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SUMMARY:Search for 21-cm absorption systems with CHIME
DTSTART;VALUE=DATE-TIME:20261028T180500Z
DTEND;VALUE=DATE-TIME:20261028T181500Z
DTSTAMP;VALUE=DATE-TIME:20261026T232743Z
UID:indico-contribution-3668@nyx.physics.mcgill.ca
DESCRIPTION:Speakers: Arash Mirhosseini (Dunlap Institute for Astronomy & 
 Astrophysics\, University of Toronto)\nNeutral atomic hydrogen is the prim
 ary raw material from which stars form in galaxies\; and understanding its
  spatial distribution\, kinematics\, and thermal state across cosmic time 
 is therefore fundamental to our comprehension of how galaxies assemble and
  evolve. The 21-cm hyperfine transition of neutral hydrogen is a powerful 
 probe of cold gas in and around galaxies across cosmic time. When a radio 
 source lies behind a cloud of neutral hydrogen\, the cold gas imprints a c
 haracteristic absorption feature in the spectrum of the background source 
 at the redshifted 21-cm frequency. Unlike 21-cm emission\, the absorption 
 feature is detectable independently of the distance to the absorber\, so i
 ts detectability does not diminish with redshift. Despite this advantage\,
  the known sample of extragalactic 21-cm absorbers at redshifts z > 1 has 
 remained small: only 42 systems were known prior to this work\, reflecting
  the scarcity of suitable radio facilities at the relevant frequencies.\n\
 nIn this talk\, I present the results of a pilot blind search for 21-cm ab
 sorption systems conducted with the Canadian Hydrogen Intensity Mapping Ex
 periment (CHIME)\, a radio telescope operating between 400 and 800 MHz\, w
 hich corresponds to the 21-cm line at redshifts 0.78 < z < 2.55. This pilo
 t survey resulted in the discovery of a new 21-cm absorber at z = 2.327\, 
 which is only the fifth known absorber associated with a quasar at z > 2. 
 The survey also recovered two previously known intervening absorbers\, val
 idating the detection pipeline.\n\nhttps://nyx.physics.mcgill.ca/event/587
 /contributions/3668/
LOCATION:Online 
URL:https://nyx.physics.mcgill.ca/event/587/contributions/3668/
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