| Name: Sumukha R Bharadwaj |
| Affiliation: Indian Institute of Space Science and Technology, Thiruvananthapuram |
| Conference ID: ASI2026_995 |
| Title: A Partial Lyman Limit Intervening Absorber Tracing Cold Mode Accretion |
| Abstract Type: Poster |
| Abstract Category: Galaxies and Cosmology |
| Author(s) and Co-Author(s) with Affiliation: Sumukha R Bharadwaj(Indian Institute of Space Science and Technology), Anand Narayanan(Indian Institute of Space Science and Technology) |
| Abstract: We present a detailed analysis of a partial Lyman limit system at $z = 0.87641$ detected in the \textit{HST}/COS spectrum of the background quasar LBQS~0107$-$0235. The absorber exhibits a simple kinematic structure, with the metal-lines and the H\,\textsc{i} Lyman-series absorption well described by a single component. Photoionization modeling yields a gas metallicity of one-tenth solar and a hydrogen number density of $n_{\mathrm{H}} = 7.8 \times 10^{-4}~\mathrm{cm}^{-3}$. At the absorber redshift, the $VLT$/MUSE data show two galaxies (G1 and G2) at normalized impact parameters of $\rho / R_{\mathrm{vir}} \approx 0.9$ and velocity separations of $|\Delta v| = 18$ and $99~\mathrm{km~s^{-1}}$, respectively, from the absorber. Both galaxies have rotating disks with stellar masses of $M_{*} \approx 6\times10^{9}$ and $\sim 2.2 \times10^{10}~\mathrm{M}_{\odot}$, and star formation rates of $\approx 2.5$ and $2.2~\mathrm{M}_{\odot}~\mathrm{yr}^{-1}$, placing them within the star-forming main sequence at this redshift. The absorber is positioned very close to the projected major axis of both galaxies. The galaxy properties along with the absorber's characteristics agree with tracing a metal-poor inflowing stream. This interpretation is consistent with cosmological simulations in which cold-mode accretion provides the dominant fuel for star formation in galaxies in halos of mass $M_{\mathrm{h}} \lesssim 10^{12}~\mathrm{M}_{\odot}$.
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