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ALMACAL – III. A combined ALMA and MUSE survey for neutral, molecular, and ionized gas in an H i-absorption-selected system.

Klitsch, A. and Péroux, C. and Zwaan, M. A. and Smail, I. and Oteo, I. and Biggs, A. D. and Popping, G. and Swinbank, A. M. (2018) 'ALMACAL – III. A combined ALMA and MUSE survey for neutral, molecular, and ionized gas in an H i-absorption-selected system.', Monthly notices of the Royal Astronomical Society., 475 (1). pp. 492-507.


Studying the flow of baryons into and out of galaxies is an important part of understanding the evolution of galaxies over time. We present a detailed case study of the environment around an intervening Ly α absorption line system at zabs = 0.633, seen towards the quasar J0423−0130 (zQSO = 0.915). We detect with ALMA the 12CO(2–1), 12CO(3–2), and 1.2 mm continuum emission from a galaxy at the redshift of the Ly α absorber at a projected distance of 135 kpc. From the ALMA detections, we infer interstellar medium conditions similar to those in low-redshift luminous infrared galaxies. Director's Discretionary Time (DDT) Multi-Unit Spectroscopic Explorer (MUSE) integral field unit observations reveal the optical counterpart of the 12CO emission line source and three additional emission line galaxies at the absorber redshift, which together form a galaxy group. The 12CO emission line detections originate from the most massive galaxy in this group. While we cannot exclude that we miss a fainter host, we reach a dust-uncorrected star formation rate (SFR) limit of >0.3 M⊙yr−1 within 100 kpc from the sightline to the background quasar. We measure the dust-corrected SFR (ranging from 3 to 50 M⊙ yr−1), the morpho-kinematics and the metallicities of the four group galaxies to understand the relation between the group and the neutral gas probed in absorption. We find that the Ly α absorber traces either an outflow from the most massive galaxy or intragroup gas. This case study illustrates the power of combining ALMA and MUSE to obtain a census of the cool baryons in a bounded structure at intermediate redshift.

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Publisher statement:This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2017 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Date accepted:27 November 2017
Date deposited:16 February 2018
Date of first online publication:09 December 2017
Date first made open access:16 February 2018

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