ORCID Profile
0000-0001-6065-7483
Current Organisations
University of Arizona Department of Astronomy and Steward Observatory
,
MMT Observatory
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.
Publisher: American Astronomical Society
Date: 03-2023
Abstract: We present rest-frame optical emission-line flux ratio measurements for five z 5 galaxies observed by the James Webb Space Telescope Near-Infared Spectrograph (NIRSpec) in the SMACS 0723 Early Release Observations. We add several quality-control and post-processing steps to the NIRSpec pipeline reduction products in order to ensure reliable relative flux calibration of emission lines that are closely separated in wavelength, despite the uncertain absolute spectrophotometry of the current version of the reductions. Compared to z ∼ 3 galaxies in the literature, the z 5 galaxies have similar [O iii ] λ 5008/H β ratios, similar [O iii ] λ 4364/H γ ratios, and higher (∼0.5 dex) [Ne III ] λ 3870/[O II ] λ 3728 ratios. We compare the observations to MAPPINGS V photoionization models and find that the measured [Ne III ] λ 3870/[O II ] λ 3728, [O iii ] λ 4364/H γ , and [O iii ] λ 5008/H β emission-line ratios are consistent with an interstellar medium (ISM) that has very high ionization ( log ( Q ) ≃ 8 − 9 , units of cm s −1 ), low metallicity ( Z / Z ⊙ ≲ 0.2), and very high pressure ( log ( P / k ) ≃ 8 − 9 , units of cm −3 ). The combination of [O iii ] λ 4364/H γ and [O iii ] λ (4960 + 5008)/H β line ratios indicate very high electron temperatures of 4.1 log ( T e / K ) 4.4 , further implying metallicities of Z / Z ⊙ ≲ 0.2 with the application of low-redshift calibrations for “ T e -based” metallicities. These observations represent a tantalizing new view of the physical conditions of the ISM in galaxies at cosmic dawn.
Publisher: American Astronomical Society
Date: 09-04-2015
Publisher: American Astronomical Society
Date: 10-08-2007
DOI: 10.1086/519294
Publisher: American Astronomical Society
Date: 18-04-2012
Publisher: American Astronomical Society
Date: 18-06-2018
Publisher: Oxford University Press (OUP)
Date: 31-10-2020
Abstract: Massive galaxy clusters undergo strong evolution from z ∼ 1.6 to z ∼ 0.5, with overdense environments at high-z characterized by abundant dust-obscured star formation and stellar mass growth which rapidly give way to widespread quenching. Data spanning the near- to far-infrared (IR) can directly trace this transformation however, such studies have largely been limited to the massive galaxy end of cluster populations. In this work, we present ‘total light’ stacking techniques spanning $3.4\\!-\\!500\\, \\mu$m aimed at revealing the total cluster emission, including low-mass members and potential intracluster dust. We detail our procedures for WISE, Spitzer, and Herschel imaging, including corrections to recover the total stacked emission in the case of high fractions of detected galaxies. We apply our techniques to 232 well-studied log$\\, M_{200}/\\mathrm{M}_{\\odot }\\sim 13.8$ clusters in multiple redshift bins, recovering extended cluster emission at all wavelengths. We measure the averaged IR radial profiles and spectral energy distributions (SEDs), quantifying the total stellar and dust content. The near-IR profiles are well described by an NFW model with a high (c ∼ 7) concentration. Dust emission is similarly concentrated, albeit suppressed at $r\\lesssim 0.3\\,$Mpc. The measured SEDs lack warm dust, consistent with the colder SEDs of low-mass galaxies. We derive total stellar masses consistent with the theoretical Mhalo−M⋆ relation and specific star formation rates that evolve strongly with redshift, echoing that of log$\\, M_{\\star }/\\mathrm{M}_{\\odot }\\gtrsim 10$ cluster galaxies. Separating out the massive population reveals the majority of cluster far-IR emission ($\\sim 70\\!-\\!80{{\\ \\rm per\\ cent}}$) is provided by the low-mass constituents, which differs from field galaxies. This effect may be a combination of mass-dependent quenching and excess dust in low-mass cluster galaxies.
