ORCID Profile
0000-0001-7160-3632
Current Organisations
Yale University
,
University of Arkansas at Pine Bluff
,
University of Massachusetts Amherst
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
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.
Sensory Processes, Perception and Performance | Psychology | 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: 11-08-2016
Publisher: Elsevier BV
Date: 10-2020
Publisher: Elsevier BV
Date: 04-2020
Publisher: American Astronomical Society
Date: 23-05-2023
Abstract: We select and characterize a s le of massive (log( M * / M ⊙ ) 10.6) quiescent galaxies (QGs) at 3 z 5 in the latest Cosmological Evolution Survey catalog (COSMOS2020). QGs are selected using a new rest-frame color-selection method, based on their probability of belonging to the quiescent group defined by a Gaussian mixture model (GMM) trained on rest-frame colors ( NUV − U , U − V , V − J ) of similarly massive galaxies at 2 z 3. We calculate the quiescent probability threshold above which a galaxy is classified as quiescent using simulated galaxies from the shark semi-analytical model. We find that, at z ≥ 3 in shark , the GMM/ NUVU − VJ method outperforms classical rest-frame UVJ selection and is a viable alternative. We select galaxies as quiescent based on their probability in COSMOS2020 at 3 z 5, and compare the selected s le to both UVJ - and NUVrJ -selected s les. We find that, although the new selection matches UVJ and NUVrJ in number, the overlap between color selections is only ∼50%–80%, implying that rest-frame color commonly used at lower-redshift selections cannot be equivalently used at z 3. We compute median rest-frame spectral energy distributions for our s le and find the median QG at 3 z 5 has a strong Balmer/4000 Å break, and residual NUV flux indicating recent quenching. We find the number densities of the entire quiescent population (including post-starbursts) more than doubles from 3.5 ± 2.2 × 10 −6 Mpc −3 at 4 z 5 to 1.4 ± 0.4 × 10 −5 Mpc −3 at 3 z 4, confirming that the onset of massive galaxy quenching occurs as early as 3 z 5.
Publisher: American Astronomical Society
Date: 27-12-2019
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: 23-07-2015
Publisher: Informa UK Limited
Date: 14-02-2018
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: 02-09-2015
Publisher: American Astronomical Society
Date: 25-08-2016
Publisher: American Astronomical Society
Date: 07-2021
Publisher: American Astronomical Society
Date: 06-07-2017
Publisher: American Astronomical Society
Date: 03-04-2017
Publisher: Elsevier BV
Date: 12-2020
Publisher: American Astronomical Society
Date: 24-01-2017
Publisher: American Astronomical Society
Date: 03-11-2014
Publisher: Elsevier BV
Date: 07-2020
Publisher: Springer Science and Business Media LLC
Date: 22-02-2023
Publisher: American Astronomical Society
Date: 09-2022
Abstract: We use the panchromatic spectral energy distribution (SED)-fitting code Prospector to measure the galaxy log M *–logSFR relationship (the star-forming sequence ) across 0.2 z 3.0 using the COSMOS-2015 and 3D-HST UV-IR photometric catalogs. We demonstrate that the chosen method of identifying star-forming galaxies introduces a systematic uncertainty in the inferred normalization and width of the star-forming sequence, peaking for massive galaxies at ∼0.5 and ∼0.2 dex, respectively. To avoid this systematic, we instead parameterize the density of the full galaxy population in the log M *–logSFR–redshift plane using a flexible neural network known as a normalizing flow. The resulting star-forming sequence has a low-mass slope near unity and a much flatter slope at higher masses, with a normalization 0.2–0.5 dex lower than typical inferences in the literature. We show this difference is due to the sophistication of the Prospector stellar populations modeling: the nonparametric star formation histories naturally produce higher masses while the combination of in idualized metallicity, dust, and star formation history constraints produce lower star formation rates (SFRs) than typical UV+IR formulae. We introduce a simple formalism to understand the difference between SFRs inferred from SED fitting and standard template-based approaches such as UV+IR SFRs. Finally, we demonstrate the inferred star-forming sequence is consistent with predictions from theoretical models of galaxy formation, resolving a long-standing ∼ 0.2–0.5 dex offset with observations at 0.5 z 3. The fully trained normalizing flow including a nonparametric description of ρ ( log M * , logSFR , z ) is available online 20 20 rleja/sfs_leja_trained_flow to facilitate straightforward comparisons with future work.
