2020/11/25 by Jens-Kristian Krogager, Pasquier Noterdaeme, P. Noterdaeme
Physics and Astronomy · #Absorption (acoustics) #Astrophysics #Astrophysics and Star Formation Studies #Galaxies: Formation, Evolution, Phenomena #Galaxy #Halo #Interstellar medium #Optics #Physics #Redshift #Stellar, planetary, and galactic studies #astro-ph.GA
paper · pdf · doi:10.1051/0004-6361/202039843
A&A Letter, 5 pages (incl. 2 page auxiliary data table). Updated to reflect published version
openalex publication_date 2020/11/25 · arxiv created 2020/11/27 · openalex created_date 2020/12/07 · arxiv updated 2020/12/16 · openalex updated_date 2026/08/06
We present a statistical model of the selection function of cold neutral gas in high-redshift ( z = 2.5) absorption systems. The model is based on the canonical two-phase model of the neutral gas in the interstellar medium and contains only one parameter for which we do not have direct observational priors: namely the central pressure of an L * halo at z = 2.5, P * . Using observations of the fraction of cold gas absorption in strong H I -selected absorbers, we were able to constrain P * . The model simultaneously reproduces the column density distributions of H I and H 2 , and we derived an expected total incidence of cold gas at z ∼ 2.5 of l CNM = 12 × 10 −3 . Compared to recent measurements of the incidence of C I -selected absorbers (EW λ 1560 > 0.4 Å), the value of l CNM from our model indicates that only 15% of the total cold gas would lead to strong C I absorption (EW > 0.4 Å). Nevertheless, C I lines are extremely useful probes of the cold gas as they are relatively easy to detect and provide direct constraints on the physical conditions. Lastly, our model self-consistently reproduces the fraction of cold gas absorbers as a function of N H I .