Illuminating Low-Surface-Brightness Galaxies with the Hyper Suprime-Cam Survey
Johnny P. Greco, Jenny E. Greene, Michael A. Strauss, Lauren A. MacArthur, Xzavier Flowers, Andy D. Goulding, Song Huang, Ji Hoon Kim, Yutaka Komiyama, Alexie L… 展开作者
Johnny P. Greco, Jenny E. Greene, Michael A. Strauss, Lauren A. MacArthur, Xzavier Flowers, Andy D. Goulding, Song Huang, Ji Hoon Kim, Yutaka Komiyama, Alexie Leauthaud, Lukas Leisman, Robert H. Lupton, Cristóbal Sifón, Shiang-Yu Wang
备注：
21 pages, 14 figures, 1 table; accepted for publication in ApJ
We present a catalog of extended low-surface-brightness galaxies (LSBGs) identified in the Wide layer of the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP). Using the first ${\sim}$200 deg$^2$ of the survey, we have uncovered 781 LSBGs, spanning red ($g-i\geq0.64$) and blue ($g-i<0.64$) colors and a wide range of morphologies. Since we focus on extended galaxies ($r_\mathrm{eff}=2.5$-$14^{\prime\prime}$), our sample is likely dominated by low-redshift objects. We define LSBGs to have mean surface brightnesses $\barμ_\mathrm{eff}(g)>24.3$ mag arcsec$^{-2}$, which allows nucleated galaxies into our sample. As a result, the central surface brightness distribution spans a wide range of $μ_0(g)=18$-$27.4$ mag arcsec$^{-2}$, with 50% and 95% of galaxies fainter than 24.3 and 22 mag arcsec$^{-2}$, respectively. Furthermore, the surface brightness distribution is a strong function of color, with the red distribution being much broader and generally fainter than that of the blue LSBGs, and this trend shows a clear correlation with galaxy morphology. Red LSBGs typically have smooth light profiles that are well-characterized by single-component Sérsic functions. In contrast, blue LSBGs tend to have irregular morphologies and show evidence for ongoing star formation. We crossmatch our sample with existing optical, HI, and ultraviolet catalogs to gain insight into the physical nature of the LSBGs. We find that our sample is diverse, ranging from dwarf spheroidals and ultra-diffuse galaxies in nearby groups to gas-rich irregulars to giant LSB spirals, demonstrating the potential of the HSC-SSP to provide a truly unprecedented view of the LSBG population.
We have surveyed a complete extent of Leo A - an apparently isolated gas-rich low-mass dwarf irregular galaxy in the Local Group. The $B$, $V$, and $I$ passband CCD images (typical seeing $\sim$0.8") were obtained with Subaru Telescope equipped with Suprime-Cam mosaic camera. The wide-field ($20' \times 24'$) photometry catalog of 38,856 objects ($V \sim 16-26$ mag) is presented. This survey is also intended to serve as "a finding chart" for future imaging and spectroscopic observation programs of Leo A.
We have measured the absolute proper motion of the Sextans dwarf spheroidal galaxy using Subaru Suprime-Cam images taken at three epochs, with a time baseline of ~ 10 years. We astrometrically calibrate each epoch by constructing distortion-correction maps from the best available Subaru Suprime-Cam dithered data sets and from Gaia DR1 positions. The magnitude limit of the proper-motion study is V ~ 24. The area covered is 26.7 x 23.3 arcmin, which is still within the core radius of Sextans. The derived proper motion is (mu_a, mu_d) = (-0.409 +/- 0.050, -0.047 +/- 0.058) mas/yr. The direction o…
The Wide Chandra Deep Field-South (W-CDF-S) field is one of the SERVS fields with extensive multiwavelength datasets, which can provide insights into the nature and properties of objects in this field. However, the public optical data from DES ($grizy$ to $m\rm_{AB} \approx 21.4-24.3$) are not sufficiently deep to match well the NIR data from VIDEO ($ZYJHK_s$ to $m\rm_{AB} \approx 23.5-25.7$), which limits the investigation of fainter objects at higher redshifts. Here, we present an optical catalog of $\approx$ 2,000,000 objects in W-CDF-S utilizing archival Hyper Suprime-Cam observations in t…
We present a description of the second data release for the photometric redshift (photo-$z$) of the Subaru Strategic Program for the Hyper-Suprime Cam survey. Our photo-$z$ products for the entire area in the Data Release 2 are publicly available, and both our point estimate catalog products and full PDFs can be retrieved from the data release site, \url{https://hsc-release.mtk.nao.ac.jp/}.
