Counting galaxy number density with wide range sky surveys has been well adopted in researches focusing on revealing evolution pattern of different types of galaxies. As understood intuitively the astrophysics environment physics is intimated affected by cosmology priors with theoretical estimation or vise versa, or simply stating that the astrophysics effect couples the corresponding cosmology observations
or the way backwards. In this article we try to quantify the influence on galaxy number density prediction at faint luminosity limit from the uncertainties in cosmology, and how much the uncertainties blur the detection of galaxy evolution, with the hope that this trying may indeed help for precise and physical cosmology study in near future or vise versa
With the Hubble Frontier Fields program, gravitational lensing has provided a powerful way to extend the study of the ultraviolet luminosity function (LF) of galaxies at $z \sim 6$ down to unprecedented magnitude limits. At the same time, significant discrepancies between different studies were found at the very faint end of the LF. In an attempt to understand such disagreements, we present a comprehensive assessment of the uncertainties associated with the lensing models and the size distribution of galaxies. We use end-to-end simulations from the source plane to the final LF that account for…
We present the faint end of number counts at 1.3 mm (238 GHz) obtained with the Atacama Large Millimeter/submillimeter Array (ALMA). Band 6 observations were carried out targeting 20 star-forming galaxies at z ~ 1.4 in the Subaru/XMM-Newton Deep Survey field. In the observations, we serendipitously detect 15 sources (>=3.8 sigma, S(1.3 mm) = 0.15-0.61 mJy) other than the targeted sources. We create number counts by using these `sub-mJy sources', which probe the faintest flux range among surveys at millimeter wavelengths. The number counts are consistent with (flux-scaled) number counts at 850 …
We present a new technique to estimate the evolution of the very faint end of the UV luminosity function (LF) out to $z\sim5$. Measured star formation histories (SFHs) from the fossil record of Local Group galaxies are used to reconstruct the LF down to M$_{UV}\sim-5$ at $z\sim5$ and M$_{UV}\sim-1.5$ at $z<1$. Such faint limits are well beyond the current observational limits and are likely to remain beyond the limits of next generation facilities. The reconstructed LFs, when combined with direct measurements of the LFs at higher luminosity, are well-fit by a standard Schechter function with n…
We present the statistics of faint submillimeter/millimeter galaxies (SMGs) and serendipitous detections of a submillimeter/millimeter line emitter (SLE) with no multi-wavelength continuum counterpart revealed by the deep ALMA observations. We identify faint SMGs with flux densities of 0.1-1.0 mJy in the deep Band 6 and Band 7 maps of 10 independent fields that reduce cosmic variance effects. The differential number counts at 1.2 mm are found to increase with decreasing flux density down to 0.1 mJy. Our number counts indicate that the faint (0.1-1.0 mJy, or SFR_IR ~ 30-300 Msun/yr) SMGs contri…
The shape of the curves defined by the counts of radio sources per unit area as a function of their flux density was one of the earliest cosmological probes. Radio source counts continue to be an area of interest, used to study the relative populations of galaxy types in the Universe (as well as investigate any cosmological evolution in luminosity functions). They are a vital consideration for determining how source confusion may limit the depth of a radio interferometer observation, and are essential for characterising extragalactic foregrounds in CMB experiments. There is currently no consen…
We present statistics of 133 faint 1.2-mm continuum sources detected in about 120 deep ALMA pointing data that include all the archival deep data available by 2015 June. We derive number counts of 1.2 mm continuum sources down to 0.02 mJy partly with the assistance of gravitational lensing, and find that the total integrated 1.2 mm flux of the securely identified sources is 22.9^(+6.7)_(-5.6) Jy deg^(-2) that corresponds to 104^(+31)_(-25) % of the extragalactic background light (EBL) measured by COBE observations. These results suggest that the major 1.2 mm EBL contributors are sources with 0…
We present the results of SCUBA2 observations at 450 micron and 850 micron of the field lensed by the massive cluster A370. With a total survey area > 100 arcmin2 and 1 sigma sensitivities of 3.92 and 0.82 mJy/beam at 450 and 850 micron respectively, we find a secure sample of 20 sources at 450 micron and 26 sources at 850 micron with a signal-to-noise ratio > 4. Using the latest lensing model of A370 and Monte Carlo simulations, we derive the number counts at both wavelengths. The 450 micron number counts probe a factor of four deeper than the counts recently obtained from the Herschel Space …
We present measurements of a population of matched radio sources at 1.4 and 5 GHz down to a flux limit of 1.5 mJy in 7 sq. degs. of the NOAO Deep Field South. We find a significant fraction of sources with inverted spectral indices that all have 1.4 GHz fluxes less than 10 mJy, and are therefore too faint to have been detected and included in previous radio source count models that are matched at multiple frequencies. Combined with the matched source population at 1.4 and 5 GHz in 1 sq. deg. in the ATESP survey, we update models for the 5 GHz differential number counts and distributions of spe…
