Publications

2023

2023

1. ApJ

   Galaxy Clustering in the Mira-Titan Universe. I. Emulators for the Redshift Space Galaxy Correlation Function and Galaxy-Galaxy Lensing

   Juliana Kwan, Shun Saito, Alexie Leauthaud, and 7 more authors

   ApJ, Jul 2023
2. arXiv

   PROVABGS: The Probabilistic Stellar Mass Function of the BGS One-Percent Survey

   ChangHoon Hahn, Jessica Nicole Aguilar, Shadab Alam, and 33 more authors

   arXiv, Jun 2023
3. arXiv

   The Merian Survey: Design, Construction, and Characterization of a Filter Set Optimized to Find Dwarf Galaxies and Measure their Dark Matter Halo Properties with Weak Lensing

   Yifei Luo, Alexie Leauthaud, Jenny Greene, and 28 more authors

   arXiv, May 2023
4. arXiv

   Cluster Cosmology Without Cluster Finding

   Enia Xhakaj, Alexie Leauthaud, Johannes Lange, and 5 more authors

   arXiv, May 2023
5. MNRAS

   The contribution of in situ and ex situ star formation in early-type galaxies: MaNGA versus IllustrisTNG

   Carlo Cannarozzo, Alexie Leauthaud, Grecco A. Oyarzún, and 6 more authors

   MNRAS, Apr 2023
6. arXiv

   Beyond Ultra-Diffuse Galaxies II: Environmental Quenching of Mass-Size Outliers Among the Satellites of Milky Way Analogs

   Jiaxuan Li, Jenny E. Greene, Johnny Greco, and 5 more authors

   arXiv, Feb 2023
7. MNRAS

   Consistent lensing and clustering in a low-S_8 Universe with BOSS, DES Year 3, HSC Year 1, and KiDS-1000

   A. Amon, N. C. Robertson, H. Miyatake, and 105 more authors

   MNRAS, Jan 2023

2022

2022

1. ApJ

   Ultra-diffuse Galaxies as Extreme Star-forming Environments. I. Mapping Star Formation in H I-rich UDGs

   Erin Kado-Fong, Jenny E. Greene, Song Huang, and 1 more author

   ApJ, Dec 2022
2. arXiv

   Beyond Ultra-Diffuse Galaxies I: Mass-Size Outliers Among the Satellites of Milky Way Analogs

   Jiaxuan Li, Jenny E. Greene, Johnny P. Greco, and 10 more authors

   arXiv, Oct 2022
3. MNRAS

   Reaching for the Edge I: probing the outskirts of massive galaxies with HSC, DECaLS, SDSS, and Dragonfly

   Jiaxuan Li, Song Huang, Alexie Leauthaud, and 9 more authors

   MNRAS, Oct 2022

   Abs HTML PDF

   The outer light (stellar haloes) of massive galaxies has recently emerged as a possible low scatter tracer of dark matter halo mass. To test the robustness of outer light measurements across different data sets, we compare the 1D azimuthally averaged surface brightness profiles of massive galaxies using four independent data sets: the Hyper Suprime-Cam survey (HSC), the Dark Energy Camera Legacy Survey (DECaLS), the Sloan Digital Sky Survey (SDSS), and the Dragonfly Wide Field Survey (Dragonfly). We test the sky subtraction and proposed corrections for HSC and DECaLS. For galaxies at z < 0.05, Dragonfly has the best control of systematics, reaching surface brightness levels of μr ≈ 30 mag arcsec-2. At 0.19 < z < 0.50, HSC can reliably recover individual surface brightness profiles to μr ≈ 28.5 mag arcsec-2 (R = 100-150 kpc in semimajor axis). In a statistical sense, DECaLS agrees with HSC to R > 200 kpc. DECaLS and HSC measurements of the stellar mass contained within 100 kpc agree within 0.05 dex. Finally, we use weak lensing to show that measurements of outer light with DECaLS at 0.19 < z < 0.50 show a similar promise as HSC as a low scatter proxy of halo mass. The tests and results from this paper represent an important step forward for accurate measurements of the outer light of massive galaxies and demonstrate that outer light measurements from DECam imaging will be a promising method for finding galaxy clusters.