The Milky Way Tomography with Subaru Hyper Suprime-Cam. I. Halo substructures
Astronomical Institute, Tohoku University（东北大学天文学研究所）；Department of Advanced Sciences, Faculty of Science and Engineering, Hosei University（法政大学理工学部先进科学科）；National Institute of Technology, Sendai College（仙台工业高等专门学校）；National Astronomical Observatory of Japan（日本国立天文台）；The Graduate University for Advanced Studies（综合研究大学院大学）；Department of Astrophysical Sciences, Princeton University（普林斯顿大学天体物理学系）；Kavli Institute for the Physics and Mathematics of the Universe（Kavli宇宙物理数学研究所）
We have measured the absolute proper motion of the Draco dwarf spheroidal galaxy using Subaru Suprime-Cam images taken at three epochs, with time baselines of 4.4 and 7 years. The magnitude limit of the proper-motion study is i=25, thus allowing for thousands of background galaxies and Draco stars to be used to perform extensive astrometric tests and to derive the correction to an inertial reference frame. The derived proper motion is (mu_alpha, mu_delta) =(-0.284 +- 0.047, -0.289 +-0.041) mas/yr. This motion implies an orbit that takes Draco to a pericenter of $\sim 20$ kpc; a somewhat disrup…
We exploit the exquisite, deep Hyper Suprime-Cam (HSC) imaging data to probe the Galactic halo out to 200 kpc. Using the ~100 square degree, multi-band photometry of the first HSC Wide survey data release, we identify blue horizontal branch (BHB) stars beyond 50 kpc in the halo. The presence of the Sagittarius (Sgr) stream in the HSC fields produces a notable excess of stars at the apocentre of the leading arm (~50-60 kpc). For fields excluding Sgr, the BHB counts are consistent with a continuation of a -4 power-law from the inner halo. However, we find that the majority of the non-Sgr BHB sta…
Surface brightness fluctuation (SBF) magnitudes are a powerful standard candle to measure distances to semi-resolved galaxies in the local universe, a majority of which are dwarf galaxies that have often bluer colors than bright early-type galaxies. We present an empirical $i-$band SBF calibration in a blue regime, $0.2 \lesssim (g-i)_0 \lesssim 0.8$ in the Hyper Suprime-Cam (HSC) magnitude system. We measure SBF magnitudes for 12 nearby dwarf galaxies of various morphological types with archival HSC imaging data, and use their tip of the red giant branch (TRGB) distances to derive fluctuation…
We present the deep and wide $V$ and $I_c$ photometry of the Sextans dwarf spheroidal galaxy (dSph) taken by Suprime-Cam imager on the Subaru Telescope, which extends out to the tidal radius. The colour-magnitude diagram (CMD) reaches two magnitudes below the main sequence (MS) turn-off, showing a steep red giant branch, blue and red horizontal branch (HB), sub-giant branch (SGB), MS, and blue stragglers (BS). We construct the radial profile of each evolutionary phase and demonstrate that blue HB stars are more spatially extended, while red HB stars are more centrally concentrated than the oth…
This study investigates the role of large-scale environments on the fraction of spiral galaxies at $z=$ 0.3-0.6 sliced to three redshift bins of $Δz=0.1$. Here, we sample 276220 massive galaxies in a limited stellar mass of $5\times10^{10}$ solar mass ($\sim M^\ast$) over 360 deg$^2$, as obtained from the Second Public Data Release of the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP). By combining projected two-dimensional density information (Shimakawa et al. 2021) and the CAMIRA cluster catalog (Oguri et al. 2018), we investigate the spiral fraction across large-scale overdensities an…
Using the first 50% of data collected for the Spitzer Large Area Survey with Hyper-Suprime-Cam (SPLASH) observations on the 1.8 deg$^2$ Cosmological Evolution Survey (COSMOS) we estimate the masses and star formation rates of 3398 $M_*>10^{10}M_\odot $ star-forming galaxies at $4 < z < 6$ with a substantial population up to $M_* \gtrsim 10^{11.5} M_\odot$. We find that the strong correlation between stellar mass and star formation rate seen at lower redshift (the "main sequence" of star-forming galaxies) extends to $z\sim6$. The observed relation and scatter is consistent with a continued incr…