Publisher: American Astronomical Society
Date: 25-06-2010
Publisher: American Astronomical Society
Date: 30-01-2014
Publisher: American Astronomical Society
Date: 30-01-2014
Publisher: American Astronomical Society
Date: 09-2022
Abstract: We use deep spectroscopy from the Hubble Space Telescope Wide-Field-Camera 3 IR grisms combined with broadband photometry to study the stellar populations, gas ionization and chemical abundances in star-forming galaxies at z ∼ 1.1–2.3. The data stem from the CANDELS Ly α Emission At Reionization (CLEAR) survey. At these redshifts, the grism spectroscopy measure the [O II ] λ λ 3727, 3729, [O III ] λ λ 4959, 5008, and H β strong emission features, which constrain the ionization parameter and oxygen abundance of the nebular gas. We compare the line-flux measurements to predictions from updated photoionization models (MAPPINGS V Kewley et al.), which include an updated treatment of nebular gas pressure, log P / k = n e T e . Compared to low-redshift s les ( z ∼ 0.2) at fixed stellar mass, log M * / M ⊙ = 9.4–9.8, the CLEAR galaxies at z = 1.35 (1.90) have lower gas-phase metallicity, Δ ( log Z ) = 0.25 (0.35) dex, and higher ionization parameters, Δ ( log q ) = 0.25 (0.35) dex, where U ≡ q / c . We provide updated analytic calibrations between the [O III ], [O II ], and H β emission-line ratios, metallicity, and ionization parameter. The CLEAR galaxies show that at fixed stellar mass, the gas ionization parameter is correlated with the galaxy specific star formation rates, where Δ log q ≃ 0.4 × Δ ( log sSFR ) , derived from changes in the strength of galaxy H β equivalent width. We interpret this as a consequence of higher gas densities, lower gas covering fractions, combined with a higher escape fraction of H-ionizing photons. We discuss both tests to confirm these assertions and implications this has for future observations of galaxies at higher redshifts.
Publisher: American Astronomical Society
Date: 05-2022
Abstract: Strong galactic winds are ubiquitous at z ≳ 1. However, it is not well-known where inside galaxies these winds are launched from. We study the cool winds (∼10 4 K) in two spatial regions of a massive galaxy at z = 1.3, which we nickname the “Baltimore Oriole’s Nest.” The galaxy has a stellar mass of 10 10.3±0.3 M ⊙ , is located on the star-forming main sequence, and has a morphology indicative of a recent merger. Gas kinematics indicate a dynamically complex system with velocity gradients ranging from 0 to 60 km s −1 . The two regions studied are: a dust-reddened center (Central region), and a blue arc at 7 kpc from the center (Arc region). We measure the Fe ii and Mg ii absorption line profiles from deep Keck/DEIMOS spectra. Blueshifted wings up to 450 km s −1 are found for both regions. The Fe ii column densities of winds are 10 14.7±0.2 cm −2 and 10 14.6±0.2 cm −2 toward the Central and Arc regions, respectively. Our measurements suggest that the winds are most likely launched from both regions. The winds may be driven by the spatially extended star formation, the surface density of which is around 0.2 M ⊙ yr −1 · kpc −2 in both regions. The mass outflow rates are estimated to be 4 M ⊙ yr −1 and 3 M ⊙ yr −1 for the Central and Arc regions, with uncertainties of one order of magnitude or more. The findings of this work and a few previous studies suggest that the cool galactic winds at z ≳ 1 might be commonly launched from the entire spatial extents of their host galaxies, due to extended galaxy star formation.
