Disentangling the multiphase circumgalactic medium shared between a dwarf and a massive star-forming galaxy at z∼0.4

Abstract

The multi-phase circumgalactic medium (CGM) arises within the complex environment around a galaxy, or collection of galaxies, and possibly originates from a wide range of physical mechanisms. In this paper, we attempt to disentangle the origins of these multi-phase structures and present a detailed analysis of the quasar field Q0122−003 field using Keck/KCWI galaxy observations and HST/COS spectra probing the CGM. Our re-analysis of this field shows that there are two galaxies associated with the absorption. We have discovered a dwarf galaxy, G_27kpc (M⋆ = 108.7 M⊙), at z = 0.39863 that is 27 kpc from the quasar sightline. G_27kpc is only +21 km s−1 from a more massive (M⋆ = 1010.5 M⊙) star-forming galaxy, G_163kpc, at an impact parameter of 163 kpc. While G_163kpc is actively forming stars (SFR = 6.9 M⊙ yr−1), G_27kpc has a low star-formation rate (SFR = 0.08 ± 0.03 M⊙ yr−1) and star formation surface density (ΣSFR = 0.006 M⊙ kpc−2 yr−1), implying no active outflows. By comparing galaxy SFRs, kinematics, masses and distances from the quasar sightline to the absorption kinematics, column densities and metallicities, we have inferred the following: (1) Part of the low-ionization phase has a metallicity and kinematics consistent with being accreted onto G_27kpc. (2) The remainder of the low ionization phase has metallicities and kinematics consistent with being intragroup gas being transferred from G_27kpc to G_163kpc. (3) The high ionization phase is consistent with being produced solely by outflows originating from the massive halo of G_163kpc. Our results demonstrate the complex nature of the multi-phase CGM, especially around galaxy groups, and that detailed case-by-case studies are critical for disentangling its origins.

The Cosmic Ultraviolet Baryon Survey (CUBS) – IV. The complex multiphase circumgalactic medium as revealed by partial Lyman limit systems

“…Several recent works have demonstrated that many absorbers likely arise from complex galaxy structures and galaxy groups, not simply single galaxies evolving in isolation (Péroux et al 2019;Hamanowicz et al 2020;Chen et al 2020;Narayanan et al 2021). The high incidence of CGM gas within the virial halos of isolated dwarf galaxies (Johnson et al 2017), coupled with the recent identification of a dwarf galaxy at small projected separation from an absorber initially thought to be associated with a massive galaxy over 300 kpc away (Muzahid et al 2015;Nateghi et al 2021), highlights the need for deep galaxy spectroscopy to fully characterize the galactic environment, critical to understanding the true nature of CGM absorbers.…”

How Robust are the Inferred Density and Metallicity of the Circumgalactic Medium?

“…However note that, as long as a part of cloud assumed to have uniform density and metallicity irradiated with a UV background, uncertainties arising from UV background will be similar to the one presented here. For example, even for multi-phase gas as invoked in many studies (e.g, Pachat et al 2016Pachat et al , 2017Nateghi et al 2021;Haislmaier et al 2020), each phase will have similar uncertainty from UV background. Even with innovative techniques to models individual cloudlets as presented in Sameer et al (2021), each cloudlet and its phase will suffer with same uncertainty from UV background as long as a preferred UV background model is fixed for the inference.…”

Discovery of extremely low-metallicity circumgalactic gas at $z = 0.5$ toward Q0454-220

“…This term is related to the location above the mid-plane where the lagging halo velocity component begins to matter and 𝑣 los becomes dominated by an exponentially declining term. Following previous studies (e.g., Steidel et al 2002;Kacprzak et al 2010aKacprzak et al ,b, 2011bKacprzak et al , 2019French & Wakker 2020;Nateghi et al 2021) we are forcing the disc to be a thick, nearly-rigid rotator, where material far above the disc plane is rotating along with the disc. This places our low-and high-ionization clouds high above the galactic disc at a high angle.…”