FLASH Early Science – discovery of an intervening HI 21-cm absorber from an ASKAP survey of the GAMA 23 field

J R Allison; E M Sadler; S Bellstedt; L J M Davies; S P Driver; S L Ellison; M Huynh; A D Kapińska; E K Mahony; V A Moss; A S G Robotham; M T Whiting; S J Curran; J Darling; A W Hotan; R W Hunstead; B S Koribalski; C D P Lagos; M Pettini; K A Pimbblet; M A Voronkov

doi:10.1093/mnras/staa949

FLASH Early Science – discovery of an intervening HI 21-cm absorber from an ASKAP survey of the GAMA 23 field

J R Allison, E M Sadler, S Bellstedt, L J M Davies, S P Driver, S L Ellison, M Huynh, A D Kapińska, E K Mahony, V A Moss, A S G Robotham, M T Whiting, S J Curran, J Darling, A W Hotan, R W Hunstead, B S Koribalski, C D P Lagos, M Pettini, K A PimbbletM A Voronkov

School of Physics and Astronomy

Research output: Contribution to journal › Article › peer-review

Abstract

We present early science results from the First Large Absorption Survey in H i (FLASH), a spectroscopically blind survey for 21-cm absorption lines in cold hydrogen (H i) gas at cosmological distances using the Australian Square Kilometre Array Pathfinder (ASKAP). We have searched for H i absorption towards 1253 radio sources in the GAMA 23 field, covering redshifts between z = 0.34 and 0.79 over a sky area of approximately 50 deg². In a purely blind search, we did not obtain any detections of 21-cm absorbers above our reliability threshold. Assuming a fiducial value for the H i spin temperature of T_spin = 100 K and source covering fraction c_f = 1, the total comoving absorption path-length sensitive to all Damped Lyman α Absorbers (DLAs; N_H i ≥ 2 × 10²⁰ cm⁻²) is ΔX = 6.6 ± 0.3 (Δz = 3.7 ± 0.2) and super-DLAs (N_H i ≥ 2 × 10²¹ cm⁻²) is ΔX = 111 ± 6 (Δz= 63 ± 3). We estimate upper limits on the H i column density frequency distribution function that are consistent with measurements from prior surveys for redshifted optical DLAs, and nearby 21-cm emission and absorption. By cross-matching our sample of radio sources with optical spectroscopic identifications of galaxies in the GAMA 23 field, we were able to detect 21-cm absorption at z = 0.3562 towards NVSS J224500−343030, with a column density of NHI=(1.2±0.1)×1020(Tspin/100K) cm⁻². The absorber is associated with GAMA J22450.05−343031.7, a massive early-type galaxy at an impact parameter of 17 kpc with respect to the radio source and which may contain a massive (M_H i ≳ 3 × 10⁹ M_⊙) gas disc. Such gas-rich early types are rare, but have been detected in the nearby Universe.

Original language	English
Pages (from-to)	3627-3641
Journal	Monthly Notices of the Royal Astronomical Society
Volume	494
Issue number	3
Early online date	9 Apr 2020
DOIs	https://doi.org/10.1093/mnras/staa949
Publication status	Published - May 2020

Keywords

Galaxies: evolution
Galaxies: high redshift
Galaxies: ISM
Galaxies: strucutre
Radio: lines galaxies

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10.1093/mnras/staa949

Allison_2020_MNRAS_FLASH_AAM
Copyright © 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This work has been made available online in accordance with publisher policies or with permission. Permission for further reuse of this content should be sought from the publisher or the rights holder. This is the author created accepted manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at https://doi.org/10.1093/mnras/staa949
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Allison, J. R., Sadler, E. M., Bellstedt, S., Davies, L. J. M., Driver, S. P., Ellison, S. L., Huynh, M., Kapińska, A. D., Mahony, E. K., Moss, V. A., Robotham, A. S. G., Whiting, M. T., Curran, S. J., Darling, J., Hotan, A. W., Hunstead, R. W., Koribalski, B. S., Lagos, C. D. P., Pettini, M., ... Voronkov, M. A. (2020). FLASH Early Science – discovery of an intervening HI 21-cm absorber from an ASKAP survey of the GAMA 23 field. Monthly Notices of the Royal Astronomical Society, 494(3), 3627-3641. https://doi.org/10.1093/mnras/staa949

