available. [ABSTRACT FROM AUTHOR]

We apply the spectral energy distribution (SED) fitting code ProSpect to multiwavelength imaging for ∼7000 galaxies from the GAMA survey at z < 0.06, in order to extract their star formation histories. We combine a parametric description of the star formation history with a closed-box evolution of metallicity where the present-day gas-phase metallicity of the galaxy is a free parameter. We show with this approach that we are able to recover the observationally determined cosmic star formation history (CSFH), an indication that stars are being formed in the correct epoch of the Universe, on average, for the manner in which we are conducting SED fitting. We also show the contribution to the CSFH of galaxies of different present-day visual morphologies and stellar masses. Our analysis suggests that half of the mass in present-day elliptical galaxies was in place 11 Gyr ago. In other morphological types, the stellar mass formed later, up to 6 Gyr ago for present-day irregular galaxies. Similarly, the most massive galaxies in our sample were shown to have formed half their stellar mass by 11 Gyr ago, whereas the least massive galaxies reached this stage as late as 4 Gyr ago (the well-known effect of 'galaxy downsizing'). Finally, our metallicity approach allows us to follow the average evolution in gas-phase metallicity for populations of galaxies and extract the evolution of the cosmic metal mass density in stars and in gas, producing results in broad agreement with independent, higher redshift observations of metal densities in the Universe. [ABSTRACT FROM AUTHOR]

We present an 850- μ m mosaic map and extracted catalogue of submillimetre sources in the extended North Ecliptic Pole (NEP) region over about 2 deg2. The 850- μ m map is constructed using newly obtained observations by SCUBA-2 at the East Asian Observatory's James Clerk Maxwell Telescope, carried out using the observatory's large programme opportunities. The recent 850- μ m survey has extended the submillimetre data coverage by almost a factor of 4 compared to previous surveys, with a depth of |$\sigma _\text{rms}\, {=}\, 1.0$| – |$2.3\, {\rm mJy}\, {\rm beam}^{-1}$|⁠. The catalogue contains 549 sources selected above a significance level of 4σ, where the false-detection rate is 10 per cent; a higher threshold of 4.5σ is required in order to achieve a false-detection rate below 3 per cent, which results in 342 sources being selected. Despite the large spatial variation of the noise, the deboosted flux density of sources is comparable to results from the SCUBA-2 Cosmology Legacy Survey, which covered the central 0.6 deg2 of our survey area with better sensitivity. We construct the source counts at 850  μ m, finding results in agreement with other 850- μ m surveys in cosmological blank fields over S 850 = 4–15 mJy. We find a slight excess of bright galaxies (⁠|$S_{850}\, {\gt }\, 15$|  mJy), which can be considered to be at |$z_\text{phot}\, {=}\, 2$| –4. The 850- μ m data add valuable long-wavelength information to mid-infrared-selected sources from the AKARI NEP-deep and NEP-wide surveys, which will be helpful in preparing for future near-infrared to millimetre wavelength observations in the NEP region. Our 850- μ m mosaic map and source catalogue will be made publicly available. [ABSTRACT FROM AUTHOR]

Context. The next generation of extensive and data-intensive surveys are bound to produce a vast amount of data, which can be efficiently dealt with using machine-learning and deep-learning methods to explore possible correlations within the multi-dimensional parameter space. Aims. We explore the classification capabilities of convolution neural networks (CNNs) to identify galaxy cluster members (CLMs) by using Hubble Space Telescope (HST) images of fifteen galaxy clusters at redshift 0.19 ≲ z ≲ 0.60, observed as part of the CLASH and Hubble Frontier Field programmes. Methods. We used extensive spectroscopic information, based on the CLASH-VLT VIMOS programme combined with MUSE observations, to define the knowledge base. We performed various tests to quantify how well CNNs can identify cluster members on ht basis of imaging information only. Furthermore, we investigated the CNN capability to predict source memberships outside the training coverage, in particular, by identifying CLMs at the faint end of the magnitude distributions. Results. We find that the CNNs achieve a purity-completeness rate ≳90%, demonstrating stable behaviour across the luminosity and colour of cluster galaxies, along with a remarkable generalisation capability with respect to cluster redshifts. We concluded that if extensive spectroscopic information is available as a training base, the proposed approach is a valid alternative to catalogue-based methods because it has the advantage of avoiding photometric measurements, which are particularly challenging and time-consuming in crowded cluster cores. As a byproduct, we identified 372 photometric cluster members, with mag(F814) < 25, to complete the sample of 812 spectroscopic members in four galaxy clusters RX J2248-4431, MACS J0416-2403, MACS J1206-0847 and MACS J1149+2223. Conclusions. When this technique is applied to the data that are expected to become available from forthcoming surveys, it will be an efficient tool for a variety of studies requiring CLM selection, such as galaxy number densities, luminosity functions, and lensing mass reconstruction. [ABSTRACT FROM AUTHOR]

