{\it HST}/COS Observations of the Warm Ionized Gaseous Halo of NGC 891

Abstract

The metallicity of galactic gaseous halos provides insights into accretion and feedback of galaxies. The nearby edge-on galaxy NGC 891 has a multi-component gaseous halo and a background AGN (LQAC 035+042 003) projected 5 kpc above the disk near the minor axis. Against the UV continuum of this AGN, we detect lines from 13 ions associated with NGC 891 in new {\it HST}/COS spectra. Most of the absorption is from the warm ionized gas with $\log T=4.22\pm 0.04$, $\log n_{\mathrm{H}}=-1.26\pm 0.51$, and $\log N_{\mathrm{H}}=20.81\pm 0.20$. The metallicity of volatile elements (i.e., C, N, and S) is about half solar ($[X/H]\approx -0.3\pm 0.3$), while Mg, Fe, and Ni show lower metallicities of $[X/H]\approx -0.9$. The absorption system shows the depletion pattern seen for warm Galactic diffuse clouds, which is consistent with a mixture of ejected solar metallicity disk gases and the hot X-ray emitting halo ($Z=0.1-0.2Z_{\odot }$). The warm ionized gases are about 5 times more massive than the cold \ion{H}{1} emitting gases around the galactic center, which might lead to accretion with a mean rate of $10^2{M}_{\odot }\mathrm{y}{\mathrm{r}}^{-1}$ for a period of time. We also detect low metallicity ($\approx 0.1Z_{\odot }$) gases toward LQAC 035+042 003 at $110\mathrm{km}{\mathrm{s}}^{-1}$ (a high velocity cloud) and toward another sight line (3C 66A; 108 kpc projected from NGC 891) at $30\mathrm{km}{\mathrm{s}}^{-1}$. This low metallicity material could be the cold mode accretion from IGM or the tidal disruption of satellites in the NGC 891 halo.

17 pages, 9 figures, accepted by ApJ

References in corpus (13)

• Moving mesh cosmology: tracing cosmological gas accretion
• The cold gaseous halo of NGC 891
• The COS-Halos Survey: Metallicities in the Low-Redshift Circumgalactic Medium
• Effects of Supernova Feedback on the Formation of Galaxy Disks
• Distances to Galactic high-velocity clouds. I. Cohen Stream, complex GCP, cloud g1
• Quasars Probing Galaxies: I. Signatures of Gas Accretion at Redshift Approximately 0.2
• Probing the Fermi Bubbles in Ultraviolet Absorption: A Spectroscopic Signature of the Milky Way's Biconical Nuclear Outflow
• Low-metallicity Absorbers Account for Half of the Dense Circumgalactic Gas at z < 1
• Lopsided galaxies: the case of NGC 891
• Testing a Dynamical Equilibrium Model of the Extraplanar Diffuse Ionized Gas in NGC 891
• Ultraviolet Halos Around Spiral Galaxies. I. Morphology
• Infrared Spectroscopy of the Diffuse Ionized Halo of NGC 891
• A hot gaseous galaxy halo candidate with Mg X absorption

Cited by in corpus (5)

• Slicing the cool circumgalactic medium along the major-axis of a star-forming galaxy at $z=0.7$
• Detection of the diffuse HI emission in the Circumgalactic Medium of NGC 891 and NGC 4565
• Absorption Line Search Through Three Local Group Dwarf Galaxy Halos
• Census of Gaseous Satellites around Local Spiral Galaxies
• Disc-halo gas outflows driven by stellar clusters as seen in multiwavelength tracers