4. MNRAS

   The outer stellar mass of massive galaxies: a simple tracer of halo mass with scatter comparable to richness and reduced projection effects

   Song Huang, Alexie Leauthaud, Christopher Bradshaw, and 7 more authors

   MNRAS, Oct 2022

   Abs HTML PDF Code

   Using the weak gravitational lensing data from the Hyper Suprime-Cam Subaru Strategic Program (HSC survey), we study the potential of different stellar mass estimates in tracing halo mass. We consider galaxies with log10(M⋆/M⊙) > 11.5 at 0.2 < z < 0.5 with carefully measured light profiles, and clusters from the redMaPPer and CAMIRA richness-based algorithms. We devise a method (the ’Top-N test’) to evaluate the scatter in the halo mass-observable relation for different tracers, and to inter-compare halo mass proxies in four number density bins using stacked galaxy-galaxy lensing profiles. This test reveals three key findings. Stellar masses based on CModel photometry and aperture luminosity within R <30 kpc are poor proxies of halo mass. In contrast, the stellar mass of the outer envelope is an excellent halo mass proxy. The stellar mass within R = [50, 100] kpc, M⋆, [50, 100], has performance comparable to the state-of-the-art richness-based cluster finders at log10Mvir ≳ 14.0 and could be a better halo mass tracer at lower halo masses. Finally, using N-body simulations, we find that the lensing profiles of massive haloes selected by M⋆, [50, 100] are consistent with the expectation for a sample without projection or mis-centring effects. Richness-selected clusters, on the other hand, display an excess at R   1 Mpc in their lensing profiles, which may suggest a more significant impact from selection biases. These results suggest that M⋆-based tracers have distinct advantages in identifying massive haloes, which could open up new avenues for cluster cosmology.

5. ApJ

   The Nature of Low-surface-brightness Galaxies in the Hyper Suprime-Cam Survey

   Jenny E. Greene, Johnny P. Greco, Andy D. Goulding, and 9 more authors

   ApJ, Jul 2022
6. ApJ

   SDSS-IV MaNGA: Cannibalism Caught in the Act-On the Frequency of Occurrence of Multiple Cores in Brightest Cluster Galaxies

   Yun-Hsin Hsu, Yen-Ting Lin, Song Huang, and 16 more authors

   ApJ, Jul 2022
7. ApJ

   The In Situ Origins of Dwarf Stellar Outskirts in FIRE-2

   Erin Kado-Fong, Robyn E. Sanderson, Jenny E. Greene, and 11 more authors

   ApJ, Jun 2022
8. MNRAS

   Lensing without borders - I. A blind comparison of the amplitude of galaxy-galaxy lensing between independent imaging surveys

   A. Leauthaud, A. Amon, S. Singh, and 104 more authors

   MNRAS, Mar 2022
9. MNRAS

   Ultra-diffuse galaxies in the perseus cluster: comparing galaxy properties with globular cluster system richness

   Jonah S. Gannon, Duncan A. Forbes, Aaron J. Romanowsky, and 6 more authors

   MNRAS, Feb 2022

2021

2021

1. MNRAS

   Anomaly detection in Hyper Suprime-Cam galaxy images with generative adversarial networks

   Kate Storey-Fisher, Marc Huertas-Company, Nesar Ramachandra, and 5 more authors

   MNRAS, Dec 2021
2. ApJ

   Hyper Suprime-Cam Subaru Strategic Program: A Mass-dependent Slope of the Galaxy Size-Mass Relation at z < 1

   Lalitwadee Kawinwanichakij, John D. Silverman, Xuheng Ding, and 11 more authors

   ApJ, Nov 2021
3. MNRAS

   Brightest cluster galaxies are statistically special from z = 0.3 to z = 1

   Roohi Dalal, Michael A. Strauss, Tomomi Sunayama, and 5 more authors

   MNRAS, Nov 2021
4. ApJ

   The Intrinsic Shapes of Low Surface Brightness Galaxies (LSBGs): A Discriminant of LSBG Galaxy Formation Mechanisms