Aims. Distances and radial velocities of galaxies in the vicinity of the luminous early-type galaxy M 104 (Sombrero) are used to derive its dark matter mass. Methods. Two dwarf galaxies: UGCA 307 and KKSG 30 situated near M 104 were observed with the Advanced Camera for Surveys on the Hubble Space Telescope. The distances 9.03−0.51+0.84 9. 03 − 0.51 + 0.84 $ 9.03^{+0.84}_{-0.51} $ Mpc (UGCA 307) and 9.72−0.41+0.44 9. 72 − 0.41 + 0.44 $ 9.72^{+0.44}_{-0.41} $ Mpc (KKSG 30) were determined using the tip of the red giant branch method. These distances are consistent with the dwarf galaxies being satellites of Sombrero. Results. Using radial velocities and projected separations of UGCA 307, KKSG 30, and a third galaxy with an accurate distance (KKSG 29), as well as 12 other assumed companions with less accurate distances, the total mass of M 104 is estimated to be (1.55 ± 0.49) × 1013 M⊙. At the K-band luminosity of the Sombrero galaxy of 2.4 × 1011 L⊙, its total mass-to-luminosity ratio is MT/LK = (65 ± 20) M⊙/L⊙, which is about three times higher than that of luminous bulgeless galaxies. [ABSTRACT FROM AUTHOR]

The central regions of disc galaxies hold clues to the processes that dominate their formation and evolution. To exploit this, the TIMER project has obtained high signal-to-noise and spatial resolution integral-field spectroscopy data of the inner few kpc of 21 nearby massive barred galaxies, which allows studies of the stellar kinematics in their central regions with unprecedented spatial resolution. We confirm theoretical predictions of the effects of bars on stellar kinematics and identify box/peanuts through kinematic signatures in mildly and moderately inclined galaxies, finding a lower limit to the fraction of massive barred galaxies with box/peanuts at ∼62%. Further, we provide kinematic evidence of the connection between barlenses, box/peanuts, and bars. We establish the presence of nuclear discs in 19 galaxies and show that their kinematics are characterised by near-circular orbits with low pressure support and that they are fully consistent with the bar-driven secular evolution picture for their formation. In fact, we show that these nuclear discs have, in the region where they dominate, larger rotational support than the underlying main galaxy disc. In addition, we define a kinematic radius for the nuclear discs and show that it relates to bar radius, ellipticity and strength, and bar-to-total ratio. Comparing our results with photometric studies of galaxy bulges, we find that careful, state-of-the-art galaxy image decompositions are generally able to discern nuclear discs from classical bulges if the images employed have high enough physical spatial resolution. In fact, we show that nuclear discs are typically identified in such image decompositions as photometric bulges with (near-)exponential profiles. However, we find that the presence of composite bulges (galaxies hosting both a classical bulge and a nuclear disc) can often be unnoticed in studies based on photometry alone and suggest a more stringent threshold to the Sérsic index to identify galaxies with pure classical bulges. [ABSTRACT FROM AUTHOR]

In this paper, we extend the source detection in the GOODS-ALMA field (69 arcmin2, 1σ ≃ 0.18 mJy beam−1) to deeper levels than presented in our previous work. Using positional information at 3.6 and 4.5 μm (from Spitzer-IRAC) as well as the Very Large Array (VLA) at 3 GHz, we explore the presence of galaxies detected at 1.1 mm with ALMA below our original blind detection limit of 4.8-σ, at which the number of spurious sources starts to dominate over that of real sources. In order to ensure the most reliable counterpart association possible, we have investigated the astrometry differences between different instruments in the GOODS–South field. In addition to a global offset between the Atacama Large Millimeter/submillimeter Array (ALMA) and the Hubble Space Telescope (HST) already discussed in previous studies, we have highlighted a local offset between ALMA and the HST that was artificially introduced in the process of building the mosaic of the GOODS–South image. We created a distortion map that can be used to correct for these astrometric issues. In this Supplementary Catalog, we find a total of 16 galaxies, including two galaxies with no counterpart in HST images (also known as optically dark galaxies), down to a 5σ limiting depth of H = 28.2 AB (HST/WFC3 F160W). This brings the total sample of GOODS-ALMA 1.1 mm sources to 35 galaxies. Galaxies in the new sample cover a wider dynamic range in redshift (z = 0.65−4.73), are on average twice as large (1.3 vs 0.65 kpc), and have lower stellar masses (M⋆SC M ⋆ SC $ M_{\star}^{\mathrm{SC}} $ = 7.6 × 1010 M⊙ vs M⋆MC M ⋆ MC $ M_{\star}^{\mathrm{MC}} $ = 1.2 × 1011 M⊙). Although exhibiting larger physical sizes, these galaxies still have far-infrared sizes that are significantly more compact than inferred from their optical emission. [ABSTRACT FROM AUTHOR]

Cosmological analyses of galaxy surveys rely on knowledge of the redshift distribution of their galaxy sample. This is usually derived from a spectroscopic and/or many-band photometric calibrator survey of a small patch of sky. The uncertainties in the redshift distribution of the calibrator sample include a contribution from shot noise, or Poisson sampling errors, but, given the small volume they probe, they are dominated by sample variance introduced by large-scale structures. Redshift uncertainties have been shown to constitute one of the leading contributions to systematic uncertainties in cosmological inferences from weak lensing and galaxy clustering, and hence they must be propagated through the analyses. In this work, we study the effects of sample variance on small-area redshift surveys, from theory to simulations to the COSMOS2015 data set. We present a three-step Dirichlet method of resampling a given survey-based redshift calibration distribution to enable the propagation of both shot noise and sample variance uncertainties. The method can accommodate different levels of prior confidence on different redshift sources. This method can be applied to any calibration sample with known redshifts and phenotypes (i.e. cells in a self-organizing map , or some other way of discretizing photometric space), and provides a simple way of propagating prior redshift uncertainties into cosmological analyses. As a worked example, we apply the full scheme to the COSMOS2015 data set, for which we also present a new, principled SOM algorithm designed to handle noisy photometric data. We make available a catalogue of the resulting resamplings of the COSMOS2015 galaxies. [ABSTRACT FROM AUTHOR]