4 research outputs found
A Hubble Space Telescope NICMOS and ACS morphological study of z similar to 2 submillimetre galaxies
We present a quantitative morphological analysis using Hubble Space Telescope Near Infrared Camera and Multi-Object Spectrometer H160-band imaging and Advanced Camera for Surveys I775-band imaging of 25 spectroscopically confirmed submillimetre galaxies (SMGs) which have redshifts between Graphic (Graphic). Our analysis also employs a comparison sample of more typical star-forming galaxies at similar redshifts (such as Lyman-break Galaxies) which have lower far-infrared luminosities. This is the first large-scale study of the morphologies of SMGs in the near-infrared at ∼ 0.1 arcsec resolution (≲1 kpc). We find that the half-light radii of the SMGs (rh= 2.3 ± 0.3 and 2.8 ± 0.4 kpc in the observed I and H bands, respectively) and asymmetries are not statistically distinct from the comparison sample of star-forming galaxies. However, we demonstrate that the SMG morphologies differ more between the rest-frame UV and optical bands than typical star-forming galaxies and interpret this as evidence for structured dust obscuration. We show that the composite observed H-band light profile of SMGs is better fitted with a high Sersic index (n∼ 2) than with an exponential disc suggesting the stellar structure of SMGs is best described by a spheroid/elliptical galaxy light distribution. We also compare the sizes and stellar masses of SMGs to local and high-redshift populations and find that the SMGs have stellar densities which are comparable to (or slightly larger than) local early-type galaxies and comparable to luminous, red and dense galaxies at z∼ 1.5 which have been proposed as direct SMG descendants, although the SMG stellar masses and sizes are systematically larger. Overall, our results suggest that the physical processes occurring within the galaxies are too complex to be simply characterized by the rest-frame UV/optical morphologies which appear to be essentially decoupled from all other observables, such as bolometric luminosity, stellar or dynamical mass
The SCUBA-2 Cosmology Legacy Survey: The clustering of submillimetre galaxies in the UKIDSS UDS field
Submillimetre galaxies (SMGs) are among the most luminous dusty galaxies in the Universe, but their true nature remains unclear; are SMGs the progenitors of the massive elliptical galaxies we see in the local Universe, or are they just a short-lived phase among more typical star-forming galaxies? To explore this problem further, we investigate the clustering of SMGs identified in the SCUBA-2 Cosmology Legacy Survey. We use a catalogue of submillimetre (850 μm) source identifications derived using a combination of radio counterparts and colour/infrared selection to analyse a sample of 610 SMG counterparts in the United Kingdom Infrared Telescope (UKIRT) Infrared Deep Survey (UKIDSS) Ultra Deep Survey (UDS), making this the largest high-redshift sample of these galaxies to date. Using angular cross-correlation techniques, we estimate the halo masses for this large sample of SMGs and compare them with passive and star-forming galaxies selected in the same field. We find that SMGs, on average, occupy high-mass dark matter haloes (Mhalo > 1013 M⊙) at redshifts z > 2.5, consistent with being the progenitors of massive quiescent galaxies in present-day galaxy clusters. We also find evidence of downsizing, in which SMG activity shifts to lower mass haloes at lower redshifts. In terms of their clustering and halo masses, SMGs appear to be consistent with other star-forming galaxies at a given redshift
A direct calibration of thtae IRX-beta relation in Lyman-break Galaxies at z=3-5
We use a sample of 4209 Lyman-break galaxies (LBGs) at z 3, 4, and 5 in the UKIRT
Infrared Deep Sky Survey Ultra Deep Survey field to investigate the relationship between the
observed slope of the stellar continuum emission in the ultraviolet, β, and the thermal dust
emission, as quantified via the so-called ‘infrared excess’ (IRX ≡ LIR/LUV). Through a stacking
analysis, we directly measure the 850-μm flux density of LBGs in our deep (0.9 mJy) James
Clerk Maxwell Telescope SCUBA-2 850-μm map as well as deep public Herschel/SPIRE
250-, 350-, and 500-μm imaging. We establish functional forms for the IRX–β relation to
z ∼ 5, confirming that there is no significant redshift evolution of the relation, and that the
resulting average IRX–β curve is consistent with a Calzetti-like attenuation law. Comparing
our results with recent works in the literature, we confirm that discrepancies in the slope of
the IRX–β relation are driven by biases in the methodology used to determine the ultraviolet
slopes. Consistent results are found when IRX–β is evaluated by stacking in bins of stellar
mass, and we argue that the near-linear IRX–M relationship is a better proxy for correcting
observed ultraviolet luminosities to total star formation rates, provided an accurate handle on
M and also gives clues as to the physical driver of the role of dust-obscured star formation in
high-redshift galaxie
The SCUBA-2 Cosmology Legacy Survey: the clustering of submillimetre galaxies in the UKIDSS UDS field
Submillimetre galaxies (SMGs) are among the most luminous dusty galaxies in the Universe, but their true nature remains unclear; are SMGs the progenitors of the massive elliptical galaxies we see in the local Universe, or are they just a short-lived phase among more typical star-forming galaxies? To explore this problem further, we investigate the clustering of SMGs identified in the SCUBA-2 Cosmology Legacy Survey. We use a catalogue of submillimetre (850 μm) source identifications derived using a combination of radio counterparts and colour/infrared selection to analyse a sample of 610 SMG counterparts in the United Kingdom Infrared Telescope (UKIRT) Infrared Deep Survey (UKIDSS) Ultra Deep Survey (UDS), making this the largest high-redshift sample of these galaxies to date. Using angular cross-correlation techniques, we estimate the halo masses for this large sample of SMGs and compare them with passive and star-forming galaxies selected in the same field. We find that SMGs, on average, occupy high-mass dark matter haloes (Mhalo > 1013 M⊙) at redshifts z > 2.5, consistent with being the progenitors of massive quiescent galaxies in present-day galaxy clusters. We also find evidence of downsizing, in which SMG activity shifts to lower mass haloes at lower redshifts. In terms of their clustering and halo masses, SMGs appear to be consistent with other star-forming galaxies at a given redshift.ISSN:0035-8711ISSN:1365-296