A high signal-to-noise HST spectrum towards J1009+0713: precise absorption measurements in the CGM of two galaxies
Abstract
High signal-to-noise spectra towards background quasars are crucial for uncovering weak absorption in the circumgalactic medium (CGM) of intervening galaxies, such as the diagnostic lines of N V that provide insight to the ionization process of warm gas but typically have low equivalent widths. We present a new spectrum from the Hubble Space Telescope with a signal-to-noise ratio of ∼20-35 towards the quasar SDSS J1009+0713 and analyse absorption systems in the CGM of two L⋆ galaxies close to the line of sight. We identify additional absorption in the CGM of these galaxies that was not reported by the previous lower signal-to-noise spectrum, as well as Milky Way absorbers and quasar outflows from J1009+0713. We measure log (NN V/NO vi) ∼ -1.1 for two CGM absorbers, inconsistent with gas in collisional ionization equilibrium and consistent with a radiatively cooling bulk flow of ∼50-150 km s-1, which could be produced by galactic winds. These column density ratios are also consistent with those found for other L⋆ galaxies and for some gas in the Milky Way's halo. We place upper limits of log (NN V/NO VI) < -1.8 to -1.2 for other O VI absorbers in the same haloes, which suggests that O VI is produced by different processes in different parts of the CGM, even within the same galactic halo. Together with the kinematically different structure of high- and low-ionization lines, these results indicate there are many components to a single galaxy's gaseous halo. We find the redshift number density of Ly α forest absorbers and broad Ly α absorbers are consistent with expectations at this redshift.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- October 2019
- DOI:
- 10.1093/mnras/stz2108
- arXiv:
- arXiv:1809.09122
- Bibcode:
- 2019MNRAS.489...78L
- Keywords:
-
- galaxies: haloes;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 23 pages, 12 figures, 7 tables, accepted by MNRAS