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title = "FLASH Early Science – discovery of an intervening HI 21-cm absorber from an ASKAP survey of the GAMA 23 field",

abstract = "We present early science results from the First Large Absorption Survey in H i (FLASH), a spectroscopically blind survey for 21-cm absorption lines in cold hydrogen (H i) gas at cosmological distances using the Australian Square Kilometre Array Pathfinder (ASKAP). We have searched for H i absorption towards 1253 radio sources in the GAMA 23 field, covering redshifts between z = 0.34 and 0.79 over a sky area of approximately 50 deg2. In a purely blind search, we did not obtain any detections of 21-cm absorbers above our reliability threshold. Assuming a fiducial value for the H i spin temperature of Tspin = 100 K and source covering fraction cf = 1, the total comoving absorption path-length sensitive to all Damped Lyman α Absorbers (DLAs; NH i ≥ 2 × 1020 cm−2) is ΔX = 6.6 ± 0.3 (Δz = 3.7 ± 0.2) and super-DLAs (NH i ≥ 2 × 1021 cm−2) is ΔX = 111 ± 6 (Δz= 63 ± 3). We estimate upper limits on the H i column density frequency distribution function that are consistent with measurements from prior surveys for redshifted optical DLAs, and nearby 21-cm emission and absorption. By cross-matching our sample of radio sources with optical spectroscopic identifications of galaxies in the GAMA 23 field, we were able to detect 21-cm absorption at z = 0.3562 towards NVSS J224500−343030, with a column density of NHI=(1.2±0.1)×1020(Tspin/100K) cm−2. The absorber is associated with GAMA J22450.05−343031.7, a massive early-type galaxy at an impact parameter of 17 kpc with respect to the radio source and which may contain a massive (MH i ≳ 3 × 109 M⊙) gas disc. Such gas-rich early types are rare, but have been detected in the nearby Universe.",

keywords = "Galaxies: evolution, Galaxies: high redshift, Galaxies: ISM, Galaxies: strucutre, Radio: lines galaxies",

author = "Allison, {J R} and Sadler, {E M} and S Bellstedt and Davies, {L J M} and Driver, {S P} and Ellison, {S L} and M Huynh and Kapi{\'n}ska, {A D} and Mahony, {E K} and Moss, {V A} and Robotham, {A S G} and Whiting, {M T} and Curran, {S J} and J Darling and Hotan, {A W} and Hunstead, {R W} and Koribalski, {B S} and Lagos, {C D P} and M Pettini and Pimbblet, {K A} and Voronkov, {M A}",

year = "2020",

month = may,

doi = "10.1093/mnras/staa949",

language = "English",

volume = "494",

pages = "3627--3641",

journal = "Monthly Notices of the Royal Astronomical Society",

issn = "0035-8711",

publisher = "Oxford University Press",

number = "3",

}

Allison, JR, Sadler, EM, Bellstedt, S, Davies, LJM, Driver, SP, Ellison, SL, Huynh, M, Kapińska, AD, Mahony, EK, Moss, VA, Robotham, ASG, Whiting, MT, Curran, SJ, Darling, J, Hotan, AW, Hunstead, RW, Koribalski, BS, Lagos, CDP, Pettini, M, Pimbblet, KA & Voronkov, MA 2020, 'FLASH Early Science – discovery of an intervening HI 21-cm absorber from an ASKAP survey of the GAMA 23 field', Monthly Notices of the Royal Astronomical Society, vol. 494, no. 3, pp. 3627-3641. https://doi.org/10.1093/mnras/staa949

TY - JOUR

T1 - FLASH Early Science – discovery of an intervening HI 21-cm absorber from an ASKAP survey of the GAMA 23 field