We exploit a sample of ultra-faint high-redshift galaxies (demagnified HST $H_{160}$ magnitude $>30$) in the Frontier Fields clusters A2744 and M0416 to constrain a theoretical model for the UV luminosity function (LF) in the presence of photoionization feedback. The objects have been selected on the basis of accurate photometric redshifts computed from multi-band photometry including 7 HST bands and deep $K_s$ and IRAC observations. Magnification is computed on an object-by-object basis from all available lensing models of the two clusters. We take into account source detection completeness a…
Context. Infrared Faint Radio Sources (IFRS) are extragalactic emitters clearly detected at radio wavelengths but barely detected or undetected at optical and infrared wavelengths, with 5 sigma sensitivities as low as 1 uJy. Aims. Recent SED-modelling and analysis of their radio properties shows that IFRS are consistent with a population of (potentially extremely obscured) high-redshift AGN at 3<z<6. We demonstrate some astrophysical implications of this population and compare them to predictions from models of galaxy evolution and structure formation. Methods. We compiled a list of IFRS from …
We present the rest-frame V-band luminosity function (LF) of galaxies at 0.4<z<4.0, measured from a near-infrared selected sample constructed from the NMBS, the FIRES, the FIREWORKS, and the ultra-deep NICMOS and WFC3 observations in the HDFN, HUDF, and GOODS-CDFS, all having high-quality optical to mid-infrared data. This unique sample combines data from surveys with a large range of depths and areas in a self-consistent way, allowing us to (1) minimize the uncertainties due to cosmic variance; and (2) simultaneously constrain the bright and faint ends with unprecedented accuracy over the tar…
We present mid-infrared galaxy number counts based on the Early Release Observations obtained by the James Webb Space Telescope (JWST) at 7.7-, 10- and 15-$μ$m (F770W, F1000W and F1500W, respectively) bands of the Mid-Infrared Instrument (MIRI). Due to the superior sensitivity of JWST, the 80 percent completeness limits reach 0.32, 0.79 and 2.0 $μ$Jy in F770W, F1000W and F1500W filters, respectively, i.e., $\sim$100 times deeper than previous space infrared telescopes such as Spitzer or AKARI. The number counts reach much deeper than the broad bump around $0.05\sim0.5$ mJy due to polycyclic ar…
Star forming galaxies are thought to dominate the sub-mJy radio population, but recent work has shown that low luminosity AGN can still make a significant contribution to the faint radio source population. Spectral indices are an important tool for understanding the emission mechanism of the faint radio sources. We have observed the extended Chandra Deep Field South at 5.5 GHz using a mosaic of 42 pointings with the Australia Telescope Compact Array (ATCA). Our image reaches an almost uniform sensitivity of ~12 microJy rms over 0.25 deg^2 with a restoring beam of 4.9 x 2.0 arcsec, making it on…
It has recently been shown that galaxy formation models within the LambdaCDM cosmology predict that, compared to the observed population, small galaxies (with stellar masses < 10^{11} M_sun) form too early, are too passive since z ~ 3 and host too old stellar populations at z=0. We then expect an overproduction of small galaxies at z > 4 that should be visible as an excess of faint Lyman-break galaxies. To check whether this excess is present, we use the MORGANA galaxy formation model and GRASIL spectro-photometric + radiative transfer code to generate mock catalogues of deep fields observed w…
Recent observations have constrained the galaxy UV luminosity function up to z~10. However, these observations alone allow for a wide range of reionization scenarios due to uncertainties in the abundance of faint galaxies and the escape fraction of ionizing photons. We show that requiring continuity with post-reionization (z<6) measurements, where the Lya forest provides a complete probe of the cosmological emissivity of ionizing photons, significantly reduces the permitted parameter space. Models that are simultaneously consistent with the measured UV luminosity function, the Thomson optical …
Supernova cosmology without spectra will be an important component of future surveys such as LSST. This lack of supernova spectra results in uncertainty in the redshifts which, if ignored, leads to significantly biased estimates of cosmological parameters. Here we present a hierarchical Bayesian formalism -- zBEAMS -- that addresses this problem by marginalising over the unknown or uncertain supernova redshifts to produce unbiased cosmological estimates that are competitive with supernova data with spectroscopically confirmed redshifts. zBEAMS provides a unified treatment of both photometric r…
Ruminations Upon the Modeling of X-ray Foregrounds, Backgrounds and Faint Sources
Kavli Institute for Particle Astrophysics and Cosmology, Stanford University（斯坦福大学卡弗里粒子天体物理与宇宙学研究所）；Department of Physics, Stanford University（斯坦福大学物理系）；SLAC National Accelerator Laboratory（SLAC国家加速器实验室）；Department of Physics and Astronomy, Rutgers University（罗格斯大学物理与天文系）；Department of Physics, Faculty of Science, Chulalongkorn University（朱拉隆功理学院物理系）
Department of Astrophysics, University of Vienna（维也纳大学天体物理系）；CERN, Theoretical Physics Department（欧洲核子研究中心理论物理部）
The two leading hypotheses for the Galactic Center Excess (GCE) in the $\textit{Fermi}$ data are an unresolved population of faint millisecond pulsars (MSPs) and dark-matter (DM) annihilation. The dichotomy between these explanations is typically reflected by modeling them as two separate emission components. However, point-sources (PSs) such as MSPs become statistically degenerate with smooth Poisson emission in the ultra-faint limit (formally where each source is expected to contribute much less than one photon on average), leading to an ambiguity that can render questions such as whether th…
