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

Mahony, EK; Allison, JR; Sadler, EM; Ellison, SL; Mao, SA; Morganti, R; Moss, VA; Seta, A; Tadhunter, CN; Weng, S; Whiting, MT; Yoon, H; Bell, M; Bunton, JD; Harvey-Smith, L; Kimball, A; Koribalski, BS; Voronkov, MA

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

Mahony, EK Allison, JR Sadler, EM Ellison, SL Mao, SA Morganti, R Moss, VA Seta, A Tadhunter, CN Weng, S Whiting, MT Yoon, H Bell, M

Bunton, JD Harvey-Smith, L Kimball, A Koribalski, BS Voronkov, MA

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Publisher:: Royal Astronomical Society
Publication Type:: Journal Article
Citation:: Monthly Notices of the Royal Astronomical Society, 2022, 509, (2), pp. 1690-1702
Issue Date:: 2022-01-01

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Field	Value	Language
dc.contributor.author	Mahony, EK
dc.contributor.author	Allison, JR
dc.contributor.author	Sadler, EM
dc.contributor.author	Ellison, SL
dc.contributor.author	Mao, SA
dc.contributor.author	Morganti, R
dc.contributor.author	Moss, VA
dc.contributor.author	Seta, A
dc.contributor.author	Tadhunter, CN
dc.contributor.author	Weng, S
dc.contributor.author	Whiting, MT
dc.contributor.author	Yoon, H
dc.contributor.author	Bell, M https://orcid.org/0000-0003-1767-5277
dc.contributor.author	Bunton, JD
dc.contributor.author	Harvey-Smith, L
dc.contributor.author	Kimball, A
dc.contributor.author	Koribalski, BS
dc.contributor.author	Voronkov, MA
dc.date.accessioned	2022-11-08T01:35:03Z
dc.date.available	2022-11-08T01:35:03Z
dc.date.issued	2022-01-01
dc.identifier.citation	Monthly Notices of the Royal Astronomical Society, 2022, 509, (2), pp. 1690-1702
dc.identifier.issn	0035-8711
dc.identifier.issn	1365-2966
dc.identifier.uri	http://hdl.handle.net/10453/163295
dc.description.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 μG, 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.
dc.language	en
dc.publisher	Royal Astronomical Society
dc.relation.ispartof	Monthly Notices of the Royal Astronomical Society
dc.relation.isbasedon	10.1093/mnras/stab3041
dc.rights	info:eu-repo/semantics/openAccess
dc.subject	0201 Astronomical and Space Sciences
dc.subject.classification	Astronomy & Astrophysics
dc.title	H i absorption at z ∼ 0.7 against the lobe of the powerful radio galaxy PKS 0409−75
dc.type	Journal Article
utslib.citation.volume	509
utslib.for	0201 Astronomical and Space Sciences
pubs.organisational-group	/University of Technology Sydney
pubs.organisational-group	/University of Technology Sydney/Faculty of Science
pubs.organisational-group	/University of Technology Sydney/Faculty of Science/School of Mathematical and Physical Sciences
utslib.copyright.status	open_access	*
pubs.consider-herdc	false
dc.date.updated	2022-11-08T01:35:01Z
pubs.issue	2
pubs.publication-status	Published
pubs.volume	509
utslib.citation.issue	2

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 μG, 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.

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http://hdl.handle.net/10453/163295