Abstract
Abstract 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 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.
Highlights
Galaxies at redshift 2.5 have lost the majority of the metals produced over their star formation histories, giving rise to the so-called missing metals problem (e.g., Bouche et al 2007; Peeples et al 2014)
Using 10 sightlines observed with the Hubble Space Telescope/Cosmic Origins Spectrograph, we study the circumgalactic medium (CGM) and outflows of IC1613, which is a low-mass (M∗ ∼ 108 M ), dwarf irregular galaxy on the outskirts of the Local Group
With 4 stellar and 6 QSO sightlines observed with HST/COS, we study the CGM and outflows of IC1613, an isolated, low-mass (M∗ ∼ 108 M ) dwarf irregular galaxy on the outskirts of the Local Group (LG)
Summary
Galaxies at redshift 2.5 have lost the majority of the metals produced over their star formation histories, giving rise to the so-called missing metals problem (e.g., Bouche et al 2007; Peeples et al 2014). 96% of the iron they have synthesized through star formation (Kirby et al 2011, 2013), with the missing iron located either in their ISM or CGM, and with some fraction possibly having escaped the galaxies altogether. Bordoloi et al (2014) find a large reservoir of carbon with mass of ≥ 1.2 × 106 M in the CGM of 43 low-mass galaxies (M∗ ∼ 108.2−10.2 M ) at redshift ≤ 0.1 Most of their C iv detection occur within 0.5 virial radius, beyond which no C iv is detected at a sensitivity limit of 50–100 mA.
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