The Dust and [C ii] Morphologies of Redshift ∼4.5 Sub-millimeter Galaxies at ∼200 pc Resolution: The Absence of Large Clumps in the Interstellar Medium at High-redshift

Abstract

Additional information: 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-pro t 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 deep, high-resolution (0 03, 200 pc) ALMA Band 7 observations covering the dust continuum and [C II] λ157.7 μm emission in four z∼4.4-4.8 sub-millimeter galaxies (SMGs) selected from the ALESS and AS2UDS surveys. The data show that the rest-frame 160 μm (observed 345 GHz) dust emission is consistent with smooth morphologies on kpc scales for three of the sources. One source, UDS 47.0, displays apparent substructure, but this is also consistent with a smooth morphology-as indicated by simulations showing that smooth exponential disks can appear clumpy when observed at the high angular resolution (0 03) and depth of these observations (s~-27 47 345 GHz μJy beam −1 ). The four SMGs are bright [C II] emitters. We extract [C II] spectra from the high-resolution data, and recover ∼20%-100% of the [C II] flux and ∼40%-80% of the dust continuum emission, compared to the previous lower-resolution observations. When tapered to 0 2 resolution, our maps recover ∼80%-100% of the continuum emission, indicating that ∼60% of the emission is resolved out on ∼200 pc scales. We find that the [C II] emission in high-redshift galaxies is more spatially extended than the rest-frame 160 μm dust continuum by a factor of 1.6±0.4. By considering the [ ] L C II /L FIR ratio as a function of the star formation rate surface density (S SFR ), we revisit the [C II] deficit and suggest that the decline in the [ ] L C II /L FIR ratio as a function of S SFR is consistent with local processes. We also explore the physical drivers that may be responsible for these trends and can give rise to the properties found in the densest regions of SMGs.

Full of Orions: a 200-pc mapping of the interstellar medium in the redshift-3 lensed dusty star-forming galaxy SDP.81

“…11), as well as the Herschel observations of ULIRGs from the GOALS sample (Díaz-Santos et al 2017). However, as the [C ii] emission is significantly more extended than the FIR continuum (in line with Gullberg et al 2018;Rybak et al 2019), the source-averaged [C ii/FIR measurement provides only an upper limit on the [C ii]/FIR ratio in the central, FIR-bright region. The large extent of the [C ii] emission compared to the FIR continuum implies that the spatiallyaveraged [C ii]/FIR measurements in high-redshift sourcesas inferred from unresolved observations -mask the potentially very strong [C ii]/FIR deficit in the actual star-forming regions.…”

A Noncorotating Gas Component in an Extreme Starburst at z = 4.3

“…The kinematic parameters agree well with those derived from the previous fitting of a 0.3 ′′resolution [C ii] cube with a channel width of 50 km s −1 (Tadaki et al 2019), implying that measurements of maximum rotation velocity and local velocity dispersion do not require very high-resolution observations even in compact SMGs. This is thanks to the fact that the [C ii] emission is relatively extended compared to the dust continuum and CO line emission (Gullberg et al 2018;Tadaki et al 2019). Given that [C ii] emission is completely resolved out in 0.…”

Using [C ii] 158 μm Emission from Isolated ISM Phases as a Star Formation Rate Indicator

“…As multiple studies have found the [CII] deficit to be a local effect (Smith et al 2017;Gullberg et al 2018), we use the extended SPIRE coverage to determine if there are significant differences between the behavior of the phase-separated [CII] deficit in the inner nuclear regions of these galaxies and the more extended disks. In order to test these differences, we divide the BtP regions into 'Inner' and 'Outer' regions, with Inner regions centered within 0.25R 25 and Outer regions as any falling outside of this limit.…”

“…An intriguing application of an improved [CII]-based SFR indicator lies in the realm of high redshift galaxies. There have been many detections of the [CII] 158 µm line in galaxies from z ∼ 1 to z ∼ 7 Ivison et al 2010;Stacey et al 2010;Graciá-Carpio et al 2011;Valtchanov et al 2011;Gullberg et al 2015;Malhotra et al 2017;Barisic et al 2017;Gullberg et al 2018;Rybak et al 2019). The brightness of the [CII] line enables detections across a wide range of distances, making it a popular tool for probing the PDR properties and kinematics of galaxies in the high-redshift Universe.…”