We present a catalogue of low surface brightness (LSB) galaxies in the Coma cluster obtained from deep Subaru/Suprime-Cam V and R-band imaging data within a region of $\sim$4 deg$^2$. We increase the number of LSB galaxies presented in Yagi et al. (2016) by a factor of $\sim$3 and report the discovery of 29 new ultra-diffuse galaxies (UDGs). We compile the largest sample of ultra-diffuse galaxies with colours and structural parameters in the Coma cluster. While most UDGs lie along the red-sequence relation of the colour-magnitude diagram, $\sim$5per cent are outside (bluer or redder) the red-s…
We carry out a search for strong-lens systems containing high-redshift lens galaxies with the goal of extending strong-lensing-assisted galaxy evolutionary studies to earlier cosmic time. Two strong-lens classifiers are constructed from a deep residual network and trained with datasets of different lens-redshift and brightness distributions. We classify a sample of 5,356,628 pre-selected objects from the Wide-layer fields in the second public data release of the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) by applying the two classifiers to their HSC $gri$-filter cutouts. Cutting off a…
The Milky Way Tomography with Subaru Hyper Suprime-Cam. II. Global halo structure
Astronomical Institute, Tohoku University（东北大学天文学研究所）；The William H. Miller III, Dept. of Physics & Astronomy, Johns Hopkins University（约翰斯·霍普金斯大学物理与天文学系威廉·H·米勒三世楼）
Photometric redshifts are a key component of many science objectives in the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP). In this paper, we describe and compare the codes used to compute photometric redshifts for HSC-SSP, how we calibrate them, and the typical accuracy we achieve with the HSC five-band photometry (grizy). We introduce a new point estimator based on an improved loss function and demonstrate that it works better than other commonly used estimators. We find that our photo-z's are most accurate at 0.2<~zphot<~1.5, where we can straddle the 4000A break. We achieve sigma(d_z…
The Milky Way Tomography with Subaru Hyper Suprime-Cam: Implications for the past orbit of the Large Magellanic Cloud
Astronomical Institute, Tohoku University（东北大学天文学研究所）；The William H. Miller III, Dept. of Physics & Astronomy, Johns Hopkins University（约翰斯·霍普金斯大学物理与天文系威廉·H·米勒三世中心）
We present a preview of the faint dwarf galaxy discoveries that will be possible with the Vera C. Rubin Observatory and Subaru Hyper Suprime-Cam in the next decade. In this work, we combine deep ground-based images from the Panoramic Imaging Survey of Centaurus and Sculptor (PISCeS) and extensive image simulations to investigate the recovery of faint, resolved dwarf galaxies in the Local Volume with a matched-filter technique. We adopt three fiducial distances - 1.5, 3.5, 5 Mpc, and quantitatively evaluate the effects on dwarf detection of varied stellar backgrounds, ellipticity, and Milky Way…
We present a pilot study to assess the potential of Hyper Suprime-Cam Public Data Release 2 (HSC-PDR2) images for the analysis of extended faint structures within groups of galaxies. We examine the intra-group light (IGL) of the group 400138 ($M_{\rm{dyn}}= 1.3 \pm 0.5 \times 10^{13} $M$_{\odot}$, $z\sim 0.2$) from the Galaxy And Mass Assembly (GAMA) survey using Hyper-Suprime Cam Subaru Strategic Program Public Data Release 2 (HSC-PDR2) images in $g$, $r$, and $i$ bands. We present the most extended IGL measurement to date, reaching down to $μ_{g}^{\rm{lim}}=30.76$ mag arcsec$^{-2}$ ($3 σ$; $…
We present the Swimmy (Subaru WIde-field Machine-learning anoMalY) survey program, a deep-learning-based search for unique sources using multicolored ($grizy$) imaging data from the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP). This program aims to detect unexpected, novel, and rare populations and phenomena, by utilizing the deep imaging data acquired from the wide-field coverage of the HSC-SSP. This article, as the first paper in the Swimmy series, describes an anomaly detection technique to select unique populations as "outliers" from the data-set. The model was tested with known ex…
Green valley galaxies represent the population that is likely to transition from the star-forming to the quiescent phases. To investigate the role of the environment in quenching star formation, we use the wide-field data from the Hyper Suprime-Cam Strategic Subaru Proposal survey to quantify the frequency of green valley galaxies in different environments and their redshift evolution. We find that the green valley fraction, in general, is less than 20% in any redshift and environment. The green valley fraction, when normalized to the total population, is higher in the field than that in group…
