ALMA plus VLT observations of a damped Lyman-$ absorbing galaxy::  massive, wide CO emission, gas-rich but with very low SFR

P. Møller; L. Christensen; M.~A. Zwaan; N. Kanekar; J.~X. Prochaska; Nils Henrik Rhodin; M. Dessauges-Zavadsky; Johan Peter Uldall Fynbo; M. Neeleman; T. Zafar

doi:10.1093/mnras/stx2845

ALMA plus VLT observations of a damped Lyman-$ absorbing galaxy: massive, wide CO emission, gas-rich but with very low SFR

P. Møller, L. Christensen, M.~A. Zwaan, N. Kanekar, J.~X. Prochaska, Nils Henrik Rhodin, M. Dessauges-Zavadsky, Johan Peter Uldall Fynbo, M. Neeleman, T. Zafar

15 Citations (Scopus)

Abstract

We are undertaking an Atacama Large Millimeter Array survey of molecular gas in galaxies selected for their strong HI absorption, so-called damped Lyα absorber (DLA)/sub- DLA galaxies. Here, we report CO(2-1) detection from a DLA galaxy at z = 0.716. We also present optical and near-infrared (NIR) spectra of the galaxy revealing [OII], Hα, and [N II] emission lines shifted by ~170 km s^-1 relative to the DLA, and providing an oxygen abundance 3.2 times solar, similar to the absorption metallicity. We report low unobscured SFR~1 M_⊙ yr^-1 given the large reservoir of molecular gas, and also modest obscured SFR = 4.5_-2.6^+4.4 M_⊙ yr^-1 based on far-IR and sub-millimetre data. We determine mass components of the galaxy: log[M*/M_⊙] = 10.80_-0.14^+0.07, log[M_mol-gas/M_⊙] = 10.37 ± 0.04, and log[M_dust/M_⊙] = 8.45_-0.30^+0.10. Surprisingly, this HI absorption-selected galaxy has no equivalent objects in CO surveys of flux-selected samples. The galaxy falls offcurrent scaling relations for the star formation rate (SFR) to molecular gas mass and CO Tully-Fisher relation. Detailed comparison of kinematical components of the absorbing, ionized, and molecular gas, combined with their spatial distribution, suggests that part of the CO gas is both kinematically and spatially decoupled from the main galaxy. It is thus possible that a major starburst in the past could explain the wide CO profile as well as the low SFR. Support for this also comes from the spectral energy distribution favouring an instantaneous burst of age ≈0.5 Gyr. Our survey will establish whether flux-selected surveys of molecular gas are missing a key stage in the evolution of galaxies and their conversion of gas to stars.

Original language	English
Journal	Monthly Notices of the Royal Astronomical Society
Volume	474
Pages (from-to)	4039-4055
Number of pages	17
ISSN	0035-8711
DOIs	https://doi.org/10.1093/mnras/stx2845
Publication status	Published - 1 Mar 2018

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Møller, P., Christensen, L., Zwaan, M. A., Kanekar, N., Prochaska, J. X., Rhodin, N. H., Dessauges-Zavadsky, M., Fynbo, J. P. U., Neeleman, M., & Zafar, T. (2018). ALMA plus VLT observations of a damped Lyman-$ absorbing galaxy: massive, wide CO emission, gas-rich but with very low SFR. Monthly Notices of the Royal Astronomical Society, 474, 4039-4055. https://doi.org/10.1093/mnras/stx2845

Møller, P, Christensen, L, Zwaan, MA, Kanekar, N, Prochaska, JX, Rhodin, NH, Dessauges-Zavadsky, M, Fynbo, JPU, Neeleman, M & Zafar, T 2018, 'ALMA plus VLT observations of a damped Lyman-$ absorbing galaxy: massive, wide CO emission, gas-rich but with very low SFR', Monthly Notices of the Royal Astronomical Society, vol. 474, pp. 4039-4055. https://doi.org/10.1093/mnras/stx2845

@article{b7767e7ffeeb495788822ac447faa4fa,

title = "ALMA plus VLT observations of a damped Lyman-$ absorbing galaxy:: massive, wide CO emission, gas-rich but with very low SFR",

abstract = "We are undertaking an Atacama Large Millimeter Array survey of molecular gas in galaxies selected for their strong HI absorption, so-called damped Lyα absorber (DLA)/sub- DLA galaxies. Here, we report CO(2-1) detection from a DLA galaxy at z = 0.716. We also present optical and near-infrared (NIR) spectra of the galaxy revealing [OII], Hα, and [N II] emission lines shifted by ~170 km s-1 relative to the DLA, and providing an oxygen abundance 3.2 times solar, similar to the absorption metallicity. We report low unobscured SFR~1 M⊙ yr-1 given the large reservoir of molecular gas, and also modest obscured SFR = 4.5-2.6+4.4 M⊙ yr-1 based on far-IR and sub-millimetre data. We determine mass components of the galaxy: log[M*/M⊙] = 10.80-0.14+0.07, log[Mmol-gas/M⊙] = 10.37 ± 0.04, and log[Mdust/M⊙] = 8.45-0.30+0.10. Surprisingly, this HI absorption-selected galaxy has no equivalent objects in CO surveys of flux-selected samples. The galaxy falls offcurrent scaling relations for the star formation rate (SFR) to molecular gas mass and CO Tully-Fisher relation. Detailed comparison of kinematical components of the absorbing, ionized, and molecular gas, combined with their spatial distribution, suggests that part of the CO gas is both kinematically and spatially decoupled from the main galaxy. It is thus possible that a major starburst in the past could explain the wide CO profile as well as the low SFR. Support for this also comes from the spectral energy distribution favouring an instantaneous burst of age ≈0.5 Gyr. Our survey will establish whether flux-selected surveys of molecular gas are missing a key stage in the evolution of galaxies and their conversion of gas to stars.",

