A Spatially Resolved Study of Cold Dust, Molecular Gas, H ii Regions, and Stars in the z = 2.12 Submillimeter Galaxy ALESS67.1

Abstract

van der (2017) 'A spatially resolved study of cold dust, molecular gas, H II regions, and stars in the z = 2.12 submillimeter galaxy ALESS67.1.', The astrophysical journal., 846 (2). p. 108.Further information on publisher's website:https://doi.org/10.3847/1538-4357/aa863aPublisher's copyright statement: c 2017. The American Astronomical Society. All rights reserved. Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. AbstractWe present detailed studies of a z=2.12 submillimeter galaxy, ALESS67.1, using sub-arcsecond resolution ALMA, adaptive optics-aided VLT/SINFONI, and Hubble Space Telescope (HST)/CANDELS data to investigate the kinematics and spatial distributions of dust emission (870 μm continuum), 12 CO(J=3-2), strong optical emission lines, and visible stars. Dynamical modeling of the optical emission lines suggests that ALESS67.1 is not a pure rotating disk but a merger, consistent with the apparent tidal features revealed in the HST imaging. Our sub-arcsecond resolution data set allows us to measure half-light radii for all the tracers, and we find a factor of 4-6 smaller sizes in dust continuum compared to all the other tracers, including 12 CO; also, ultraviolet (UV) and Hα emission are significantly offset from the dust continuum. The spatial mismatch between the UV continuum and the cold dust and gas reservoir supports the explanation that geometrical effects are responsible for the offset of the dusty galaxy on the IRX-β diagram. Using a dynamical method we derive an 1.8 1.0 CO a =  , consistent with other submillimeter galaxies (SMGs) that also have resolved CO and dust measurements. Assuming a single CO a value we also derive resolved gas and star formation rate surface densities, and find that the core region of the galaxy ( 5  kpc) follows the trend of mergers on the Schmidt-Kennicutt relationship, whereas the outskirts ( 5  kpc) lie on the locus of normal star-forming galaxies, suggesting different star formation efficiencies within one galaxy. Our results caution against using single size or morphology for different tracers of the star formation activity and gas content of galaxies, and therefore argue the need to use spatially resolved, multi-wavelength observations to interpret the properties of SMGs, and perhaps even for z 1 > galaxies in general.

Starburst to Quiescent from HST/ALMA: Stars and Dust Unveil Minor Mergers in Submillimeter Galaxies at z ∼ 4.5

“…This provides morphological and geometrical evidence for the origin of the DSFG offsets from the M99 relation (see also Chen et al 2017) being consistent with the extreme extinction expected from the compact and intense dust emission for this sample (see Section 4.3), implying that UV emission should be expected not to escape the starbursts.…”

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

“…While high-resolution studies of the dust continuum emission in SMGs with ALMA have shown that this material appears to be mostly distributed in compact regions (Ikarashi et al 2015;Simpson et al 2015;Hodge et al 2016;Tadaki et al 2017a), the extended sizes revealed by the few resolved CO detections of luminous sources (Riechers et al 2010;Hodge et al 2012;Emonts et al 2016;Chen et al 2017;Dannerbauer et al 2017;Ginolfi et al 2017;Tadaki et al 2017b) challenge the general assumptions of co-spatial interwoven dust and gas generally assumed by other models. Spatially resolved observations of CO and dust continuum emission for homogeneously selected samples and modeling of their interplay, e.g., through radiative transfer approximations, may help to characterize the distributions and physics of dust and gas in the high-redshift ISM.…”

“…Due to the high spatial resolution of the data, it is not trivial to estimate the masks on which to apply the CLEAN task. We adopted an iterative cleaning technique (e.g., Chen et al 2017), in order to optimize the mask size estimation to include possible extended low surface brightness emission. Iterative cleaning consists of drawing concentric circular mask regions at increasing radii and applying the CLEAN task and line flux extraction within them.…”

“…Only a handful of studies have characterized the ISM on subgalactic scales in unlensed high-redshift galaxies (e.g., Tacconi et al 2008;Engel et al 2010;Hodge et al 2012Hodge et al , 2013aAravena et al 2014;Decarli et al 2016;Chen et al 2017;Tadaki et al 2017b), and even fewer have studied the dust continuum emission and gas observations on comparable scales. High-resolution imaging is crucial for characterizing the ISM in galaxies, since apart from providing a better morphological description of the gas or dust continuum emission, this information is key for estimating fundamental properties such as gas surface density.…”

The CO Luminosity Density at High-z (COLDz) Survey: A Sensitive, Large-area Blind Search for Low-J CO Emission from Cold Gas in the Early Universe with the Karl G. Jansky Very Large Array

“…23 Another caveat to using FIR continuum emission instead of CO comes from the finding that the dust emission measured by ALMA may not always trace the bulk of the gas distribution. This is made clear by the small sizes of the dust-emitting regions compared to the star-forming regions and the gas as traced by CO emission (e.g., Ivison et al 2011;Riechers et al 2011bRiechers et al , 2014Simpson et al 2015;Hodge et al 2016;Chen et al 2017;Miettinen et al 2017).…”