VLA AND ALMA IMAGING OF INTENSE GALAXY-WIDE STAR FORMATION IN z ∼ 2 GALAXIES

Abstract

The 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 ;0 4 resolution extinction-independent distributions of star formation and dust in 11 star-forming galaxies (SFGs) at z=1.3-3.0. These galaxies are selected from sensitive blank-field surveys of the 2′×2′ Hubble Ultra-Deep Field at λ=5 cm and 1.3 mm using the Karl G. Jansky Very Large Array and Atacama Large Millimeter/submillimeter Array. They have star formation rates (SFRs), stellar masses, and dust properties representative of massive main-sequence SFGs at z∼2. Morphological classification performed on spatially resolved stellar mass maps indicates a mixture of disk and morphologically disturbed systems; half of the sample harbor X-ray active galactic nuclei (AGNs), thereby representing a diversity of z∼2 SFGs undergoing vigorous mass assembly. We find that their intense star formation most frequently occurs at the location of stellar-mass concentration and extends over an area comparable to their stellar-mass distribution, with a median diameter of 4.2±1.8 kpc. This provides direct evidence of galaxy-wide star formation in distant blank-field-selected mainsequence SFGs. The typical galactic-average SFR surface density is 2.5 M e yr −1 kpc −2 , sufficiently high to drive outflows. In X-ray-selected AGN where radio emission is enhanced over the level associated with star formation, the radio excess pinpoints the AGNs, which are found to be cospatial with star formation. The median extinctionindependent size of main-sequence SFGs is two times larger than those of bright submillimeter galaxies, whose SFRs are 3-8 times larger, providing a constraint on the characteristic SFR (∼300 M e yr −1 ) above which a significant population of more compact SFGs appears to emerge.

The ALMA Redshift 4 Survey (AR4S)

“…Rujopakarn et al (2016) confirmed this offset using the JVLA and 2MASS, measuring ∆δ = +0.26 ± 0.13 , and suggesting an issue in the absolute astrometry of the HST images. None of our targets falls in the HUDF, so we cannot directly double check their result.…”

The Compact, ∼1 kpc Host Galaxy of a Quasar at a Redshift of 7.1

“…This difference could be due to a systematic difference in the absolute astrometric calibration between UKIDSS and ALMA. It is not possible to verify this, as there are no other sources in the field within the ALMA field-of-view beam, but similar offsets between ALMA and optical/near-infrared images have been reported (e.g., in the Hubble Ultra Deep Field; see Aravena et al 2016;Rujopakarn et al 2016). No offset from the UKIDSS position was seen in the PdBI data (Venemans et al 2012).…”

A Subarcsecond Near-infrared View of Massive Galaxies at z > 1 with Gemini Multi-conjugate Adaptive Optics

“…The Herschel systems studied in this paper can also be compared to the high-resolution studies of z∼4 star-forming galaxies by Wiklind et al (2014), Hodge et al (2016), and Rujopakarn et al (2016) with HST and radio/submillimeter imaging with the VLA and ALMA, which reveal similar trends, namely disturbed host galaxy morphologies and starforming regions offset from the centroid of the stellar light (XMMC2_30 is a very good example). The fact that these morphologies persist into the K band (rest-frame optical) in the sample studied in this paper suggest that the appearance of these objects is not dominated by clumpy extinction, but instead reflects the actual distribution of stellar light.…”

“…Furthermore, by combining near-infrared imaging of the stellar light with high-resolution radio continuum imaging (which pinpoints the regions of star formation or nuclear activity in these systems) we can build up a much more complete picture of the nature of the galaxies. This is particularly valuable in dusty star-forming systems, where the peak of star formation activity may be offset from the peak of the visible stellar light (Rujopakarn et al 2016(Rujopakarn et al , 2018.…”

“…These observations have sufficient sensitivity to resolve emission on subarcsecond scales (e.g., Murphy et al 2017). In cases where a radio excess above the maximum level expected from star formation is identified, these observations can distinguish emission due to star formation from that due to AGNs (e.g., Rujopakarn et al 2016).…”