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…
We present 1,201 galaxies at $0.05<z<0.45$ that host tidal features, detected from the first $\sim\! 200$ deg$^2$ of imaging from the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP). All galaxies in the present sample have spectroscopic observations from the Sloan Digital Sky Survey (SDSS) spectroscopic campaigns, generating a sample of 21208 galaxies. Of these galaxies, we identify 214 shell systems and 987 stream systems. For 575 of these systems, we are additionally able to measure the $(g-i)$ colors of the tidal features. We find evidence for star formation in a subset of the streams,…
We present the first results of a wide-field mapping survey of the M81 group conducted with Hyper Suprime-Cam on the Subaru Telescope. Our deep photometry reaches $\sim2$ magnitudes below the tip of the red giant branch (RGB) and reveals the spatial distribution of both old and young stars over an area of $\sim 100\times115$ kpc at the distance of M81. The young stars ($\sim30-160$ Myr old) closely follow the neutral hydrogen distribution and can be found in a stellar stream between M81 and NGC\,3077 and in numerous outlying stellar associations, including the known concentrations of Arp's Loo…
We utilize the Hyper Suprime-Cam (HSC) Wide Survey to explore the properties of galaxies located in the voids identified from the Baryon Oscillation Spectroscopic Survey (BOSS) up to z~0.7. The HSC reaches i~25, allowing us to characterize the void galaxies down to 10$^{9.2}$ solar mass. We find that the revised void galaxy densities, when including faint galaxies in voids defined by bright galaxies, are still underdense compared to the mean density from the entire field. In addition, we classify galaxies into star-forming, quiescent, and green valley populations, and find that void galaxies t…
We constrain the quasar contribution to cosmic reionization based on our deep optical survey of z~6 quasars down to z_R=24.15 using Subaru/Suprime-Cam in three UKIDSS-DXS fields covering 6.5 deg^2. In Kashikawa et al. (2015), we select 17 quasar candidates and report our initial discovery of two low-luminosity quasars (M_1450~ -23) from seven targets, one of which might be a Lyman alpha emitting galaxy. From an additional optical spectroscopy, none of the four candidates out of the remaining ten turn out to be genuine quasars. Moreover, the deeper optical photometry provided by the Hyper Supri…
We use deep and wide imaging data from the CFHT Large Area U-band Deep Survey (CLAUDS) and the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) to constrain the ionizing radiation (Lyman Continuum; LyC) escape fraction from AGNs at $z \sim 3 - 4$. For 94 AGNs with spectroscopic redshifts at $3.3 < z < 4.0$, we use their U-band / i-band flux ratios to estimate LyC transmission of individual AGNs. The distribution of their LyC transmission shows values lower than the range of LyC transmission values for IGM of the same redshift range, which suggests that LyC escape fraction of AGNs at $z>3.3…
We present the first results of the Subaru/Hyper Suprime-Cam (HSC) survey of the interacting galaxy system, NGC4631 and NGC4656. From the maps of resolved stellar populations, we identify 11 dwarf galaxies (including already-known dwarfs) in the outer region of NGC4631 and the two tidal stellar streams around NGC4631, named Stream SE and Stream NW, respectively. This paper describes the fundamental properties of these tidal streams. Based on the tip of red giant branch method and the Bayesian statistics, we find that StreamSE (7.10 Mpc in Expected a posteriori, EAP, with the 90% credible inter…
Narrow-line regions excited by active galactic nuclei (AGN) are important for studying AGN photoionization and feedback. Their strong [O III] lines can be detected with broadband images, allowing morphological studies of these systems with large-area imaging surveys. We develop a new technique to reconstruct the [O III] images using the Subaru Hyper Suprime-Cam (HSC) Survey aided with spectra from the Sloan Digital Sky Survey (SDSS). The technique involves a careful subtraction of the galactic continuum to isolate emission from the [O III]$λ$5007 and [O III]$λ$4959 lines. Compared to tradition…
