A spatially resolved study of cold dust, molecular gas, HII regions, and stars in the $z=2.12$ submillimeter galaxy ALESS67.1

Abstract

We present detailed studies of a $z=2.12$ submillimeter galaxy, ALESS67.1, using sub-arcsecond resolution ALMA, AO-aided VLT/SINFONI, and HST/CANDELS data to investigate the kinematics and spatial distributions of dust emission (870 $\mu$m continuum), ${}^{12}$CO($J$=3-2), strong optical emission lines, and visible stars. Dynamical modelling 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 dataset allow 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, and UV and H$\alpha$ emission is significantly offset from the dust continuum. The spatial mismatch between UV continuum and the cold dust and gas reservoir supports the explanation that geometrical effects are responsible for the offset of dusty galaxy on the IRX-$\beta$ diagram. Using a dynamical method we derive an ${\alpha }_{\mathrm{CO}}=1.8\pm 1.0$, consistent with other SMGs that also have resolved CO and dust measurements. Assuming a single ${\alpha }_{\mathrm{CO}}$ value we also derive resolved gas and star-formation rate surface densities, and find that the core region of the galaxy ($\lesssim 5$ kpc) follows the trend of mergers on the Schmidt-Kennicutt relationship, whereas the outskirts ($\gtrsim 5$ 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.

16 pages, 8 figures, ApJ in press

References in corpus (34)

• Cosmic Star Formation History
• The 2.5 m Telescope of the Sloan Digital Sky Survey
• 3D-HST+CANDELS: The Evolution of the Galaxy Size-Mass Distribution since $z=3$
• UV Luminosity Functions at redshifts z~4 to z~10: 10000 Galaxies from HST Legacy Fields
• 3D-HST WFC3-selected Photometric Catalogs in the Five CANDELS/3D-HST Fields: Photometry, Photometric Redshifts and Stellar Masses
• The GALEX Ultraviolet Atlas of Nearby Galaxies
• An ALMA survey of Sub-millimeter Galaxies in the Extended Chandra Deep Field South: Physical properties derived from ultraviolet-to-radio modelling
• Kiloparsec-scale dust disks in high-redshift luminous submillimeter galaxies
• Strongly baryon-dominated disk galaxies at the peak of galaxy formation ten billion years ago
• The Large APEX Bolometer Camera LABOCA
• An ALMA survey of submillimetre galaxies in the Extended Chandra Deep Field South: High resolution 870um source counts
• Kinemetry of SINS High-Redshift Star-Forming Galaxies: Distinguishing Rotating Disks from Major Mergers
• Dynamical Properties of z~2 Star Forming Galaxies and a Universal Star Formation Relation
• The SCUBA-2 Cosmology Legacy Survey: ALMA resolves the rest-frame far-infrared emission of sub-millimeter galaxies
• Submillimetre galaxies in a hierarchical universe: number counts, redshift distribution, and implications for the IMF
• Are Dusty Galaxies Blue? Insights on UV Attenuation from Dust-Selected Galaxies
• The kiloparsec-scale star formation law at redshift 4: wide-spread, highly efficient star formation in the dust-obscured starburst galaxy GN20
• An ALMA Survey of Submillimeter Galaxies in the Extended Chandra Deep Field South: Near-infrared morphologies and stellar sizes
• The Rest-Frame Submillimeter Spectrum of High-Redshift, Dusty, Star-Forming Galaxies
• An ALMA survey of submillimetre galaxies in the Extended Chandra Deep Field South: Spectroscopic redshifts
• The Physical Scale of the Far-Infrared Emission in the Most Luminous Submillimeter Galaxies
• ALMA Spectroscopic Survey in the Hubble Ultra Deep Field: Molecular gas reservoirs in high-redshift galaxies
• Cold Molecular Gas in Merger Remnants: I. Formation of Molecular Gas Disks
• The IRX-Beta Dust Attenuation Relation in Cosmological Galaxy Formation Simulations
• Dissecting the IRX - $\beta$ dust attenuation relation: exploring the physical origin of observed variations in galaxies
• Simulated observations of sub-millimetre galaxies: the impact of single-dish resolution and field variance
• Imaging Molecular Gas in the Luminous Merger NGC 3256 : Detection of High-Velocity Gas and Twin Gas Peaks in the Double Nucleus
• Lens Models of Herschel-Selected Galaxies From High-Resolution Near-IR Observations
• SINFONI-HiZELS: The dynamics, merger rates & metallicity gradients of `typical' star-forming galaxies at $z$ = 0.8-2.2
• Kinematic classifications of local interacting galaxies: implications for the merger/disk classifications at high-z
• Tracing cool molecular gas and star formation on $\sim 100$pc scales within a $z=2.3$ galaxy
• The AT-LESS CO(1-0) survey of submillimetre galaxies in the Extended Chandra Deep Field South: First results on cold molecular gas in galaxies at z ~ 2
• A resolved map of the infrared excess in a Lyman Break Galaxy at z=3
• Star Formation Rate and Extinction in Faint z~4 Lyman-Break Galaxies

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