   Erin Kado-Fong, Mihai Petrescu, Majid Mohammad, and 8 more authors

   ApJ, Oct 2021
5. ApJ

   A Search for Wandering Black Holes in the Milky Way with Gaia and DECaLS

   Jenny E. Greene, Lachlan Lancaster, Yuan-Sen Ting, and 6 more authors

   ApJ, Aug 2021
6. MNRAS

   Stellar and weak lensing profiles of massive galaxies in the Hyper-Suprime Cam survey and in hydrodynamic simulations

   Felipe Ardila, Song Huang, Alexie Leauthaud, and 11 more authors

   MNRAS, Jan 2021

2020

2020

1. MNRAS

   How accurately can we detect the splashback radius of dark matter haloes and its correlation with accretion rate?

   Enia Xhakaj, Benedikt Diemer, Alexie Leauthaud, and 5 more authors

   MNRAS, Dec 2020
2. arXiv

   Anomaly Detection in Astronomical Images with Generative Adversarial Networks

   Kate Storey-Fisher, Marc Huertas-Company, Nesar Ramachandra, and 4 more authors

   arXiv e-prints, Dec 2020
3. ApJ

   SDSS-IV MaNGA: The Nature of an Off-galaxy H_\ensuremathα Blob—A Multiwavelength View of Offset Cooling in a Merging Galaxy Group

   Hsi-An Pan, Lihwai Lin, Bau-Ching Hsieh, and 20 more authors

   ApJ, Nov 2020
4. ApJ

   Hyper Suprime-Cam Low Surface Brightness Galaxies. II. A Hubble Space Telescope Study of the Globular Cluster Systems of Ultradiffuse Galaxies in Groups

   Jean J. Somalwar, Jenny E. Greene, Johnny P. Greco, and 4 more authors

   ApJ, Oct 2020
5. ApJ

   Tracing the Intrinsic Shapes of Dwarf Galaxies Out to Four Effective Radii: Clues to Low-mass Stellar Halo Formation

   Erin Kado-Fong, Jenny E. Greene, Song Huang, and 3 more authors

   ApJ, Sep 2020
6. MNRAS

   Weak lensing reveals a tight connection between dark matter halo mass and the distribution of stellar mass in massive galaxies

   Song Huang, Alexie Leauthaud, Andrew Hearin, and 9 more authors

   MNRAS, Mar 2020

   Abs HTML PDF Code

   Using deep images from the Hyper Suprime-Cam (HSC) survey and taking advantage of its unprecedented weak lensing capabilities, we reveal a remarkably tight connection between the stellar mass distribution of massive central galaxies and their host dark matter halo mass. Massive galaxies with more extended stellar mass distributions tend to live in more massive dark matter haloes. We explain this connection with a phenomenological model that assumes, (1) a tight relation between the halo mass and the total stellar content in the halo, (2) that the fraction of in situ and ex situ mass at r <10 kpc depends on halo mass. This model provides an excellent description of the stellar mass functions (SMFs) of total stellar mass (M_⋆^max) and stellar mass within inner 10 kpc (M_⋆^10) and also reproduces the HSC weak lensing signals of massive galaxies with different stellar mass distributions. The best-fitting model shows that halo mass varies significantly at fixed total stellar mass (as much as 0.4 dex) with a clear dependence on M_⋆^10. Our two-parameter M_⋆^max-M_⋆^10 description provides a more accurate picture of the galaxy-halo connection at the high-mass end than the simple stellar-halo mass relation (SHMR) and opens a new window to connect the assembly history of haloes with those of central galaxies. The model also predicts that the ex situ component dominates the mass profiles of galaxies at r < 10 kpc for log M⋆ ≥ 11.7.

