Details

Autor(en) / Beteiligte

• Mahony, Elizabeth K
• Allison, James R
• Sadler, Elaine M
• Ellison, Sara L
• Mao, Sui Ann
• Morganti, Raffaella
• Moss, Vanessa A
• Seta, Amit
• Tadhunter, Clive N
• Weng, Simon
• Whiting, Matthew T
• Yoon, Hyein
• Bell, Martin
• Bunton, John D
• Harvey-Smith, Lisa
• Kimball, Amy
• Koribalski, Bärbel S
• Voronkov, Max A

Titel

H i absorption at z ∼ 0.7 against the lobe of the powerful radio galaxy PKS 0409−75

Ist Teil von

• Monthly notices of the Royal Astronomical Society, 2021-11, Vol.509 (2), p.1690-1702

Ort / Verlag

Oxford University Press

Erscheinungsjahr

2021

Quelle

EZB Electronic Journals Library

Beschreibungen/Notizen

• ABSTRACT We present results from a search for the H i 21-cm line in absorption towards 16 bright radio sources with the six-antenna commissioning array of the Australian Square Kilometre Array Pathfinder. Our targets were selected from the 2-Jy sample, a flux-limited survey of the southern radio sky with extensive multiwavelength follow-up. Two sources were detected in H i absorption including a new detection towards the bright Fanaroff–Riley Type II radio galaxy PKS 0409−75 at a redshift of $z$ = 0.674. The H i absorption line is blueshifted by ∼3300 km s−1 compared to the optical redshift of the host galaxy of PKS 0409−75 at $z$ = 0.693. Deep optical imaging and spectroscopic follow-up with the GMOS instrument on the Gemini-South telescope reveal that the H i absorption is associated with a galaxy in front of the southern radio lobe with a stellar mass of 3.2–6.8 × 1011 M⊙, a star formation rate of ∼1.24 M⊙ yr−1, and an estimated H i column density of 2.16 × 1021 cm−2, assuming a spin temperature of Tspin = 500 K and source covering factor of Cf = 0.3. Using polarization measurements of PKS 0409−75 from the literature, we estimate the magnetic field of the absorbing galaxy to be ∼14.5 $\mu$G, consistent with field strengths observed in nearby spiral galaxies but larger than expected for an elliptical galaxy. Results from this pilot study can inform future surveys as new wide-field telescopes allow us to search for 21-cm H i absorption towards all bright radio sources as opposed to smaller targeted samples.