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Abstract We explore the growth of the stellar disks in 14 nearby spiral galaxies as part of the Deciphering the Interplay between the Interstellar medium, Stars, and the Circumgalactic medium (DIISC) survey. We study the radial distribution of specific star formation rates (sSFRs) and investigate the ratio of the difference in the outer and inner sSFRs (ΔsSFR= sSFRout– sSFRin) of the disk and the total sSFR, ΔsSFR/sSFR, to quantify disk growth. We find ΔsSFR/sSFR and the Higas fraction to show a mild correlation of Spearman’sρ= 0.30, indicating that star formation and disk growth are likely to proceed outward in galactic disks with high Higas fractions. The Higas fractions and ΔsSFR/sSFR of the galaxies also increase with the distance to the nearestL⋆neighbor, suggesting that galaxies are likely to sustain the cold gas in their interstellar medium and exhibit inside-out growth in isolated environments. However, the Hicontent in their circumgalactic medium (CGM), probed by the Lyαequivalent width (WLyα) excess, is observed to be suppressed in isolated environments, as is apparent from the strong anticorrelation between theWLyαexcess and the distance to the fifth nearestL⋆neighbor (Spearman’sρ= −0.62). As expected,WLyαis also found to be suppressed in cluster galaxies. We find no relation between theWLyαexcess of the detected CGM absorber and ΔsSFR/sSFR, implying that the enhancement and suppression of the circumgalactic Higas does not affect the direction in which star formation proceeds in a galactic disk or vice versa.
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This content will become publicly available on March 27, 2026
DIISC-VI (COS-DIISC): Ultraviolet Metal Absorption Relative to the H i Disk of Galaxies
Abstract As part of the Deciphering the Interplay between the Interstellar medium, Stars, and the Circumgalactic medium (DIISC) survey, we present the UV metal absorption features in the circumgalactic medium (CGM) near the Higas disk (<4.5RHI) of 31 nearby galaxies through quasar absorption-line spectroscopy. Of the ions under study, Siiiiλ1206 was most frequently detected (18 of 31 sight lines), while Ciiλ1334 and Siiiλ1260 were detected in 17 and 15 of 31 sight lines, respectively. Many components were consistent with photoionization equilibrium models; most of the cold and cool gas phase clouds were found to have lengths smaller than 2 kpc. Sight lines with smaller impact parameters (ρ) normalized by the galaxy’s virial radius (Rvir) and Hiradius (RHI) tend to have more components and larger rest-frame equivalent widths (Wr) than those that probe the CGM at larger radii. In particular, we find that the location of metals are better traced byρ/RHIrather than the traditionalρ/Rvir. Larger covering fractions are found closer to galaxies, with a radial decline that depends on theWrlimit used. Our results provide new insights into the spatial distribution of metals around the Hidisks of low-redshift galaxies.
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- Award ID(s):
- 2108159
- PAR ID:
- 10629204
- Publisher / Repository:
- Astrophysical Journal
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 982
- Issue:
- 2
- ISSN:
- 0004-637X
- Page Range / eLocation ID:
- 171
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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