We present a Keck/MOSFIRE rest-optical composite spectrum of 16 typical gravitationally lensed star-forming dwarf galaxies at 1.7 ≲
In this work, we publish stellar velocity dispersions, sizes, and dynamical masses for eight ultramassive galaxies (UMGs;
- Publication Date:
- NSF-PAR ID:
- 10375823
- Journal Name:
- The Astrophysical Journal
- Volume:
- 938
- Issue:
- 2
- Page Range or eLocation-ID:
- Article No. 109
- ISSN:
- 0004-637X
- Publisher:
- DOI PREFIX: 10.3847
- Sponsoring Org:
- National Science Foundation
More Like this
-
Abstract z ≲ 2.6 (z mean= 2.30), all chosen independent of emission-line strength. These galaxies have a median stellar mass of and a median star formation rate of . We measure the faint electron-temperature-sensitive [Oiii ]λ 4363 emission line at 2.5σ (4.1σ ) significance when considering a bootstrapped (statistical-only) uncertainty spectrum. This yields a direct-method oxygen abundance of ( ). We investigate the applicability at highz of locally calibrated oxygen-based strong-line metallicity relations, finding that the local reference calibrations of Bian et al. best reproduce (≲0.12 dex) our composite metallicity at fixed strong-line ratio. At fixedM *, our composite is well represented by thez ∼ 2.3 direct-method stellar mass—gas-phase metallicity relation (MZR) of Sanders et al. When comparing to predicted MZRs from the IllustrisTNG and FIRE simulations, having recalculated our stellar masses with more realistic nonparametric star formation histories , we find excellent agreement with the FIRE MZR. Our composite is consistent with no metallicity evolution, atmore » -
Abstract We utilize ∼17,000 bright luminous red galaxies (LRGs) from the novel Dark Energy Spectroscopic Instrument Survey Validation spectroscopic sample, leveraging its deep (∼2.5 hr galaxy−1exposure time) spectra to characterize the contribution of recently quenched galaxies to the massive galaxy population at 0.4 <
z < 1.3. We useProspector to infer nonparametric star formation histories and identify a significant population of recently quenched galaxies that have joined the quiescent population within the past ∼1 Gyr. The highest-redshift subset (277 atz > 1) of our sample of recently quenched galaxies represents the largest spectroscopic sample of post-starburst galaxies at that epoch. At 0.4 <z < 0.8, we measure the number density of quiescent LRGs, finding that recently quenched galaxies constitute a growing fraction of the massive galaxy population with increasing look-back time. Finally, we quantify the importance of this population among massive ( > 11.2) LRGs by measuring the fraction of stellar mass each galaxy formed in the gigayear before observation,f 1 Gyr. Although galaxies withf 1 Gyr> 0.1 are rare atz ∼ 0.4 (≲0.5% of the population), byz ∼ 0.8, they constitute ∼3% of massive galaxies. Relaxing this threshold, we find that galaxies withf 1 Gyr> 5% constitute ∼10% of the massive galaxy population atz ∼more » -
Abstract We use ALMA observations of CO(2–1) in 13 massive (
M *≳ 1011M ⊙) poststarburst galaxies atz ∼ 0.6 to constrain the molecular gas content in galaxies shortly after they quench their major star-forming episode. The poststarburst galaxies in this study are selected from the Sloan Digital Sky Survey spectroscopic samples (Data Release 14) based on their spectral shapes, as part of the Studying QUenching at Intermediate-z Galaxies: Gas, angu momentum, and Evolution ( ) program. Early results showed that two poststarburst galaxies host large H2reservoirs despite their low inferred star formation rates (SFRs). Here we expand this analysis to a larger statistical sample of 13 galaxies. Six of the primary targets (45%) are detected, withM ⊙. Given their high stellar masses, this mass limit corresponds to an average gas fraction of or ∼14% using lower stellar masses estimates derived from analytic, exponentially declining star formation histories. The gas fraction correlates with theD n 4000 spectral index, suggesting that the cold gas reservoirs decrease with time since burst, as found in local K+A galaxies. Star formation histories derived from flexible stellar population synthesis modeling support thismore » -
Abstract We present a stellar dynamical mass measurement of a newly detected supermassive black hole (SMBH) at the center of the fast-rotating, massive elliptical galaxy NGC 2693 as part of the MASSIVE survey. We combine high signal-to-noise ratio integral field spectroscopy (IFS) from the Gemini Multi-Object Spectrograph with wide-field data from the Mitchell Spectrograph at McDonald Observatory to extract and model stellar kinematics of NGC 2693 from the central ∼150 pc out to ∼2.5 effective radii. Observations from Hubble Space Telescope WFC3 are used to determine the stellar light distribution. We perform fully triaxial Schwarzschild orbit modeling using the latest TriOS code and a Bayesian search in 6D galaxy model parameter space to determine NGC 2693's SMBH mass (
M BH), stellar mass-to-light ratio, dark matter content, and intrinsic shape. We find and a triaxial intrinsic shape with axis ratiosp =b /a = 0.902 ± 0.009 and , triaxiality parameterT = 0.39 ± 0.04. In comparison, the best-fit orbit model in the axisymmetric limit and (cylindrical) Jeans anisotropic model of NGC 2693 prefer and , respectively. Neither model can account for the non-axisymmetric stellar velocity features present inmore » -
Abstract We present a measurement of the intrinsic space density of intermediate-redshift (
z ∼ 0.5), massive (M *∼ 1011M ⊙), compact (R e ∼ 100 pc) starburst (ΣSFR∼ 1000M ⊙yr−1kpc−1) galaxies with tidal features indicative of them having undergone recent major mergers. A subset of them host kiloparsec-scale, > 1000 km s−1outflows and have little indication of AGN activity, suggesting that extreme star formation can be a primary driver of large-scale feedback. The aim for this paper is to calculate their space density so we can place them in a better cosmological context. We do this by empirically modeling the stellar populations of massive, compact starburst galaxies. We determine the average timescale on which galaxies that have recently undergone an extreme nuclear starburst would be targeted and included in our spectroscopically selected sample. We find that massive, compact starburst galaxies targeted by our criteria would be selectable for Myr and have an intrinsic space density . This space density is broadly consistent with ourz ∼ 0.5 compact starbursts being the most extremely compact and star-forming low-redshift analogs of the compact star-forming galaxies in the early universe, as well as them being the progenitors to a fraction of intermediate-redshift, post-starburst, andmore »