ORCID Profile
0000-0001-5063-8254
Current Organisations
University of Pittsburgh
,
University of Arizona Department of Astronomy and Steward Observatory
,
Poly Prep Country Day School
,
Barnard College
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In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Astronomical sciences | Sensory Processes, Perception and Performance | Psychology | Cosmology and extragalactic astronomy | Behavioural Ecology |
Expanding Knowledge in the Biological Sciences | Expanding Knowledge in Psychology and Cognitive Sciences | Expanding Knowledge in Technology |
Publisher: American Astronomical Society
Date: 28-09-2022
Abstract: Galaxy sizes and their evolution over cosmic time have been studied for decades and serve as key tests of galaxy formation models. However, at z ≳ 1 these studies have been limited by a lack of deep, high-resolution rest-frame infrared imaging that accurately traces stellar mass distributions. Here, we leverage the new capabilities of the James Webb Space Telescope (JWST) to measure the 4.4 μ m sizes of ∼1000 galaxies with log M * / M ⊙ ≥ 9 and 1.0 ≤ z ≤ 2.5 from public CEERS imaging in the Extended Groth Strip deep field. We compare the sizes of galaxies measured from NIRCam imaging at 4.4 μ m ( λ rest ∼ 1.6 μ m) with sizes measured at 1.5 μ m ( λ rest ∼ 5500 Å). We find that, on average, galaxy half-light radii are ∼9% smaller at 4.4 μ m than 1.5 μ m in this s le. This size difference is markedly stronger at higher stellar masses and redder rest-frame V − J colors: galaxies with M * ∼ 10 11 M ⊙ have 4.4 μ m sizes that are ∼30% smaller than their 1.5 μ m sizes. Our results indicate that galaxy mass profiles are significantly more compact than their rest-frame optical light profiles at cosmic noon, and demonstrate that spatial variations in age and attenuation are important, particularly for massive galaxies. The trend we find here impacts our understanding of the size growth and evolution of galaxies, and suggests that previous studies based on rest-frame optical light may not have captured the mass-weighted structural evolution of galaxies. This paper represents a first step toward a new understanding of the morphologies of early massive galaxies enabled by JWST’s infrared window into the distant universe.
Publisher: American Astronomical Society
Date: 05-2023
Abstract: With just a month of data, JWST is already transforming our view of the universe, revealing and resolving starlight in unprecedented populations of galaxies. Although “HST-dark” galaxies have previously been detected at long wavelengths, these observations generally suffer from a lack of spatial resolution, which limits our ability to characterize their sizes and morphologies. Here we report on a first view of starlight from a subset of the HST-dark population that is bright with JWST/NIRCam (4.4 μ m 24.5 mag) and very faint or even invisible with HST ( .6 μ m). In this Letter we focus on a dramatic and unanticipated population of physically extended galaxies (≳0.″25). These 12 galaxies have photometric redshifts 2 z 6, high stellar masses M ⋆ ≳ 10 10 M ⊙ , and significant dust-attenuated star formation. Surprisingly, the galaxies have elongated projected axis ratios at 4.4 μ m, suggesting that the population is disk dominated or prolate and we hence refer to them as ultrared flattened objects. Most of the galaxies appear red at all radii, suggesting significant dust attenuation throughout. With R e (F444W) ∼ 1–2 kpc, the galaxies are similar in size to compact massive galaxies at z ∼ 2 and the cores of massive galaxies and S0s at z ∼ 0. The stellar masses, sizes, and morphologies of the s le suggest that some could be progenitors of lenticular or fast-rotating galaxies in the local universe. The existence of this population suggests that our previous censuses of the universe may have missed massive, dusty edge-on disks, in addition to dust-obscured starbursts.
