No Arabic abstract
Using photometric galaxies from the HSC survey, we measure the stellar mass density profiles for satellite galaxies as a function of the projected distance, $r_p$, to isolated central galaxies (ICGs) selected from SDSS/DR7 spectroscopic galaxies at $zsim0.1$. By stacking HSC images, we also measure the projected stellar mass density profiles for ICGs and their stellar halos. The total mass distributions are further measured from HSC weak lensing signals. ICGs dominate within $sim$0.15 times the halo virial radius ($0.15R_{200}$). The stellar mass versus total mass fractions drop with the increase in $r_p$ up to $sim0.15R_{200}$, beyond which they are less than 1% while stay almost constant, indicating the radial distribution of satellites trace dark matter. The total stellar mass in satellites is proportional to the virial mass of the host halo, $M_{200}$, for ICGs more massive than $10^{10.5}M_odot$, i.e., $M_{ast,mathrm{sat}} propto M_{200}$, whereas the relation between the stellar mass of ICGs $+$ stellar halos and $M_{200}$ is close to $M_{ast,mathrm{ICG+diffuse}}propto M_{200}^{1/2}$. Below $10^{10.5}M_odot$, the change in $M_{200}$ is much slower with the decrease in $M_{ast,mathrm{ICG+diffuse}}$. At fixed stellar mass, red ICGs are hosted by more massive dark matter halos and have more satellites. At $M_{200}sim10^{12.7}M_odot$, both $M_{ast,mathrm{sat}}$ and the fraction of stellar mass in satellites versus total stellar mass, $f_mathrm{sat}$, tend to be slightly higher around blue ICGs, perhaps implying the late formation of blue galaxies. $f_mathrm{sat}$ increases with the increase in both $M_{ast,mathrm{ICG+diffuse}}$ and $M_{200}$, and scales more linearly with $M_{200}$. We provide best-fitting formulas for these scaling relations and for red and blue ICGs separately.
We study the faint stellar halo of isolated central galaxies, by stacking galaxy images in the HSC survey and accounting for the residual sky background sampled with random points. The surface brightness profiles in HSC $r$-band are measured for a wide range of galaxy stellar masses ($9.2<log_{10}M_ast/M_odot<11.4$) and out to 120 kpc. Failing to account for the stellar halo below the noise level of individual images will lead to underestimates of the total luminosity by $leq 15%$. Splitting galaxies according to the concentration parameter of their light distributions, we find that the surface brightness profiles of low concentration galaxies drop faster between 20 and 100 kpc than those of high concentration galaxies. Albeit the large galaxy-to-galaxy scatter, we find a strong self-similarity of the stellar halo profiles. They show unified forms once the projected distance is scaled by the halo virial radius. The colour of galaxies is redder in the centre and bluer outside, with high concentration galaxies having redder and more flattened colour profiles. There are indications of a colour minimum, beyond which the colour of the outer stellar halo turns red again. This colour minimum, however, is very sensitive to the completeness in masking satellite galaxies. We also examine the effect of the extended PSF in the measurement of the stellar halo, which is particularly important for low mass or low concentration galaxies. The PSF-corrected surface brightness profile can be measured down to $sim$31 $mathrm{mag}/mathrm{arcsec}^2$ at 3-$sigma$ significance. PSF also slightly flattens the measured colour profiles.
The unprecedented depth and area surveyed by the Subaru Strategic Program with the Hyper Suprime-Cam (HSC-SSP) have enabled us to construct and publish the largest distant cluster sample out to $zsim 1$ to date. In this exploratory study of cluster galaxy evolution from $z=1$ to $z=0.3$, we investigate the stellar mass assembly history of brightest cluster galaxies (BCGs), evolution of stellar mass and luminosity distributions, stellar mass surface density profile, as well as the population of radio galaxies. Our analysis is the first high redshift application of the top N richest cluster selection, which is shown to allow us to trace the cluster galaxy evolution faithfully. Over the 230 deg$^2$ area of the current HSC-SSP footprint, selecting the top 100 clusters in each of the 4 redshift bins allows us to observe the buildup of galaxy population in descendants of clusters whose $zapprox 1$ mass is about $2times 10^{14},M_odot$. Our stellar mass is derived from a machine-learning algorithm, which is found to be unbiased and accurate with respect to the COSMOS data. We find very mild stellar mass growth in BCGs (about 35% between $z=1$ and 0.3), and no evidence for evolution in both the total stellar mass-cluster mass correlation and the shape of the stellar mass surface density profile. We also present the first measurement of the radio luminosity distribution in clusters out to $zsim 1$, and show hints of changes in the dominant accretion mode powering the cluster radio galaxies at $zsim 0.8$.