7. MNRAS

   Physical correlations of the scatter between galaxy mass, stellar content, and halo mass

   Christopher Bradshaw, Alexie Leauthaud, Andrew Hearin, and 2 more authors

   MNRAS, Mar 2020

   Abs HTML PDF

   We use the UniverseMachine to analyse the source of scatter between the central galaxy mass, the total stellar mass in the halo, and the dark matter halo mass, for massive (Mvir > 1013 M⊙) haloes. We also propose a new halo mass estimator, the cen+N mass: the sum of the stellar mass of the central and the N most massive satellites. We show that, when real space positions are perfectly known, the cen+N mass has scatter competitive with that of richness-based estimators. However, in redshift space, using a simple cluster finder, the cen+N mass suffers less from projection effects in the UniverseMachine model. The cen+N mass is therefore a potential candidate to constrain cosmology with upcoming spectroscopic data from DESI. We analyse the scatter in stellar mass at fixed halo mass and show that the total stellar mass in a halo is uncorrelated with secondary halo properties, but that the central stellar mass is a function of both halo mass and halo age. This is because central galaxies in older haloes have had more time to grow via accretion. If the UniverseMachine model is correct, this implies that haloes selected using the centrals stellar mass will be biased old and that accurate galaxy-halo modelling of mass selected samples therefore needs to consider halo age in addition to mass.

2019

2019

1. MNRAS

   Galaxy-Galaxy lensing in HSC: Validation tests and the impact of heterogeneous spectroscopic training sets

   Joshua S. Speagle, Alexie Leauthaud, Song Huang, and 9 more authors

   MNRAS, Dec 2019
2. PASJ

   Second data release of the Hyper Suprime-Cam Subaru Strategic Program

   Hiroaki Aihara, Yusra AlSayyad, Makoto Ando, and 62 more authors

   PASJ, Dec 2019
3. MNRAS

   The stellar halo of isolated central galaxies in the Hyper Suprime-Cam imaging survey

   Wenting Wang, Jiaxin Han, Alessandro Sonnenfeld, and 14 more authors

   MNRAS, Aug 2019
4. ApJ

   The Brightest UV-selected Galaxies in Protoclusters at z \ensuremath∼ 4: Ancestors of Brightest Cluster Galaxies?

   Kei Ito, Nobunari Kashikawa, Jun Toshikawa, and 13 more authors

   ApJ, Jun 2019

2018

2018

1. ApJ

   Tidal Features at 0.05 < z < 0.45 in the Hyper Suprime-Cam Subaru Strategic Program: Properties and Formation Channels

   E. Kado-Fong, J. E. Greene, D. Hendel, and 10 more authors

   ApJ, Oct 2018
2. MNRAS

   A detection of the environmental dependence of the sizes and stellar haloes of massive central galaxies

   Song Huang, Alexie Leauthaud, Jenny Greene, and 6 more authors

   MNRAS, Oct 2018

   Abs HTML PDF

   We use ∼100 deg2 of deep (>28.5 mag arcsec-2 in i band), high-quality (median 0.6 arcsec seeing) imaging data from the Hyper Suprime-Cam (HSC) survey to reveal the halo mass dependence of the surface mass density profiles and outer stellar envelopes of massive galaxies. The i-band images from the HSC survey reach ∼4 mag deeper than Sloan Digital Sky Survey and enable us to directly trace stellar mass distributions to 100 kpc without requiring stacking. We conclusively show that, at fixed stellar mass, the stellar profiles of massive galaxies depend on the masses of their dark matter haloes. On average, massive central galaxies with log10(M⋆, 100 kpc/M⊙)>11.6 in more massive haloes at 0.3 < z < 0.5 have shallower inner stellar mass density profiles (within ∼10-20 kpc) and more prominent outer envelopes. These differences translate into a halo mass dependence of the mass-size relation. Central galaxies in haloes with log10(M200b/M⊙)>14.0 are ∼20 per cent larger in R50 at fixed M⋆, 100 kpc. Such dependence is also reflected in the relationship between the stellar mass within 10 and 100 kpc. Comparing to the mass-size relation, the M⋆, 100 kpc-M⋆, 10 kpc relation avoids the ambiguity in the definition of size, and can be straightforwardly compared with simulations. Our results demonstrate that, with deep images from HSC, we can quantify the connection between halo mass and the outer stellar halo, which may provide new constraints on the formation and assembly of massive central galaxies.