Publisher: American Astronomical Society
Date: 29-11-2018
Publisher: American Astronomical Society
Date: 02-2023
Abstract: The advent of the James Webb Space Telescope (JWST) signals a new era in exploring galaxies in the high- z universe. Current and upcoming JWST imaging will potentially detect galaxies at z ∼ 20, creating a new urgency in the quest to infer accurate photometric redshifts (photo- z ) for in idual galaxies from their spectral energy distributions, as well as masses, ages, and star formation rates. Here we illustrate the utility of informed priors encoding previous observations of galaxies across cosmic time in achieving these goals. We construct three joint priors encoding empirical constraints of redshifts, masses, and star formation histories in the galaxy population within the Prospector Bayesian inference framework. In contrast with uniform priors, our model breaks an age–mass–redshift degeneracy, and thus reduces the mean bias error in masses from 0.3 to 0.1 dex, and in ages from 0.6 to 0.2 dex in tests done on mock JWST observations. Notably, our model recovers redshifts at least as accurately as the state-of-the-art photo- z code EAzY in deep JWST fields, but with two advantages: tailoring a model based on a particular survey is rendered mostly unnecessary given well-motivated priors obtaining joint posteriors describing stellar, active galactic nuclei, gas, and dust contributions becomes possible. We can now confidently use the joint distribution to propagate full non-Gaussian redshift uncertainties into inferred properties of the galaxy population. This model, “ Prospector - β ,” is intended for fitting galaxy photometry where the redshift is unknown, and will be instrumental in ensuring the maximum science return from forthcoming photometric surveys with JWST. The code is made publicly available online as a part of Prospector 9 9 The version used in this work corresponds to the state of the Git repository at commit d-j rospector/commit/820ad72363a1f9c22cf03610bfe6e361213385cd . .
Publisher: American Astronomical Society
Date: 02-11-2012
Publisher: American Astronomical Society
Date: 21-09-2017
Publisher: American Astronomical Society
Date: 20-02-2020
Publisher: Oxford University Press (OUP)
Date: 21-08-2023
Publisher: American Astronomical Society
Date: 06-11-2020
Publisher: Springer Science and Business Media LLC
Date: 22-02-2023
Publisher: American Astronomical Society
Date: 12-03-2018
Publisher: American Astronomical Society
Date: 21-11-2011
Publisher: American Astronomical Society
Date: 09-2023
Publisher: American Astronomical Society
Date: 25-07-2023
Abstract: Recent JWST/NIRCam imaging taken for the ultra-deep UNCOVER program reveals a very red dropout object at z phot ≃ 7.6, triply imaged by the galaxy cluster A2744 ( z d = 0.308). All three images are very compact, i.e., unresolved, with a delensed size upper limit of r e ≲ 35 pc. The images have apparent magnitudes of m F444W ∼ 25−26 AB, and the magnification-corrected absolute UV magnitude of the source is M UV,1450 = −16.81 ± 0.09. From the sum of observed fluxes and from a spectral energy distribution (SED) analysis, we obtain estimates of the bolometric luminosities of the source of L bol ≳ 10 43 erg s −1 and L bol ∼ 10 44 –10 46 erg s −1 , respectively. Based on its compact, point-like appearance, its position in color–color space, and the SED analysis, we tentatively conclude that this object is a UV-faint dust-obscured quasar-like object, i.e., an active galactic nucleus at high redshift. We also discuss other alternative origins for the object’s emission features, including a massive star cluster, Population III, supermassive, or dark stars, or a direct-collapse black hole. Although populations of red galaxies at similar photometric redshifts have been detected with JWST, this object is unique in that its high-redshift nature is corroborated geometrically by lensing, that it is unresolved despite being magnified—and thus intrinsically even more compact—and that it occupies notably distinct regions in both size–luminosity and color–color space. Planned UNCOVER JWST/NIRSpec observations, scheduled in Cycle 1, will enable a more detailed analysis of this object.