We construct a sample of X-ray bright optically faint active galactic nuclei by combining Subaru Hyper Suprime-Cam, XMM-Newton, and infrared source catalogs. 53 X-ray sources satisfying i band magnitude fainter than 23.5 mag and X-ray counts with EPIC-PN detector larger than 70 are selected from 9.1 deg^2, and their spectral energy distributions (SEDs) and X-ray spectra are analyzed. 44 objects with an X-ray to i-band flux ratio F_X/F_i>10 are classified as extreme X-ray-to-optical flux sources. SEDs of 48 among 53 are represented by templates of type 2 AGNs or starforming galaxies and show si…
Active galactic nuclei (AGNs) are key for understanding the coevolution of galaxies and supermassive black holes (SMBHs). AGN activity is thought to affect the properties of their host galaxies, via a process called "AGN feedback", which drives the co-evolution. From a parent sample of 1151 z < 1 type-1 quasars from the Sloan Digital Sky Survey quasar catalog, we detected host galaxies of 862 of them in the high-quality grizy images of the Subaru Hyper Suprime-Cam (HSC) survey. The unprecedented combination of the survey area and depth allows us to perform a statistical analysis of the quasar …
We report on the optical properties of infrared (IR)-bright dust-obscured galaxies (DOGs) that are defined as (i-[22])_AB > 7.0. Because supermassive black holes (SMBHs) in IR-bright DOGs are expected to be rapidly growing in the major merger scenario, they provide useful clues for understanding the co-evolution of SMBHs and their host galaxies. However, the optical properties of IR-bright DOGs remain unclear because the optical emission of a DOG is very faint. By combining ~ 105 deg^2 images of the optical, near-IR, and mid-IR data obtained from the Subaru Hyper Suprime-Cam (HSC) survey, the …
We report an automated morphological classification of galaxies into S-wise spirals, Z-wise spirals, and non-spirals using big image data taken from Subaru/Hyper Suprime-Cam (HSC) Survey and a convolutional neural network(CNN)-based deep learning technique. The HSC i-band images are about 25 times deeper than those from the Sloan Digital Sky Survey (SDSS) and have a two times higher spatial resolution, allowing us to identify substructures such as spiral arms and bars in galaxies at z>0.1. We train CNN classifiers by using HSC images of 1447 S-spirals, 1382 Z-spirals, and 51,650 non-spirals. A…
Massive galaxies display extended light profiles that can reach several hundreds of kilo parsecs. These stellar halos provide a fossil record of galaxy assembly histories. Using data that is both wide (~100 square degree) and deep (i>28.5 mag/arcsec^2 in i-band), we present a systematic study of the stellar halos of a sample of more than 3000 galaxies at 0.3 < z < 0.5 with $\log M_{\star}/M_{\odot} > 11.4$. Our study is based on high-quality (0.6 arcsec seeing) imaging data from the Hyper Suprime-Cam (HSC) Subaru Strategic Program (SSP), which enables us to individually estimate surface mass d…
The Ly$α$ luminosity function (LF) of Ly$α$ emitters (LAEs) has been used to constrain the neutral hydrogen fraction in the intergalactic medium (IGM) and thus the timeline of cosmic reionization. Here we present the results of a new narrow-band imaging survey for $z=7.3$ LAEs in a large area of $\sim 3\ \mathrm{deg}^2$ with Subaru/Hyper Suprime-Cam. No LAEs are detected down to $L_{\mathrm{Ly}α}\simeq 10^{43.2}\ \mathrm{erg\ s^{-1}}$ in an effective cosmic volume of $\sim 2\times 10^6$ Mpc$^3$, placing an upper limit to the bright part of the $z=7.3$ Ly$α$ LF for the first time and confirming…
We report the serendipitous discovery of HSC J0904$-$0102, a quadruply-lensed Lyman break galaxy (LBG) in the Survey of Gravitationally-lensed Objects in Hyper Suprime-Cam Imaging (SuGOHI). Owing to its point-like appearance, the source was thought to be a lensed active galactic nucleus. We obtained follow-up spectroscopic data with the Gemini Multi-Object Spectrographs on the Gemini South Telescope, which confirmed this to be a lens system. The deflecting foreground galaxy is a typical early-type galaxy at a high redshift of $z_{\ell} = 0.957$ with stellar velocity dispersion $σ_v=259\pm56$ k…
This paper presents a thousand passive spiral galaxy samples at $z=$ 0.01-0.3 based on a combined analysis of the Third Public Data Release of the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP PDR3) and the GALEX-SDSS-WISE Legacy Catalog (GSWLC-2). Among 54871 $gri$ galaxy cutouts taken from the HSC-SSP PDR3 over 1072 deg$^2$, we conducted a search with deep-learning morphological classification for candidates of passive spirals below the star-forming main sequence derived by UV to mid-IR SED fitting in the GSWLC-2. We then classified the candidates into 1100 passive spirals and 1141 sec…