3. ApJ

   A Study of Two Diffuse Dwarf Galaxies in the Field

   Johnny P. Greco, Andy D. Goulding, Jenny E. Greene, and 4 more authors

   ApJ, Oct 2018
4. MNRAS

   Imaging extended emission-line regions of obscured AGN with the Subaru Hyper Suprime-Cam Survey

   Ai-Lei Sun, Jenny E. Greene, Nadia L. Zakamska, and 9 more authors

   MNRAS, Oct 2018
5. ApJ

   Illuminating Low Surface Brightness Galaxies with the Hyper Suprime-Cam Survey

   Johnny P. Greco, Jenny E. Greene, Michael A. Strauss, and 11 more authors

   ApJ, Apr 2018
6. MNRAS

   Individual stellar haloes of massive galaxies measured to 100 kpc at 0.3 < z < 0.5 using Hyper Suprime-Cam

   Song Huang, Alexie Leauthaud, Jenny E. Greene, and 5 more authors

   MNRAS, Apr 2018

   Abs HTML PDF

   Massive galaxies display extended light profiles that can reach several hundreds of kiloparsecs. We use data from the Hyper Suprime-Cam (HSC) survey that is simultaneously wide (∼100 deg2) and deep (>28.5 mag arcsec-2 in i band) to study the stellar haloes of a sample of ∼7000 massive galaxies at z ∼ 0.4. The depth of the HSC data enables us to measure surface mass density profiles to 100 kpc for individual galaxies without stacking. As in previous work, we find that more massive galaxies exhibit more extended outer profiles than smaller galaxies. When this extended light is not properly accounted for (because of shallow imaging and/or inadequate profile modelling), the derived stellar mass function can be significantly underestimated at the high-mass end. Across our sample, the ellipticity of outer light profile increases substantially with radius. We show for the first time that these ellipticity gradients steepen dramatically as a function of galaxy mass, but we detect no mass dependence in outer colour gradients. Our results support the two-phase formation scenario for massive galaxies in which outer envelopes are built up at a later time from a series of merging events. We provide surface mass density profiles in a convenient tabulated format to facilitate comparisons with predictions from numerical simulations of galaxy formation.

7. PASJ

   Source selection for cluster weak lensing measurements in the Hyper Suprime-Cam survey

   Elinor Medezinski, Masamune Oguri, Atsushi J. Nishizawa, and 13 more authors

   PASJ, Mar 2018
8. PASJ

   First results on the cluster galaxy population from the Subaru Hyper Suprime-Cam survey. II. Faint end color-magnitude diagrams and radial profiles of red and blue galaxies at 0.1 < z < 1.1

   Atsushi J. Nishizawa, Masamune Oguri, Taira Oogi, and 16 more authors

   PASJ, Jan 2018
9. PASJ

   Sumo Puff: Tidal debris or disturbed ultra-diffuse galaxy?

   Johnny P. Greco, Jenny E. Greene, Adrian M. Price-Whelan, and 10 more authors

   PASJ, Jan 2018
10. PASJ

    First data release of the Hyper Suprime-Cam Subaru Strategic Program

    Hiroaki Aihara, Robert Armstrong, Steven Bickerton, and 107 more authors

    PASJ, Jan 2018
11. Characterization and photometric performance of the Hyper Suprime-Cam Software Pipeline

