Absorption-line abundances in the smc-like galaxy ugc 5282: Evidence of ism dilution from inflows on kiloparsec Scales

David V. Bowen, Todd M. Tripp, Edward B. Jenkins, Max Pettini, Doron Chelouche, Renyue Cen, Donald G. York

Research output: Contribution to journalArticlepeer-review

Abstract

We present a Hubble Space Telescope Cosmic Origins Spectrograph spectrum of the QSO SDSS J095109.12 +330745.8 (zem= 0.645) whose sightline passes through the SMC-like dwarf galaxy UGC 5282 (MB= -16.0, cz = 1577 km s-1), 1.2 kpc in projection from the central H II region of the galaxy. Damped Lyα (DLA) absorption is detected at the redshift of UGC 5282 with log [N(H I) cm-2]=20.89+0.12 -0.21. Analysis of the accompanying S II, PII, and O I metal lines yields a neutral gas metallicity, ZH I, of [S/H] ≃ [P/H] =-0.80 ± 0.24. The metallicity of ionized gas from the central H II region ZH II measured from its emission lines is [O/H] =-0.37 ± 0.10, a difference of +0.43 ± 0.26 from ZH I. This difference δ is consistent with that seen toward H II regions in other star-forming galaxies and supports the idea that ionized gas near starforming regions shows systematically higher metallicities than exist in the rest of a galaxy s neutral interstellar medium (ISM). The positive values of δ found in UGC 5282 (and the other star-forming galaxies) is likely due to infalling low-metallicity gas from the intergalactic medium that mixes with the galaxy s ISM on kiloparsec scales. This model is also consistent with broad Lyα emission detected at the bottom of the DLA absorption, offset by ∼125 km s-1 from the absorption velocity. Models of galaxy evolution that attempt to replicate population characteristics, such as the mass metallicity relation, may need to start with a galaxy metallicity represented by ZH I rather than that measured traditionally from ZH II

Original languageEnglish
Article number84
JournalAstrophysical Journal
Volume893
Issue number1
DOIs
StatePublished - 10 Apr 2020

Bibliographical note

Funding Information:
the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555

Publisher Copyright:
© 2020. The American Astronomical Society. All rights reserved

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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