We present the quasar luminosity function at $z \sim 5$ derived from the optical wide-field survey data obtained as a part of the Subaru strategic program (SSP) with Hyper Suprime-Cam (HSC). From $\sim$81.8 deg$^2$ area in the Wide layer of the HSC-SSP survey, we selected 224 candidates of low-luminosity quasars at $z \sim 5$ by adopting the Lyman-break method down to $i = 24.1$ mag. Based on our candidates and spectroscopically-confirmed quasars from the Sloan Digital Sky Survey (SDSS), we derived the quasar luminosity function at $z \sim 5$ covering a wide luminosity range of $-28.76 < M_{\r…
We utilize the HSC CAMIRA cluster catalog and the photo-$z$ galaxy catalog constructed in the HSC wide field (S16A), covering $\sim$ 174 deg$^{2}$, to study the star formation activity of galaxies in different environments over 0.2 $<$ $z$ $<$ 1.1. We probe galaxies down to $i \sim$ 26, corresponding to a stellar mass limit of log$_{10}$(M$_*$/M$_{\odot}$) $\sim$ 8.2 and $\sim$ 8.6 for star-forming and quiescent populations, respectively, at $z$ $\sim$ 0.2. The existence of the red sequence for low stellar mass galaxies in clusters suggests that the environmental quenching persists to halt the…
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 $z\sim 1$ 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 sel…
We present wide and deep photometry of the northwest part of the halo of the Andromeda galaxy (M31) using Hyper Suprime-Cam on the Subaru Telescope. The survey covers 9.2 deg$^{2}$ field in the $g$, $i$, and $NB515$ bands and shows a clear red giant branch (RGB) of M31's halo stars and a pronounced red clump (RC) feature. The spatial distribution of RC stars shows a prominent stream feature, the North Western (NW) Stream, and a diffuse substructure in the south part of our survey field. We estimate the distances based on the RC method and obtain $(m-M)$ = 24.63$\pm 0.191$(random)$\pm0.057$(sys…
We present deep, wide-field Subaru Hyper Suprime-Cam photometry of two recently discovered satellites of the Milky Way (MW): Columba I and Triangulum II. The color magnitude diagrams of both objects point to exclusively old and metal-poor stellar populations. We re-derive structural parameters and luminosities of these satellites, and find $M_{\rm V, Col~I} = -4.2\pm0.2$ for Col I and $M_{\rm V, Tri~II} = -1.2\pm0.4$ for Tri II, with corresponding half-light radii of $r_{\rm h, Col~I} = 117\pm17$ pc and $r_{\rm h, Tri~II} = 21\pm4$ pc. The properties of both systems are consistent with observe…
The relationship between quasars and their host galaxies provides clues on how supermassive black holes (SMBHs) and massive galaxies are jointly assembled. To elucidate this connection, we measure the structural and photometric properties of the host galaxies of ~5000 SDSS quasars at 0.2<z<1 using five-band (grizy) optical imaging from the Hyper Suprime-Cam Subaru Strategic Program. An automated analysis tool is used to forward-model the blended emission of the quasar as characterized by the point spread function and the underlying host galaxy as a two-dimensional Sersic profile. In agreement …
We derive distance, density and metallicity distribution of the stellar Monoceros Overdensity (MO) in the outer Milky Way, based on deep imaging with the Subaru Telescope. We applied CMD fitting techniques in three stripes at galactic longitudes: l=130 deg, 150 deg, 170 deg; and galactic latitudes: +15 < b [deg] < +25 . The MO appears as a wall of stars at a heliocentric distance of ~ 10.1\pm0.5 kpc across the observed longitude range with no distance change. The MO stars are more metal rich ([Fe/H] ~ -1.0) than the nearby stars at the same latitude. These data are used to test three different…
We present the results from a search for new Milky Way (MW) satellites from the first two years of data from the Hyper Suprime-Cam (HSC) Subaru Strategic Program (SSP) $\sim 300$~deg$^2$ and report the discovery of a highly compelling ultra-faint dwarf galaxy candidate in Cetus. This is the second ultra-faint dwarf we have discovered after Virgo~I reported in our previous paper. This satellite, Cetus~III, has been identified as a statistically significant (10.7$σ$) spatial overdensity of star-like objects, which are selected from a relevant isochrone filter designed for a metal-poor and old st…