    Song Huang, Alexie Leauthaud, Ryoma Murata, and 9 more authors

    PASJ, Jan 2018

    Abs HTML PDF

    The Subaru Strategic Program (SSP) is an ambitious multi-band survey using the Hyper Suprime-Cam (HSC) on the Subaru telescope. The Wide layer of the SSP is both wide and deep, reaching a detection limit of i ∼ 26.0 mag. At these depths, it is challenging to achieve accurate, unbiased, and consistent photometry across all five bands. The HSC data are reduced using a pipeline that builds on the prototype pipeline for the Large Synoptic Survey Telescope. We have developed a Python-based, flexible framework to inject synthetic galaxies into real HSC images, called SynPipe. Here we explain the design and implementation of SynPipe and generate a sample of synthetic galaxies to examine the photometric performance of the HSC pipeline. For stars, we achieve 1% photometric precision at i ∼ 19.0 mag and 6% precision at i ∼ 25.0 in the i band (corresponding to statistical scatters of ∼0.01 and ∼0.06 mag respectively). For synthetic galaxies with single-Sérsic profiles, forced CModel photometry achieves 13% photometric precision at i ∼ 20.0 mag and 18% precision at i ∼ 25.0 in the i band (corresponding to statistical scatters of ∼0.15 and ∼0.22 mag respectively). We show that both forced point spread function and CModel photometry yield unbiased color estimates that are robust to seeing conditions. We identify several caveats that apply to the version of HSC pipeline used for the first public HSC data release (DR1) that need to be taking into consideration. First, the degree to which an object is blended with other objects impacts the overall photometric performance. This is especially true for point sources. Highly blended objects tend to have larger photometric uncertainties, systematically underestimated fluxes, and slightly biased colors. Secondly, >20% of stars at 22.5 < i < 25.0 mag can be misclassified as extended objects. Thirdly, the current CModel algorithm tends to strongly underestimate the half-light radius and ellipticity of galaxy with i > 21.5 mag.

12. PASJ

    The Hyper Suprime-Cam software pipeline

    James Bosch, Robert Armstrong, Steven Bickerton, and 32 more authors

    PASJ, Jan 2018
13. PASJ

    The first-year shear catalog of the Subaru Hyper Suprime-Cam Subaru Strategic Program Survey

    Rachel Mandelbaum, Hironao Miyatake, Takashi Hamana, and 28 more authors

    PASJ, Jan 2018
14. PASJ

    The Hyper Suprime-Cam SSP Survey: Overview and survey design

    Hiroaki Aihara, Nobuo Arimoto, Robert Armstrong, and 141 more authors

    PASJ, Jan 2018

2017

2017

1. ApJ

   First Results on the Cluster Galaxy Population from the Subaru Hyper Suprime-Cam Survey. III. Brightest Cluster Galaxies, Stellar Mass Distribution, and Active Galaxies

   Yen-Ting Lin, Bau-Ching Hsieh, Sheng-Chieh Lin, and 12 more authors

   ApJ, Dec 2017
2. ApJ

   SDSS IV MaNGA: Discovery of an H\ensuremathα Blob Associated with a Dry Galaxy Pair—Ejected Gas or a “Dark” Galaxy Candidate?

   Lihwai Lin, Jing-Hua Lin, Chin-Hao Hsu, and 31 more authors

   ApJ, Mar 2017

2016

2016

1. ApJ

   SDSS-IV MaNGA: A Serendipitous Observation of a Potential Gas Accretion Event

   Edmond Cheung, David V. Stark, Song Huang, and 24 more authors

   ApJ, Dec 2016
2. MNRAS

   SDSS-IV MaNGA: properties of galaxies with kinematically decoupled stellar and gaseous components

   Yifei Jin, Yanmei Chen, Yong Shi, and 30 more authors

   MNRAS, Nov 2016
3. NatCo

   The growth of the central region by acquisition of counterrotating gas in star-forming galaxies

   Yan-Mei Chen, Yong Shi, Christy A. Tremonti, and 29 more authors

   Nature Communications, Oct 2016
4. ApJ

   The Carnegie-Irvine Galaxy Survey. IV. A Method to Determine the Average Mass Ratio of Mergers That Built Massive Elliptical Galaxies

   Song Huang, Luis C. Ho, Chien Y. Peng, and 2 more authors

   ApJ, Apr 2016
5. MNRAS

   The Stripe 82 Massive Galaxy Project - II. Stellar mass completeness of spectroscopic galaxy samples from the Baryon Oscillation Spectroscopic Survey

   Alexie Leauthaud, Kevin Bundy, Shun Saito, and 7 more authors

   MNRAS, Apr 2016

2014

2014

1. ApJ

   Color-Magnitude Distribution of Face-on nearby Galaxies in Sloan Digital Sky Survey DR7

   Shuo-Wen Jin, Qiusheng Gu, Song Huang, and 2 more authors

   ApJ, May 2014
2. ApJ

   How Robust are the Size Measurements of High-redshift Compact Galaxies?

