We use medium- and high-resolution spectroscopy of close pairs of quasars to analyze the circumgalactic medium (CGM) surrounding 32 damped Ly
The bimodal absorption system imaging campaign (BASIC) aims to characterize the galaxy environments of a sample of 36 H
- Award ID(s):
- 2044303
- NSF-PAR ID:
- 10397511
- Publisher / Repository:
- DOI PREFIX: 10.3847
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 944
- Issue:
- 1
- ISSN:
- 0004-637X
- Format(s):
- Medium: X Size: Article No. 101
- Size(s):
- ["Article No. 101"]
- Sponsoring Org:
- National Science Foundation
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Abstract α absorption systems (DLAs). The primary quasar sightline in each pair probes an intervening DLA in the redshift range 1.6 <z abs< 3.5, such that the secondary sightline probes absorption from Lyα and a large suite of metal-line transitions (including Oi , Cii , Civ , Siii , and Siiv ) in the DLA host galaxy’s CGM at transverse distances 24 kpc ≤R ⊥≤ 284 kpc. Analysis of Lyα in the CGM sightlines shows an anticorrelation betweenR ⊥and Hi column density (N HI) with 99.8% confidence, similar to that observed around luminous galaxies. The incidences of Cii and Siii withN > 1013cm−2within 100 kpc of DLAs are larger by 2σ than those measured in the CGM of Lyman break galaxies (Cf (N CII ) > 0.89 and ). Metallicity constraints derived from ionic ratios for nine CGM systems with negligible ionization corrections andN HI> 1018.5cm−2show a significant degree of scatter (with metallicities/limits across the range ), suggesting inhomogeneity in the metal distribution in these environments. Velocity widths of Civ λ 1548 and low-ionization metal species in the DLA versus CGM sightlines are strongly (>2σ ) correlated, suggesting that they trace the potential well of the host halo overR ⊥≲ 300 kpc scales. At the same time, velocity centroids for Civ λ 1548 differ in DLA versus CGM sightlines by >100 km s−1for ∼50% of velocity components, but few components have velocities that would exceed the escape velocity assuming dark matter host halos of ≥1012M ⊙. -
Abstract We present a Keck/MOSFIRE rest-optical composite spectrum of 16 typical gravitationally lensed star-forming dwarf galaxies at 1.7 ≲
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, at fixedM *and SFR, of the locally defined fundamental metallicity relation. We measure the doublet ratio [Oii ]λ 3729/[Oii ]λ 3726 = 1.56 ± 0.32 (1.51 ± 0.12) and a corresponding electron density of ( ) when considering the bootstrapped (statistical-only) error spectrum. This result suggests that lower-mass galaxies have lower densities than higher-mass galaxies atz ∼ 2. -
Abstract We present the KODIAQ-Z survey aimed to characterize the cool, photoionized gas at 2.2 ≲
z ≲ 3.6 in 202 Hi -selected absorbers with 14.6 ≤ < 20 that probe the interface between galaxies and the intergalactic medium (IGM). We find that gas with at 2.2 ≲z ≲ 3.6 can be metal-rich (−1.6 ≲ [X/H] ≲ − 0.2) as seen in damped Lyα absorbers (DLAs); it can also be very metal-poor ([X/H] < − 2.4) or even pristine ([X/H] < − 3.8), which is not observed in DLAs but is common in the IGM. For absorbers, the frequency of pristine absorbers is about 1%–10%, while for absorbers it is 10%–20%, similar to the diffuse IGM. Supersolar gas is extremely rare (<1%) at these redshifts. The factor of several thousand spread from the lowest to highest metallicities and large metallicity variations (a factor of a few to >100) between absorbers separated by less than Δv < 500 km s−1imply that the metals are poorly mixed in gas. We show that these photoionized absorbers contribute to about 14% of the cosmic baryons and 45% of the cosmic metals at 2.2 ≲z ≲ 3.6. We find that the mean metallicity increases withN Hi , consistent with what is found inz < 1 gas. The metallicity of gas in this column density regime has increased by a factor ∼8 from 2.2 ≲z ≲ 3.6 toz < 1, but the contribution of the absorbers to the total metal budget of the universe atz < 1 is a quarter of that at 2.2 ≲z ≲ 3.6. We show that FOGGIE cosmological zoom-in simulations have a similar evolution of [X/H] withN Hi , which is not observed in lower-resolution simulations. In these simulations, very metal-poor absorbers with [X/H] < − 2.4 atz ∼ 2–3 are tracers of inflows, while higher-metallicity absorbers are a mixture of inflows and outflows. -
Abstract Abundances of chemical elements in the interstellar and circumgalactic media of high-redshift galaxies offer important constraints on the nucleosynthesis by early generations of stars. Damped Ly
α absorbers (DLAs) in spectra of high-redshift background quasars are excellent sites for obtaining robust measurements of element abundances in distant galaxies. Past studies of DLAs at redshiftsz > 4 have measured abundances of ≲0.01 solar. Here we report the discovery of a DLA atz = 4.7372 with an exceptionally high degree of chemical enrichment. We estimate the Hi column density in this absorber to be log (N H I/cm−2) = 20.48 ± 0.15. Our analysis shows unusually high abundances of carbon and oxygen ([C/H] = 0.88 ± 0.17, [O/H] = 0.71 ± 0.16). Such a high level of enrichment a mere 1.2 Gyr after the Big Bang is surprising because of insufficient time for the required amount of star formation. To our knowledge, this is the first supersolar absorber found atz > 4.5. We find the abundances of Si and Mg to be [Si/H] = and [Mg/H] = , confirming the metal-rich nature of this absorber. By contrast, Fe shows a much lower abundance ([Fe/H] = ). We discuss implications of our results for galactic chemical evolution models. The metallicity of this absorber is higher than that of any other known DLA and is >2 orders of magnitude above predictions of chemical evolution models and theN H I-weighted mean metallicity from previous studies atz > 4.5. The relative abundances (e.g., [O/Fe] = 2.29 ± 0.05, [C/Fe] = 2.46 ± 0.08) are also highly unusual compared to predictions for enrichment by early stars. -
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