Publisher: American Astronomical Society
Date: 28-05-2021
Abstract: We explore the connection between the kinematics, structures and stellar populations of massive galaxies at 0.6 z 1.0 using the fundamental plane (FP). Combining stellar kinematic data from the Large Early Galaxy Astrophysics Census (LEGA-C) survey with structural parameters measured from deep Hubble Space Telescope imaging, we obtain a s le of 1419 massive ( log ( M * / M ⊙ ) 10.5 ) galaxies that span a wide range in morphology, star formation activity, and environment, and therefore is representative of the massive galaxy population at z ∼ 0.8. We find that quiescent and star-forming galaxies occupy the parameter space of the g -band FP differently and thus have different distributions in the dynamical mass-to-light ratio ( M dyn / L g ), largely owing to differences in the stellar age and recent star formation history, and to a lesser extent, the effects of dust attenuation. In contrast, we show that both star-forming and quiescent galaxies lie on the same mass FP at z ∼ 0.8, with a comparable level of intrinsic scatter about the plane. We examine the variation in M dyn / M * through the thickness of the mass FP, finding no significant residual correlations with stellar population properties, Sérsic index, or galaxy overdensity. Our results suggest that, at fixed size and velocity dispersion, the variations in M dyn / L g of massive galaxies reflect an approximately equal contribution of variations in M * / L g , and variations in the dark matter fraction or initial mass function.
Publisher: American Astronomical Society
Date: 12-2021
Abstract: We present spatially resolved stellar kinematics for 797 z = 0.6–1 galaxies selected from the LEGA-C survey and construct axisymmetric Jeans models to quantify their dynamical mass and degree of rotational support. The survey is K s -band selected, irrespective of color or morphological type, and allows for a first assessment of the stellar dynamical structure of the general L * galaxy population at large look-back time. Using light profiles from Hubble Space Telescope imaging as a tracer, our approach corrects for observational effects (seeing convolution and slit geometry), and uses well-informed priors on inclination, anisotropy, and a non-luminous mass component. Tabulated data include total mass estimates in a series of spherical apertures (1, 5, and 10 kpc 1 × and 2 × R e ), as well as rotational velocities, velocity dispersions, and anisotropy. We show that almost all star-forming galaxies and ∼50% of quiescent galaxies are rotation dominated, with deprojected V / σ ∼ 1–2. Revealing the complexity in galaxy evolution, we find that the most massive star-forming galaxies are among the most rotation dominated, and the most massive quiescent galaxies among the least rotation-dominated galaxies. These measurements set a new benchmark for studying galaxy evolution, using stellar dynamical structure for galaxies at large look-back time. Together with the additional information on stellar population properties from the LEGA-C spectra, the dynamical mass and V / σ measurements presented here create new avenues for studying galaxy evolution at large look-back time.
Publisher: American Astronomical Society
Date: 21-02-2012
Publisher: American Astronomical Society
Date: 09-2023
Publisher: American Astronomical Society
Date: 05-12-2018
Publisher: American Astronomical Society
Date: 11-2022
Abstract: The first few 100 Myr at z 10 mark the last major uncharted epoch in the history of the universe, where only a single galaxy (GN-z11 at z ≈ 11) is currently spectroscopically confirmed. Here we present a search for luminous z 10 galaxies with JWST/NIRCam photometry spanning ≈1–5 μ m and covering 49 arcmin 2 from the public JWST Early Release Science programs (CEERS and GLASS). Our most secure candidates are two M UV ≈ −21 systems: GLASS-z12 and GLASS-z10. These galaxies display abrupt ≳1.8 mag breaks in their spectral energy distributions (SEDs), consistent with complete absorption of flux bluewards of Ly α that is redshifted to z = 12.4 − 0.3 + 0.1 and z = 10.4 − 0.5 + 0.4 . Lower redshift interlopers such as quiescent galaxies with strong Balmer breaks would be comfortably detected at σ in multiple bands where instead we find no flux. From SED modeling we infer that these galaxies have already built up ∼10 9 solar masses in stars over the ≲300–400 Myr after the Big Bang. The brightness of these sources enable morphological constraints. Tantalizingly, GLASS-z10 shows a clearly extended exponential light profile, potentially consistent with a disk galaxy of r 50 ≈ 0.7 kpc. These sources, if confirmed, join GN-z11 in defying number density forecasts for luminous galaxies based on Schechter UV luminosity functions, which require a survey area × larger than we have studied here to find such luminous sources at such high redshifts. They extend evidence from lower redshifts for little or no evolution in the bright end of the UV luminosity function into the cosmic dawn epoch, with implications for just how early these galaxies began forming. This, in turn, suggests that future deep JWST observations may identify relatively bright galaxies to much earlier epochs than might have been anticipated.