keywords = "galaxies: abundances, galaxies: evolution, galaxies: formation, galaxies: high-redshift, galaxies: ISM",

author = "P. M{\o}ller and L. Christensen and M.~A. Zwaan and N. Kanekar and J.~X. Prochaska and Rhodin, {Nils Henrik} and M. Dessauges-Zavadsky and Fynbo, {Johan Peter Uldall} and M. Neeleman and T. Zafar",

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doi = "10.1093/mnras/stx2845",

language = "English",

volume = "474",

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TY - JOUR

T1 - ALMA plus VLT observations of a damped Lyman-$ absorbing galaxy:

T2 - massive, wide CO emission, gas-rich but with very low SFR

AU - Møller, P.

AU - Christensen, L.

AU - Zwaan, M.~A.

AU - Kanekar, N.

AU - Prochaska, J.~X.

AU - Rhodin, Nils Henrik

AU - Dessauges-Zavadsky, M.

AU - Fynbo, Johan Peter Uldall

AU - Neeleman, M.

AU - Zafar, T.

PY - 2018/3/1

Y1 - 2018/3/1

N2 - We are undertaking an Atacama Large Millimeter Array survey of molecular gas in galaxies selected for their strong HI absorption, so-called damped Lyα absorber (DLA)/sub- DLA galaxies. Here, we report CO(2-1) detection from a DLA galaxy at z = 0.716. We also present optical and near-infrared (NIR) spectra of the galaxy revealing [OII], Hα, and [N II] emission lines shifted by ~170 km s-1 relative to the DLA, and providing an oxygen abundance 3.2 times solar, similar to the absorption metallicity. We report low unobscured SFR~1 M⊙ yr-1 given the large reservoir of molecular gas, and also modest obscured SFR = 4.5-2.6+4.4 M⊙ yr-1 based on far-IR and sub-millimetre data. We determine mass components of the galaxy: log[M*/M⊙] = 10.80-0.14+0.07, log[Mmol-gas/M⊙] = 10.37 ± 0.04, and log[Mdust/M⊙] = 8.45-0.30+0.10. Surprisingly, this HI absorption-selected galaxy has no equivalent objects in CO surveys of flux-selected samples. The galaxy falls offcurrent scaling relations for the star formation rate (SFR) to molecular gas mass and CO Tully-Fisher relation. Detailed comparison of kinematical components of the absorbing, ionized, and molecular gas, combined with their spatial distribution, suggests that part of the CO gas is both kinematically and spatially decoupled from the main galaxy. It is thus possible that a major starburst in the past could explain the wide CO profile as well as the low SFR. Support for this also comes from the spectral energy distribution favouring an instantaneous burst of age ≈0.5 Gyr. Our survey will establish whether flux-selected surveys of molecular gas are missing a key stage in the evolution of galaxies and their conversion of gas to stars.

AB - We are undertaking an Atacama Large Millimeter Array survey of molecular gas in galaxies selected for their strong HI absorption, so-called damped Lyα absorber (DLA)/sub- DLA galaxies. Here, we report CO(2-1) detection from a DLA galaxy at z = 0.716. We also present optical and near-infrared (NIR) spectra of the galaxy revealing [OII], Hα, and [N II] emission lines shifted by ~170 km s-1 relative to the DLA, and providing an oxygen abundance 3.2 times solar, similar to the absorption metallicity. We report low unobscured SFR~1 M⊙ yr-1 given the large reservoir of molecular gas, and also modest obscured SFR = 4.5-2.6+4.4 M⊙ yr-1 based on far-IR and sub-millimetre data. We determine mass components of the galaxy: log[M*/M⊙] = 10.80-0.14+0.07, log[Mmol-gas/M⊙] = 10.37 ± 0.04, and log[Mdust/M⊙] = 8.45-0.30+0.10. Surprisingly, this HI absorption-selected galaxy has no equivalent objects in CO surveys of flux-selected samples. The galaxy falls offcurrent scaling relations for the star formation rate (SFR) to molecular gas mass and CO Tully-Fisher relation. Detailed comparison of kinematical components of the absorbing, ionized, and molecular gas, combined with their spatial distribution, suggests that part of the CO gas is both kinematically and spatially decoupled from the main galaxy. It is thus possible that a major starburst in the past could explain the wide CO profile as well as the low SFR. Support for this also comes from the spectral energy distribution favouring an instantaneous burst of age ≈0.5 Gyr. Our survey will establish whether flux-selected surveys of molecular gas are missing a key stage in the evolution of galaxies and their conversion of gas to stars.

KW - galaxies: abundances, galaxies: evolution, galaxies: formation, galaxies: high-redshift, galaxies: ISM

U2 - 10.1093/mnras/stx2845

DO - 10.1093/mnras/stx2845

M3 - Journal article

SN - 0035-8711

VL - 474

SP - 4039

EP - 4055

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

ER -

ALMA plus VLT observations of a damped Lyman-$ absorbing galaxy: massive, wide CO emission, gas-rich but with very low SFR

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