Evolution of Cold Gas at 2 < z < 5: A Blind Search for H i and OH Absorption Lines toward Mid-infrared Color-selected Radio-loud AGN

Research output: Contribution to journalJournal articlepeer-review

Documents

  • N. Gupta
  • R. Srianand
  • G. Shukla
  • J-K Krogager
  • P. Noterdaeme
  • F. Combes
  • R. Dutta
  • Fynbo, Johan Peter Uldall
  • M. Hilton
  • E. Momjian
  • K. Moodley
  • P. Petitjean

We present results from a spectroscopically blind search for associated and intervening H i 21 cm and OH 18 cm absorption lines toward 88 active galactic nuclei (AGN) at 2 2. The detection rate ( 1.6(-1.4)(+3.8) %) suggests a low covering factor of the cold neutral medium (CNM; T similar to 100 K) associated with these powerful AGN. The intervening absorption line search, with a sensitivity to detect the CNM in damped Ly alpha systems (DLAs), has comoving absorption path lengths of Delta X = 130.1 and 167.7 for HI and OH, respectively. The corresponding number of absorbers per unit comoving path length are 2. Our AGN sample is optically fainter compared to the quasars used to search for DLAs in the past. In our optical spectra obtained using SALT and NOT, we detect five intervening (redshift path similar to 9.3) and two proximate DLAs. This is slightly excessive compared to the statistics based on optically selected quasars. The nondetection of H I 21 cm absorption from these DLAs suggests a small CNM covering fraction around galaxies at z > 2.

Original languageEnglish
Article number28
JournalAstrophysical Journal Supplement Series
Volume255
Issue number2
Number of pages21
ISSN0067-0049
DOIs
Publication statusPublished - Aug 2021

    Research areas

  • FOCUS IMAGING SPECTROGRAPH, AFRICAN LARGE TELESCOPE, LYMAN-ALPHA SYSTEMS, QUASAR-GALAXY PAIRS, DIGITAL SKY SURVEY, 21-CM ABSORPTION, CM ABSORPTION, NEUTRAL HYDROGEN, CENTIMETER ABSORPTION, INTERSTELLAR-MEDIUM

Links

ID: 276215239