AU - Allison, J R

AU - Sadler, E M

AU - Bellstedt, S

AU - Davies, L J M

AU - Driver, S P

AU - Ellison, S L

AU - Huynh, M

AU - Kapińska, A D

AU - Mahony, E K

AU - Moss, V A

AU - Robotham, A S G

AU - Whiting, M T

AU - Curran, S J

AU - Darling, J

AU - Hotan, A W

AU - Hunstead, R W

AU - Koribalski, B S

AU - Lagos, C D P

AU - Pettini, M

AU - Pimbblet, K A

AU - Voronkov, M A

PY - 2020/5

Y1 - 2020/5

N2 - We present early science results from the First Large Absorption Survey in H i (FLASH), a spectroscopically blind survey for 21-cm absorption lines in cold hydrogen (H i) gas at cosmological distances using the Australian Square Kilometre Array Pathfinder (ASKAP). We have searched for H i absorption towards 1253 radio sources in the GAMA 23 field, covering redshifts between z = 0.34 and 0.79 over a sky area of approximately 50 deg2. In a purely blind search, we did not obtain any detections of 21-cm absorbers above our reliability threshold. Assuming a fiducial value for the H i spin temperature of Tspin = 100 K and source covering fraction cf = 1, the total comoving absorption path-length sensitive to all Damped Lyman α Absorbers (DLAs; NH i ≥ 2 × 1020 cm−2) is ΔX = 6.6 ± 0.3 (Δz = 3.7 ± 0.2) and super-DLAs (NH i ≥ 2 × 1021 cm−2) is ΔX = 111 ± 6 (Δz= 63 ± 3). We estimate upper limits on the H i column density frequency distribution function that are consistent with measurements from prior surveys for redshifted optical DLAs, and nearby 21-cm emission and absorption. By cross-matching our sample of radio sources with optical spectroscopic identifications of galaxies in the GAMA 23 field, we were able to detect 21-cm absorption at z = 0.3562 towards NVSS J224500−343030, with a column density of NHI=(1.2±0.1)×1020(Tspin/100K) cm−2. The absorber is associated with GAMA J22450.05−343031.7, a massive early-type galaxy at an impact parameter of 17 kpc with respect to the radio source and which may contain a massive (MH i ≳ 3 × 109 M⊙) gas disc. Such gas-rich early types are rare, but have been detected in the nearby Universe.

AB - We present early science results from the First Large Absorption Survey in H i (FLASH), a spectroscopically blind survey for 21-cm absorption lines in cold hydrogen (H i) gas at cosmological distances using the Australian Square Kilometre Array Pathfinder (ASKAP). We have searched for H i absorption towards 1253 radio sources in the GAMA 23 field, covering redshifts between z = 0.34 and 0.79 over a sky area of approximately 50 deg2. In a purely blind search, we did not obtain any detections of 21-cm absorbers above our reliability threshold. Assuming a fiducial value for the H i spin temperature of Tspin = 100 K and source covering fraction cf = 1, the total comoving absorption path-length sensitive to all Damped Lyman α Absorbers (DLAs; NH i ≥ 2 × 1020 cm−2) is ΔX = 6.6 ± 0.3 (Δz = 3.7 ± 0.2) and super-DLAs (NH i ≥ 2 × 1021 cm−2) is ΔX = 111 ± 6 (Δz= 63 ± 3). We estimate upper limits on the H i column density frequency distribution function that are consistent with measurements from prior surveys for redshifted optical DLAs, and nearby 21-cm emission and absorption. By cross-matching our sample of radio sources with optical spectroscopic identifications of galaxies in the GAMA 23 field, we were able to detect 21-cm absorption at z = 0.3562 towards NVSS J224500−343030, with a column density of NHI=(1.2±0.1)×1020(Tspin/100K) cm−2. The absorber is associated with GAMA J22450.05−343031.7, a massive early-type galaxy at an impact parameter of 17 kpc with respect to the radio source and which may contain a massive (MH i ≳ 3 × 109 M⊙) gas disc. Such gas-rich early types are rare, but have been detected in the nearby Universe.

KW - Galaxies: evolution

KW - Galaxies: high redshift

KW - Galaxies: ISM

KW - Galaxies: strucutre

KW - Radio: lines galaxies

UR - https://arxiv.org/abs/2004.00847

U2 - 10.1093/mnras/staa949

DO - 10.1093/mnras/staa949

M3 - Article

SN - 0035-8711

VL - 494

SP - 3627

EP - 3641

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

IS - 3

ER -

FLASH Early Science – discovery of an intervening HI 21-cm absorber from an ASKAP survey of the GAMA 23 field

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