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Characterizing the Circumgalactic Medium of the Lowest-mass Galaxies: A Case Study of IC 1613

Zheng, Yong and Emerick, Andrew and Putman, Mary E. and Werk, Jessica K. and Kirby, Evan N. and Peek, Joshua (2020) Characterizing the Circumgalactic Medium of the Lowest-mass Galaxies: A Case Study of IC 1613. Astrophysical Journal, 905 (2). Art. No. 133. ISSN 1538-4357. doi:10.3847/1538-4357/abc875.

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Using 10 sight lines observed with the Hubble Space Telescope/Cosmic Origins Spectrograph, we study the circumgalactic medium (CGM) and outflows of IC 1613, which is a low-mass (M_* ~ 10⁸ M_⊙), dwarf irregular galaxy on the outskirts of the Local Group. Among the sight lines, four are pointed toward UV-bright stars in IC 1613, and the other six sight lines are background QSOs at impact parameters from 6 kpc (<0.1R_(200)) to 61 kpc (0.6R_(200)). We detect a number of Si ii, Si iii, Si iv, C ii, and C iv absorbers, most of which have velocities less than the escape velocity of IC 1613 and thus are gravitationally bound. The line strengths of these ion absorbers are consistent with the CGM absorbers detected in dwarf galaxies at low redshifts. Assuming that Si ii, Si iii, and Si iv comprise nearly 100% of the total silicon, we find 3% (~8 × 10³ M_⊙), 2% (~7 × 10³ M_⊙), and 32%–42% [~(1.0–1.3) × 10⁵ M_⊙] of the silicon mass in the stars, interstellar medium, and within 0.6R_(200) of the CGM of IC 1613. We also estimate the metal outflow rate to be Ṁ_(out,Z) ⩾ 1.1 x 10⁻⁵ M_⊙ yr⁻¹ and the instantaneous metal mass loading factor to be η_Z ≥ 0.004, which are in broad agreement with available observation and simulation values. This work is the first time a dwarf galaxy of such low mass is probed by a number of both QSO and stellar sight lines, and it shows that the CGM of low-mass, gas-rich galaxies can be a large reservoir enriched with metals from past and ongoing outflows.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Zheng, Yong0000-0003-4158-5116
Emerick, Andrew0000-0003-2807-328X
Putman, Mary E.0000-0002-1129-1873
Werk, Jessica K.0000-0002-0355-0134
Kirby, Evan N.0000-0001-6196-5162
Peek, Joshua0000-0003-4797-7030
Additional Information:© 2020. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2020 August 11; revised 2020 October 26; accepted 2020 November 6; published 2020 December 22. We thank R. Bordoloi for sharing his python code of escape velocity calculation, E. Patel for discussing the projection effect between the Magellanic System and the LG galaxies using hydrodynamic simulations and HST/Gaia proper motion measurements, and D. Weisz for discussing many aspects of this paper and for his great support as a faculty mentor to Y.Z. at Miller Institute at UC Berkeley. We also thank A. Fox and P. Richter for helpful discussion on the manuscript. Y.Z. acknowledges support from the Miller Institute for Basic Research in Science. Support for Program number HST-GO-15156 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555. This material is based upon work supported by the National Science Foundation under grant No. AST-1847909. E.N.K. gratefully acknowledges support from a Cottrell Scholar award administered by the Research Corporation for Science Advancement. This research has made use of the HSLA database, developed and maintained at STScI, Baltimore, USA. Facilities: Hubble Space Telescope/Cosmic Origins Spectrograph - , Mikulski Archive for Space Telescopes (MAST). - Software: Astropy (The Astropy Collaboration et al. 2018), Numpy (Harris et al. 2020), Matplotlib (Hunter 2007), CLOUDY (Ferland et al. 2017), IDL, the gala package (Price-Whelan et al. 2017).
Group:TAPIR, Astronomy Department
Funding AgencyGrant Number
Miller Institute for Basic Research in ScienceUNSPECIFIED
Cottrell Scholar of Research CorporationUNSPECIFIED
Subject Keywords:Circumgalactic medium ; Local Group; Magellanic Stream ; Metallicity ; Dwarf irregular galaxies
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: Circumgalactic medium (1879); Local Group (929); Magellanic Stream (991); Metallicity (1031); Dwarf irregular galaxies (417)
Record Number:CaltechAUTHORS:20201224-085807319
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:107276
Deposited By: George Porter
Deposited On:04 Jan 2021 15:34
Last Modified:16 Nov 2021 19:01

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