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Abstract The Ovi1032, 1038 Å line is a key probe of cooling gas in the circumgalactic medium (CGM) of galaxies but has been observed to date primarily in absorption along single sight lines. We present deep Hubble Space Telescope (HST) Solar Blind Channel of the Advanced Camera for Surveys observations of the compact, massive starburst Makani. Makani hosts a 100 kpc, [Oii]-emitting galactic wind driven by two episodes of star formation over 400 Myr. We detect Oviand Lyαemission across the [Oii] nebula with similar morphology and extent, out tor≈ 50 kpc. Using differential narrowband imaging, we separate Lyαand Oviand show that the Oviemission is comparable in brightness to [Oii], withLO VI= 4 × 1042erg s−1. The similar hourglass morphology and size of [Oii] and Oviimplicate radiative cooling atT= 105.5K in a hot–cold interface. This may occur as theT> 107K CGM—or the hot fluid driving the wind—exchanges mass with theT≈ 104K clouds entrained in (or formed by) the wind. The optical/UV line ratios may be consistent with shock ionization, although uncertain attenuation and Lyαradiative transfer complicate the interpretation. The detection of Oviin Makani lies at the bleeding edge of the UV imaging capabilities of HST and provides a benchmark for future emission-line imaging of the CGM with a wide-area UV telescope.
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This content will become publicly available on April 24, 2027
Modelling emission-line surface brightness in a multiphase galactic wind: an O vi case study
ABSTRACT We present a fast and robust analytic framework for predicting surface brightness (SB) of emission lines in galactic winds as a function of radius up to $$\sim 100$$ kpc out in the circum-galactic medium. We model multiphase structure in galactic winds by capturing emission from both the volume-filling hot phase (T $$\sim 10^{6-7}$$ K) and turbulent radiative mixing layers that host intermediate temperature gas at the boundaries of cold clouds (T $$\sim 10^4$$ K). Our multiphase framework makes significantly different predictions of emission signatures compared to traditional single-phase models and explains the paucity of O vi SB measurements in the literature. After accounting for ram pressure equilibrium between the cold clouds and hot wind in supersonic outflows, non-equilibrium ionization effects, and energy budgets other than mechanical energy from core-collapse supernovae, our O vi SB predictions qualitatively match observational results. Our framework provides constraints on the optimal galactic wind properties that facilitate O vi emission observations, including star formation rate surface density, hot phase mass loading factor, and thermalization efficiency factor. These constraints are consistent with existing observations and can help inform future target selections.
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- Award ID(s):
- 2601424
- PAR ID:
- 10710755
- Publisher / Repository:
- MNRAS
- Date Published:
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 548
- Issue:
- 3
- ISSN:
- 0035-8711
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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