THE SPACE DENSITY OF LUMINOUS DUSTY STAR-FORMING GALAXIES AT z > 4: SCUBA-2 AND LABOCA IMAGING OF ULTRARED GALAXIES FROM HERSCHEL-ATLAS

Abstract

Citation for published item:svisonD FtF nd vewisD eFtFF nd eissD eF nd erumugmD F nd impsonD tFwF nd rollndD FF nd wddoxD F nd hunneD vF nd linteD iF nd vn der erfD F nd ymontD eF nd hnneruerD rF nd milD sF nd fertoldiD pF nd fremerD wF nd fussmnnD FF nd giD FEF nd glementsD hFvF nd gooryD eF nd he ottiD qF nd ilesD FeF nd pullerD gF nd qonzlezExuevoD tF nd srD iF nd xegrelloD wF nd yteoD sF nd ¡ erezEpournonD sF nd iehersD hF nd tevensD tFeF nd winnkD eFwF nd rdlowD tF @PHITA 9he spe density of luminous dusty strEforming glxies t z b R X gfeEP nd vefyge imging of ultrred glxies from rershelEeveF9D estrophysil journlFD VQP @IAF pF UVF Further information on publisher's website: 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-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. ABSTRACT Until recently, only a handful of dusty, star-forming galaxies (DSFGs) were known at z>4, most of them significantly amplified by gravitational lensing. Here, we have increased the number of such DSFGs substantially, selecting galaxies from the uniquely wide 250, 350, and 500 μm Herschel-ATLAS imaging survey on the basis of their extremely red far-infrared colors and faint 350 and 500 μm flux densities, based on which, they are expected to be largely unlensed, luminous, rare, and very distant. The addition of ground-based continuum photometry at longer wavelengths from the James Clerk Maxwell Telescope and the Atacama Pathfinder Experiment allows us to identify the dust peak in their spectral energy distributions (SEDs), with which we can better constrain their redshifts. We select the SED templates that are best able to determine photometric redshifts using a sample of 69 high-redshift, lensed DSFGs, then perform checks to assess the impact of the CMB on our technique, and to quantify the systematic uncertainty associated with our photometric redshifts, σ=0.14 (1 + z), using a sample of 25 galaxies with spectroscopic redshifts, each consistent with our color selection. For Herschel-selected ultrared galaxies with typical colors of S 500 /S 250 ∼2.2 and S 500 /S 350 ∼1.3 and flux densities, S 500 ∼50 mJy, we determine a median redshift, = z 3.66 phot , an interquartile redshift range, 3.30-4.27, with a median rest-frame 8-1000 μm luminosity, L IR , of 1.3× 1013 L e . A third of the galaxies lie at z>4, suggesting a space density, ρ z>4 , of ≈6×10 −7 Mpc −3 . Our sample contains the most luminous known star-forming galaxies, and the most overdense cluster of starbursting proto-ellipticals found to date.

The Herschel Bright Sources (HerBS): sample definition and SCUBA-2 observations

“…The estimated redshifts and bolometric luminosities are listed in Table A1, as well as the photometric redshift estimates using the method from Ivison et al (2016). Figure 8 shows the distribution of sources as a function of redshift and luminosity.…”

“…The three distributions are very similar. We compare the redshift estimates against the method used in Ivison et al (2016). They fit three different templates (ALESS (Swinbank et al 2014), Cosmic Eyelash (Ivison, R. J. et al 2010;Swinbank et al 2010), and the template from Pope et al (2008)) to the flux measurements, and use the redshift estimate from the spectrum with lowest χ 2 -value.…”

“…The blue dots in each panel show the points for the specified template, while the smaller grey dots show the points for the other two templates. The bottom panel shows (z spec − z phot )/(1 + z spec ) for the three templates used for the redshift estimation in Ivison et al (2016), where the blue dots correspond to the template fit with the lowest χ 2 for each source individually, and the smaller grey dots are the values of the two remaining templates.…”

“…Similarly, Figure 6 shows a similar pattern of redshift errors for all three templates. The redshift estimation by Ivison et al (2016) might provide a slightly better estimation of the redshift, which are therefore added to the catalogue Table A1. The explanation for this lack of improvement is almost certainly the diversity of the population; the limit on the accuracy of photometric redshift estimates is not set by the accuracy of the average template but by the fact that galaxies have different spectral energy distributions.…”

“…The sample from Ivison et al (2016) is also from the H-ATLAS fields, and contains sources with a color-cut at S 500µm /S 250µm > 1.5 and S 500µm /S 350µm > 0.85, in order to select sources at high redshift. The sources were also selected to have relatively low 500 µm flux density of around 50 mJy, in order to select unlensed sources.…”