Resolving the ISM at the Peak of Cosmic Star Formation with ALMA: The Distribution of CO and Dust Continuum in z ∼ 2.5 Submillimeter Galaxies

Rivera, Gabriela Calistro; Hodge, J.A.; Smail, Ian; Swinbank, A.M.; Weiss, A.; Wardlow, J.L.; Walter, F.; Rybak, M.; Chen, Chian-Chou; Brandt, W.N.; Coppin, K.; Cunha, E. da; Dannerbauer, H.; Greve, T.R.; Karim, A.; Knudsen, K.K.; Schinnerer, E.; Simpson, J.M.; Venemans, B.; Werf, P.P. van der

doi:10.3847/1538-4357/aacffa

Resolving the ISM at the Peak of Cosmic Star Formation with ALMA: The Distribution of CO and Dust Continuum in z ∼ 2.5 Submillimeter Galaxies

Rivera, Gabriela Calistro; Hodge, J.A.; Smail, Ian; Swinbank, A.M.; Weiss, A.; Wardlow, J.L.; Walter, F.; Rybak, M.; Chen, Chian-Chou; Brandt, W.N.; Coppin, K.; Cunha, E. da; Dannerbauer, H.; Greve, T.R.; Karim, A.; Knudsen, K.K.; Schinnerer, E.; Simpson, J.M.; Venemans, B.; Werf, P.P. van der

Authors

Gabriela Calistro Rivera

J.A. Hodge

Professor Ian Smail ian.smail@durham.ac.uk
Emeritus Professor

Professor Mark Swinbank a.m.swinbank@durham.ac.uk
Professor

A. Weiss

J.L. Wardlow

F. Walter

M. Rybak

Chian-Chou Chen

W.N. Brandt

K. Coppin

E. da Cunha

H. Dannerbauer

T.R. Greve

A. Karim

K.K. Knudsen

E. Schinnerer

J.M. Simpson

B. Venemans

P.P. van der Werf

Abstract

We use Atacama Large Millimeter Array (ALMA) observations of four submillimeter galaxies (SMGs) at z ~ 2–3 to investigate the spatially resolved properties of the interstellar medium (ISM) at scales of 1–5 kpc (0farcs1–0farcs6). The velocity fields of our sources, traced by the 12CO(J = 3–2) emission, are consistent with disk rotation to the first order, implying average dynamical masses of ~3 × 1011 ${M}_{\odot }$ within two half-light radii. Through a Bayesian approach we investigate the uncertainties inherent to dynamically constraining total gas masses. We explore the covariance between the stellar mass-to-light ratio and CO-to-H2 conversion factor, α CO, finding values of ${\alpha }_{\mathrm{CO}}={1.1}_{-0.7}^{+0.8}$ for dark matter fractions of 15%. We show that the resolved spatial distribution of the gas and dust continuum can be uncorrelated to the stellar emission, challenging energy balance assumptions in global SED fitting. Through a stacking analysis of the resolved radial profiles of the CO(3–2), stellar, and dust continuum emission in SMG samples, we find that the cool molecular gas emission in these sources (radii ~5–14 kpc) is clearly more extended than the rest-frame ~250 μm dust continuum by a factor >2. We propose that assuming a constant dust-to-gas ratio, this apparent difference in sizes can be explained by temperature and optical depth gradients alone. Our results suggest that caution must be exercised when extrapolating morphological properties of dust continuum observations to conclusions about the molecular gas phase of the interstellar medium (ISM).

Citation

Rivera, G. C., Hodge, J., Smail, I., Swinbank, A., Weiss, A., Wardlow, J., …Werf, P. V. D. (2018). Resolving the ISM at the Peak of Cosmic Star Formation with ALMA: The Distribution of CO and Dust Continuum in z ∼ 2.5 Submillimeter Galaxies. Astrophysical Journal, 863(1), Article 56. https://doi.org/10.3847/1538-4357/aacffa

Journal Article Type	Article
Acceptance Date	Jun 25, 2018
Online Publication Date	Aug 9, 2018
Publication Date	Aug 9, 2018
Deposit Date	Aug 23, 2018
Publicly Available Date	Aug 23, 2018
Journal	Astrophysical Journal
Print ISSN	0004-637X
Publisher	American Astronomical Society
Peer Reviewed	Peer Reviewed
Volume	863
Issue	1
Article Number	56
DOI	https://doi.org/10.3847/1538-4357/aacffa