Publisher: American Astronomical Society
Date: 18-06-2018
Publisher: American Astronomical Society
Date: 20-03-2017
Publisher: American Astronomical Society
Date: 23-03-2201
Publisher: Oxford University Press (OUP)
Date: 21-08-2023
Publisher: American Astronomical Society
Date: 22-09-2015
Publisher: American Astronomical Society
Date: 26-10-2023
Publisher: American Astronomical Society
Date: 04-05-2018
Publisher: Oxford University Press (OUP)
Date: 16-03-2022
Abstract: We investigate changes in stellar population age and metallicity ([Z/H]) scaling relations for quiescent galaxies from intermediate redshift (0.60 ≤ $z$ ≤ 0.76) using the LEGA-C Survey to low redshift (0.014 ≤ $z$ ≤ 0.10) using the SAMI Galaxy Survey. Specifically, we study how the spatially integrated global age and metallicity of in idual quiescent galaxies vary in the mass–size plane, using the stellar mass M* and a dynamical mass proxy derived from the virial theorem MD ∝ σ2 Re. We find that, similarly to at low redshift, the metallicity of quiescent galaxies at 0.60 ≤ $z$ ≤ 0.76 closely correlates with M/Re (a proxy for the gravitational potential or escape velocity), in that galaxies with deeper potential wells are more metal-rich. This supports the hypothesis that the relation arises due to the gravitational potential regulating the retention of metals by determining the escape velocity for metal-rich stellar and supernova ejecta to escape the system and avoid being recycled into later stellar generations. Conversely, we find no correlation between age and surface density ($M/R_\\mathrm{e}^2$) at 0.60 ≤ $z$ ≤ 0.76, despite this relation being strong at low redshift. We consider this change in the age–$M/R_\\mathrm{e}^2$ relation in the context of the redshift evolution of the star-forming and quiescent mass–size relations, and find our results are consistent with galaxies forming more compactly at higher redshifts and remaining compact throughout their evolution. Furthermore, galaxies appear to quench at a characteristic surface density that decreases with decreasing redshift. The $z$ ∼ 0 age–$M/R_\\mathrm{e}^2$ relation is therefore a result of building up the quiescent and star-forming populations with galaxies that formed at a range of redshifts and therefore a range of surface densities.
Publisher: American Astronomical Society
Date: 23-06-2023
Abstract: We present new Spitzer Infrared Array Camera (IRAC) 3.6 and 4.5 μ m mosaics of three fields, E-COSMOS, DEEP2-F3, and ELAIS-N1. Our mosaics include both new IRAC observations as well as reprocessed archival data in these fields. These fields are part of the HSC-Deep grizy survey and have a wealth of additional ancillary data. The addition of these new IRAC mosaics is critical in allowing for improved photometric redshifts and stellar population parameters at cosmic noon and earlier epochs. The total area mapped by this work is ∼17 deg 2 with a mean integration time of ≈1200s, providing a median 5 σ depth of 23.7(23.3) at 3.6(4.5) μ m in AB. We perform SExtractor photometry both on the combined mosaics as well as the single-epoch mosaics taken ≈6 months apart. The resultant IRAC number counts show good agreement with previous studies. In combination with the wealth of existing and upcoming spectrophotometric data in these fields, our IRAC mosaics will enable a wide range of galactic evolution and AGN studies. With that goal in mind, we make the combined IRAC mosaics and coverage maps of these three fields publicly available.
Publisher: American Astronomical Society
Date: 22-04-2016
Location: United States of America
Start Date: 2023
End Date: 12-2025
Amount: $375,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2014
End Date: 12-2017
Amount: $360,000.00
Funder: Australian Research Council
View Funded Activity