Publisher: American Astronomical Society
Date: 09-12-2009
Publisher: American Astronomical Society
Date: 22-02-2023
Abstract: A key component of the Dark Energy Spectroscopic Instrument (DESI) survey validation (SV) is a detailed visual inspection (VI) of the optical spectroscopic data to quantify key survey metrics. In this paper we present results from VI of the quasar survey using deep coadded SV spectra. We show that the majority (≈70%) of the main-survey targets are spectroscopically confirmed as quasars, with ≈16% galaxies, ≈6% stars, and ≈8% low-quality spectra lacking reliable features. A nonnegligible fraction of the quasars are misidentified by the standard spectroscopic pipeline, but we show that the majority can be recovered using post-pipeline “afterburner” quasar-identification approaches. We combine these “afterburners” with our standard pipeline to create a modified pipeline to increase the overall quasar yield. At the depth of the main DESI survey, both pipelines achieve a good-redshift purity (reliable redshifts measured within 3000 km s −1 ) of ≈99% however, the modified pipeline recovers ≈94% of the visually inspected quasars, as compared to ≈86% from the standard pipeline. We demonstrate that both pipelines achieve a median redshift precision and accuracy of ≈100 km s −1 and ≈70 km s −1 , respectively. We constructed composite spectra to investigate why some quasars are missed by the standard pipeline and find that they are more host-galaxy dominated (i.e., distant analogs of “Seyfert galaxies”) and/or more dust reddened than the standard-pipeline quasars. We also show ex le spectra to demonstrate the overall ersity of the DESI quasar s le and provide strong-lensing candidates where two targets contribute to a single spectrum.
Publisher: American Astronomical Society
Date: 08-12-2014
Publisher: American Astronomical Society
Date: 07-11-2013
Publisher: American Astronomical Society
Date: 2023
Abstract: The Dark Energy Spectroscopic Instrument (DESI) Survey has obtained a set of spectroscopic measurements of galaxies to validate the final survey design and target selections. To assist in these tasks, we visually inspect DESI spectra of approximately 2500 bright galaxies, 3500 luminous red galaxies (LRGs), and 10,000 emission-line galaxies (ELGs) to obtain robust redshift identifications. We then utilize the visually inspected redshift information to characterize the performance of the DESI operation. Based on the visual inspection (VI) catalogs, our results show that the final survey design yields s les of bright galaxies, LRGs, and ELGs with purity greater than 99%. Moreover, we demonstrate that the precision of the redshift measurements is approximately 10 km s −1 for bright galaxies and ELGs and approximately 40 km s −1 for LRGs. The average redshift accuracy is within 10 km s −1 for the three types of galaxies. The VI process also helps improve the quality of the DESI data by identifying spurious spectral features introduced by the pipeline. Finally, we show ex les of unexpected real astronomical objects, such as Ly α emitters and strong lensing candidates, identified by VI. These results demonstrate the importance and utility of visually inspecting data from incoming and upcoming surveys, especially during their early operation phases.
Publisher: American Astronomical Society
Date: 03-2023
Abstract: We present an investigation into the first 500 Myr of galaxy evolution from the Cosmic Evolution Early Release Science (CEERS) survey. CEERS, one of 13 JWST ERS programs, targets galaxy formation from z ∼ 0.5 to using several imaging and spectroscopic modes. We make use of the first epoch of CEERS NIRCam imaging, spanning 35.5 arcmin 2 , to search for candidate galaxies at z 9. Following a detailed data reduction process implementing several custom steps to produce high-quality reduced images, we perform multiband photometry across seven NIRCam broad- and medium-band (and six Hubble broadband) filters focusing on robust colors and accurate total fluxes. We measure photometric redshifts and devise a robust set of selection criteria to identify a s le of 26 galaxy candidates at z ∼ 9–16. These objects are compact with a median half-light radius of ∼0.5 kpc. We present an early estimate of the z ∼ 11 rest-frame ultraviolet (UV) luminosity function, finding that the number density of galaxies at M UV ∼ −20 appears to evolve very little from z ∼ 9 to 11. We also find that the abundance (surface density [arcmin −2 ]) of our candidates exceeds nearly all theoretical predictions. We explore potential implications, including that at z 10, star formation may be dominated by top-heavy initial mass functions, which would result in an increased ratio of UV light per unit halo mass, though a complete lack of dust attenuation and/or changing star formation physics may also play a role. While spectroscopic confirmation of these sources is urgently required, our results suggest that the deeper views to come with JWST should yield prolific s les of ultrahigh-redshift galaxies with which to further explore these conclusions.
Location: United States of America
Location: United States of America
No related grants have been discovered for Benjamin Weiner.