   Roozbeh Davari, Luis C. Ho, Chien Y. Peng, and 1 more author

   ApJ, May 2014

2013

2013

1. ApJ

   A Novel Approach to Constrain the Mass Ratio of Minor Mergers in Elliptical Galaxies: Application to NGC 4889, the Brightest Cluster Galaxy in Coma

   Meng Gu, Luis C. Ho, Chien Y. Peng, and 1 more author

   ApJ, Aug 2013
2. ApJL

   Fossil Evidence for the Two-phase Formation of Elliptical Galaxies

   Song Huang, Luis C. Ho, Chien Y. Peng, and 2 more authors

   ApJl, May 2013

   Abs HTML PDF

   Massive early-type galaxies (ETGs) have undergone dramatic structural evolution over the last 10 Gyr. A companion paper shows that nearby elliptical galaxies with M * >= 1.3 × 1011 M ⊙ generically contain three photometric subcomponents: a compact inner component with effective radius Re <  1 kpc, an intermediate-scale middle component with Re ≈ 2.5 kpc, and an extended outer envelope with Re ≈ 10 kpc. Here we attempt to relate these substructures with the properties of ETGs observed at higher redshifts. We find that a hypothetical structure formed from combining the inner and middle components of local ellipticals follows a strikingly tight stellar mass-size relation, one that resembles the distribution of ETGs at z ≈ 1. Outside of the central kpc, the median stellar mass surface density profiles of this composite structure agree closest with those of massive galaxies that have similar cumulative number density at 1.5 < z < 2.0 within the uncertainty. We propose that the central substructures in nearby ellipticals are the evolutionary descendants of the "red nuggets" formed under highly dissipative ("wet") conditions at high redshifts, as envisioned in the initial stages of the two-phase formation scenario recently advocated for massive galaxies. Subsequent accretion, plausibly through dissipationless ("dry") minor mergers, builds the outer regions of the galaxy identified as the outer envelope in our decomposition. The large scatter exhibited by this component on the stellar mass-size plane testifies to the stochastic nature of the accretion events.

3. ApJ

   The Carnegie-Irvine Galaxy Survey. III. The Three-component Structure of Nearby Elliptical Galaxies

   Song Huang, Luis C. Ho, Chien Y. Peng, and 2 more authors

   ApJ, Mar 2013

   Abs HTML PDF

   Motivated by recent developments in our understanding of the formation and evolution of massive galaxies, we explore the detailed photometric structure of a representative sample of 94 bright, nearby elliptical galaxies, using high-quality optical images from the Carnegie-Irvine Galaxy Survey. The sample spans a range of environments and stellar masses, from M * = 1010.2 to 1012.0 M ⊙. We exploit the unique capabilities of two-dimensional image decomposition to explore the possibility that local elliptical galaxies may contain photometrically distinct substructure that can shed light on their evolutionary history. Compared with the traditional one-dimensional approach, these two-dimensional models are capable of consistently recovering the surface brightness distribution and the systematic radial variation of geometric information at the same time. Contrary to conventional perception, we find that the global light distribution of the majority (>75%) of elliptical galaxies is not well described by a single Sérsic function. Instead, we propose that local elliptical galaxies generically contain three subcomponents: a compact (Re <  1 kpc) inner component with luminosity fraction f ≈ 0.1-0.15; an intermediate-scale (Re ≈ 2.5 kpc) middle component with f ≈ 0.2-0.25; and a dominant (f = 0.6), extended (Re ≈ 10 kpc) outer envelope. All subcomponents have average Sérsic indices n ≈ 1-2, significantly lower than the values typically obtained from single-component fits. The individual subcomponents follow well-defined photometric scaling relations and the stellar mass-size relation. We discuss the physical nature of the substructures and their implications for the formation of massive elliptical galaxies.

2009

2009

1. RAA

   Stellar ages and metallicities of nearby elliptical galaxies

   Bai-Tian Tang, Qiu-Sheng Gu, and Song Huang

   Research in Astronomy and Astrophysics, Nov 2009
2. MNRAS

   Recent star-forming activity in local elliptical galaxies

   Song Huang, and Q. -S. Gu

   MNRAS, Oct 2009