We present a list of galaxy-scale lens candidates including a highly probable interacting galaxy-scale lens in the Hyper Suprime-Cam (HSC) imaging survey. We combine HSC imaging with the blended-spectra catalog from the Galaxy And Mass Assembly (GAMA) survey to identify lens candidates, and use lens mass modeling to confirm the candidates. We find 46 matches between the HSC S14A_0b imaging data release and the GAMA catalog. Ten of them are probable lens systems according to their morphology and redshifts. There is one system with an interacting galaxy pair, HSC J084928+000949, that has a valid mass model. We predict the total mass enclosed by the Einstein radius of $sim0.72$ ($sim1.65$kpc) for this new expected lens system to be $sim10^{10.59}M_{odot}$. Using the photometry in the {it grizy} bands of the HSC survey and stellar population synthesis modeling with a Salpeter stellar initial mass function, we estimate the stellar mass within the Einstein radius to be $sim10^{10.46},M_{odot}$. We thus find a dark matter mass fraction within the Einstein radius of $sim25%$. Further spectroscopy or high-resolution imaging would allow confirmation of the nature of these lens candidates. The particular system with the interacting galaxy pair, if confirmed, would provide an opportunity to study the interplay between dark matter and stars as galaxies build up through hierarchical mergers.
We present a statistical weak-lensing magnification analysis on an optically selected sample of 3029 texttt{CAMIRA} galaxy clusters with richness $N>15$ at redshift $0.2leq z <1.1$ in the Subaru Hyper Suprime-Cam (HSC) survey. We use two distinct populations of color-selected, flux-limited background galaxies, namely the low-$z$ and high-$z$ samples at mean redshifts of $approx1.1$ and $approx1.4$, respectively, from which to measure the weak-lensing magnification signal by accounting for cluster contamination as well as masking effects. Our magnification bias measurements are found to be uncontaminated according to validation tests against the null-test samples for which the net magnification bias is expected to vanish. The magnification bias for the full texttt{CAMIRA} sample is detected at a significance level of $9.51sigma$, which is dominated by the high-$z$ background. We forward-model the observed magnification data to constrain the normalization of the richness-to-mass ($N$--$M$) relation for the texttt{CAMIRA} sample with informative priors on other parameters. The resulting scaling relation is $Npropto {M_{500}}^{0.92pm0.13} (1 + z)^{-0.48pm0.69}$, with a characteristic richness of $N=left(17.72pm2.60right)$ and intrinsic log-normal scatter of $0.15pm0.07$ at $M_{500} = 10^{14}h^{-1}M_{odot}$. With the derived $N$--$M$ relation, we provide magnification-calibrated mass estimates of individual texttt{CAMIRA} clusters, with the typical uncertainty of $approx39%$ and $approx32%$ at richness$approx20$ and $approx40$, respectively. We further compare our magnification-inferred $N$--$M$ relation with those from the shear-based results in the literature, finding good agreement.
We use galaxy-galaxy lensing to study the dark matter halos surrounding a sample of Locally Brightest Galaxies (LBGs) selected from the Sloan Digital Sky Survey. We measure mean halo mass as a function of the stellar mass and colour of the central galaxy. Mock catalogues constructed from semi-analytic galaxy formation simulations demonstrate that most LBGs are the central objects of their halos, greatly reducing interpretation uncertainties due to satellite contributions to the lensing signal. Over the full stellar mass range, $10.3 < log [M_*/M_odot] < 11.6$, we find that passive central galaxies have halos that are at least twice as massive as those of star-forming objects of the same stellar mass. The significance of this effect exceeds $3sigma$ for $log [M_*/M_odot] > 10.7$. Tests using the mock catalogues and on the data themselves clarify the effects of LBG selection and show that it cannot artificially induce a systematic dependence of halo mass on LBG colour. The bimodality in halo mass at fixed stellar mass is reproduced by the astrophysical model underlying our mock catalogue, but the sign of the effect is inconsistent with recent, nearly parameter-free age-matching models. The sign and magnitude of the effect can, however, be reproduced by halo occupation distribution models with a simple (few-parameter) prescription for type-dependence.