MNRAS 000, 1–20 (0000) Preprint 12 May 2021 Compiled using MNRAS L
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A partial Lyman limit system tracing intragroup gas at ≈ 0. 8
towards HE 1003 + 0149
Anand Narayanan
1 ★
, Sameer
2
, Sowgat Muzahid
3,4
, Sean D. Johnson
5
, Purvi Udhwani
1
,
Jane C. Charlton
2
, Valentin Mauerhofer
6,7
, Joop Schaye
8
, Mathin Yadav
1
,
1
Department of Earth and Space Sciences, Indian Institute of Space Science & Technology, Thiruvananthapuram 695547, Kerala, INDIA
2
Department of Astronomy & Astrophysics, The Pennsylvania State University, 525 Davey Laboratory University Park, PA, 16802, USA
3
Inter-University Centre for Astronomy & Astrophysics, Post Bag 4, Ganeshkhind, Savitribai Phule Pune University Campus, Pune 411 007, India
4
Leibniz-Institut fuÜr Astrophysik Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam, Germany
5
Department of Astronomy, 1085 S. University, 323 West Hall, Ann Arbor, MI 48109-1107, USA
6
Observatoire de Genéve, Université de Genéve, Chemin Pegasi 51, 1290 Versoix, Switzerland
7
Univ Lyon, Univ Lyon1, ENS de Lyon, CNRS, Centre de Recherche Astrophysique de Lyon UMR5574, 69230 Saint-Genis-Laval, France
8
Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, the Netherlands.
12 May 2021
ABSTRACT
We present analysis of the galaxy environment and physical properties of a partial Lyman
limit system at = 0.83718 with H i and metal line components closely separated in redshift
space ( | Δ |≈ 400 km s
−1
) towards the background quasar HE 1003 + 0149. The /COS far-
ultraviolet spectrum providescoverage of lines of oxygen ions from O i to O v. Comparison
of observed spectral lines with synthetic profiles generated from Bayesian ionization modeling
reveals the presence of two distinct gas phases in the absorbing medium. The low-ionization
phase of the absorber has sub-solar metallicities (∼ 1/10 solar) with indications of [C/O] < 0
in each of three components. The O iv and O v trace a more diffuse higher-ionization medium
with predicted H i column densities that are ≈ 2 dex lower. The quasar field observed with
/MUSE reveals three dwarf galaxies with stellar masses of
∗
∼ 10
8
− 10
9
M
⊙
, and
with star formation rates of ≈ 0.5 − 1M⊙ yr
−1
, at projected separations of /
vir
≈ 1.8 − 3.0
from the absorber. Over a wider field with projected proper separation of ≤ 5 Mpc and radial
velocity offset of | Δ |≤ 1000 km s
−1
from the absorber, 21 more galaxies are identified in
the /VIMOS and Magellan deep galaxy redshift surveys, with 8 of them within 1 Mpc
and 500 km s
−1
, consistent with the line of sight penetrating a group of galaxies. The absorber
presumably traces multiple phases of cool ( ∼ 10
4
K) photoionized intragroup medium. The
inferred [C/O] < 0 hint at preferential enrichment from core-collapse supernovae, with such
gas displaced from one or more of the nearby galaxies, and confined to the group medium.
Key words: (galaxies:) quasars: absorption lines, galaxies: haloes, galaxies: groups: general,
(galaxies:) intergalactic medium
1 INTRODUCTION
The gaseous halos of galaxies and the regions where they connect
with the filaments of the intergalactic medium hold substantial bary-
onic mass in the form of metals and H i, comparable to the gaseous
disks of galaxies. These regions bear the imprint of large-scale gas
flows in and out of galaxies which in turn regulates galaxy evolution.
Among the different classes of quasar absorbers, the partial Lyman
limit and Lyman limit systems (pLLS and LLS) trace halo gas bound
to galaxies and in the extended unbound medium referred to as the
circumgalactic medium (CGM; Shull et al. 2014). These absorption
★
E-mail: anand@iist.ac.in
systems, are defined to be partially or fully optically thick at the
Lyman limit, which corresponds to neutral gas column densities of
16 ≤ log [ ( H i)/cm
−2
]≤ 17.2, and log [ ( H i)/cm
−2
]≥ 17.2
respectively. Recently, several authors have also highlighted the
importance of pLLS and LLS as a means to discern inflows and
outflows from galaxies. Lehner et al. (2013) found a bimodal-
ity in the metallicity distribution for a sample of low redshift
( ≤ 1) absorbers having 16.2 ≤ log [ ( H i)/cm
−2
] ≤ 18.5
with distinct peaks at log( /
⊙
) = −0.3, and −1.6, and a dip
at log( /
⊙
)≈−1. The metal enriched portion of this sample is
seen as tracing gas outflows from galaxies while the low metallicity
portion is interpreted as accretion of cool gas from the IGM onto
galaxies (Wotta et al. 2016). A higher fraction of this metal-poor
© 0000 The Authors
arXiv:2105.04841v1 [astro-ph.GA] 11 May 2021