Publisher: American Astronomical Society
Date: 02-2021
Abstract: For the extremely bright lensed galaxy SDSS J1723+3411 at z = 1.3293, we analyze spatially integrated MMT, Keck, and Hubble Space Telescope spectra that fully cover the rest-frame wavelength range of 1400–7200 Å. We also analyze near-IR spectra from Gemini that cover H α for a portion of the lensed arc. We report fluxes for 42 detected emission lines, and upper limits for an additional 22. This galaxy has extreme emission-line ratios and high equivalent widths that are characteristic of extreme emission-line galaxies. We compute strong emission-line diagnostics from both the rest-frame optical and rest-frame ultraviolet (UV), to constrain physical conditions and test the spectral diagnostics themselves. We tightly determine the nebular physical conditions using the most reliable diagnostics, and then compare to results from other diagnostics. We find disappointing performance from the UV-only diagnostics: they either are unable to measure the metallicity or dramatically underestimate it they overestimate the pressure and the UV diagnostic of ionization parameter has a strong metallicity dependence in this regime. Based on these results, we suggest that upcoming James Webb Space Telescope (JWST) spectroscopic surveys of galaxies in the reionization epoch should invest the additional integration time to capture the optical [O ii ] and [O iii ] emission lines, and not rely solely on the rest-frame UV emission lines. We make available the spectra they represent one of the highest-quality emission-line spectral atlases of star-forming galaxies available beyond the local universe, and will aid the planning of observations with JWST.
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: 09-2023
Publisher: American Astronomical Society
Date: 18-06-2018
Publisher: Elsevier BV
Date: 2020
DOI: 10.1016/J.AQUATOX.2019.105348
Abstract: Various strategies exist to control noxious cyanobacterial populations, although the application of a newly developed granular compound (sodium carbonate peroxyhydrate 'SCP', trade name 'PAK® 27' algaecide) containing hydrogen peroxide (H
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: Springer Science and Business Media LLC
Date: 11-03-2021
Publisher: American Astronomical Society
Date: 20-03-2017
Publisher: American Astronomical Society
Date: 23-03-2201
Publisher: American Astronomical Society
Date: 10-10-2016
Publisher: American Astronomical Society
Date: 22-09-2015
Publisher: American Astronomical Society
Date: 26-10-2023
Publisher: American Astronomical Society
Date: 14-03-2017
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: 31-01-2018
Publisher: American Astronomical Society
Date: 07-2023
Abstract: We report ALMA detections of [C ii ] and a dust continuum in Az9, a multiply imaged galaxy behind the Frontier Field cluster MACS J0717.5+3745. The bright [C ii ] emission line provides a spectroscopic redshift of z = 4.274. This strongly lensed ( μ = 7 ± 1) galaxy has an intrinsic stellar mass of only 2 × 10 9 M ⊙ and a total star formation rate of 26 M ⊙ yr −1 (∼80% of which is dust-obscured). Using public magnification maps, we reconstruct the [C ii ] emission in the source plane to reveal a stable, rotation-dominated disk with V / σ = 5.3, which is × higher than predicted from simulations for similarly high-redshift, low-mass galaxies. In the source plane, the [C ii ] disk has a half-light radius of 1.8 kpc and, along with the dust, is spatially offset from the peak of the stellar light by 1.4 kpc. Az9 is not deficient in [C ii ] L [C II ] / L IR = 0.0027, consistent with local and high-redshift normal star-forming galaxies. While dust-obscured star formation is expected to dominate in higher-mass galaxies, such a large reservoir of dust and gas in a lower-mass disk galaxy 1.4 Gyr after the Big Bang challenges our picture of early galaxy evolution. Furthermore, the prevalence of such low-mass dusty galaxies has important implications for the selection of the highest-redshift dropout galaxies with JWST. As one of the lowest stellar mass galaxies at z 4 to be detected in a dust continuum and [C ii ], Az9 is an excellent laboratory in which to study early dust enrichment in the interstellar medium.
Location: United States of America
Location: United States of America
Start Date: 2014
End Date: 12-2017
Amount: $360,000.00
Funder: Australian Research Council
View Funded Activity