The survey of Lyman $α$ emitters (LAEs) with Subaru Hyper Suprime-Cam, called SILVERRUSH (Ouchi et al.), is producing massive data of LAEs at $z\gtrsim6$. Here we present LAE simulations to compare the SILVERRUSH data. In 162$^3$ comoving Mpc$^3$ boxes, where numerical radiative transfer calculations of reionization were performed, LAEs have been modeled with physically motivated analytic recipes as a function of halo mass. We have examined $2^3$ models depending on the presence or absence of dispersion of halo Ly$α$ emissivity, dispersion of the halo Ly$α$ optical depth, $τ_α$, and halo mass …
We increase the sample of ultra diffuse galaxies (UDGs) in lower density environments with characterized globular cluster (GC) populations using new Hubble Space Telescope observations of nine UDGs in group environments. While the bulk of our UDGs have GC abundances consistent with normal dwarf galaxies, two of these UDGs have excess GC populations. These two UDGs both have GC luminosity functions consistent with higher surface brightness galaxies and cluster UDGs. We then combine our nine objects with previous studies to create a catalog of UDGs with analyzed GC populations that spans a uniqu…
We present the launch of the Hyper Suprime-Cam Legacy Archive (HSCLA), a public archive of processed, science-ready data from Hyper Suprime-Cam (HSC). HSC is an optical wide-field imager installed at the prime focus of the Subaru Telescope and has been in operation since 2014. While ~1/3 of the total observing time of HSC has been used for the Subaru Strategic Program (SSP), the remainder of the time is used for PI programs. We have processed the data from these PI programs and make the processed, high quality data available to the community through HSCLA. The current version of HSCLA includes…
We present an overview of a deep transient survey of the COSMOS field with the Subaru Hyper Suprime-Cam (HSC). The survey was performed for the 1.77 deg$^2$ ultra-deep layer and 5.78 deg$^2$ deep layer in the Subaru Strategic Program over 6- and 4-month periods from 2016 to 2017, respectively. The ultra-deep layer shows a median depth per epoch of 26.4, 26.3, 26.0, 25.6, and 24.6 mag in $g$, $r$, $i$, $z$, and $y$ bands, respectively; the deep layer is $\sim0.6$ mag shallower. In total, 1,824 supernova candidates were identified. Based on light curve fitting and derived light curve shape param…
The unique combination of superb spatial resolution, wide-area coverage, and deep depth of the optical imaging from the Hyper Suprime-Cam (HSC) Subaru Strategic Program is utilized to search for dual quasar candidates. Using an automated image analysis routine on 34,476 known SDSS quasars, we identify those with two (or more) distinct optical point sources in HSC images covering 796 deg^2. We find 421 candidates out to a redshift of 4.5 of which one hundred or so are more likely after filtering out contaminating stars. Angular separations of 0.6 - 4.0" correspond to projected separations of 3 …
We perform a stacking analysis of {\it Planck}, {\it AKARI}, Infrared Astronomical Satellite ($IRAS$), Wide-field Infrared Survey Eplorer ($WISE$), and {\it Herschel} images of the largest number of (candidate) protoclusters at $z\sim3.8$ selected from the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP). Stacking the images of the $179$ candidate protoclusters, the combined infrared (IR) emission of the protocluster galaxies in the observed $12-850~μ$m wavelength range is successfully detected with $>5σ$ significance (at $Planck$). This is the first time that the average IR spectral energ…
We present the luminosity function of z=4 quasars based on the Hyper Suprime-Cam Subaru Strategic Program Wide layer imaging data in the g, r, i, z, and y bands covering 339.8 deg^2. From stellar objects, 1666 z~4 quasar candidates are selected by the g-dropout selection down to i=24.0 mag. Their photometric redshifts cover the redshift range between 3.6 and 4.3 with an average of 3.9. In combination with the quasar sample from the Sloan Digital Sky Survey in the same redshift range, the quasar luminosity function covering the wide luminosity range of M1450=-22 to -29 mag is constructed. It is…
