To appear in "Hunting for the Dark: The Hidden Side of Galaxy Formation", Malta, 19-23 Oct. 2009, eds. V.P. Debattista & C.C. Popescu, AIP Conf. Ser., in press
In this brief, partial, incomplete and egregiously self-citing review I will summarise some of the key results in the past few years in surveys for dusty star-forming galaxies and some exciting prospects for forthcoming surveys.
We report the serendipitous discovery of a dusty, starbursting galaxy at $z=5.667$ (hereafter called CRLE) in close physical association with the "normal" main-sequence galaxy HZ10 at $z=5.654$. CRLE was identified by detection of [CII], [NII] and CO(2-1) line emission, making it the highest redshift, most luminous starburst in the COSMOS field. This massive, dusty galaxy appears to be forming stars at a rate of at least 1500$\,M_\odot$ yr$^{-1}$ in a compact region only $\sim3$ kpc in diameter. The dynamical and dust emission properties of CRLE suggest an ongoing merger driving the starburst,…
We report the $4 \, σ$ detection of a faint object with a flux of ~ 0.3 mJy, in the vicinity of the quadruply lensed QSO MG0414+0534 using the Atacama Large Millimeter/submillimeter array (ALMA) Band 7. The object is most probably a dusty dark dwarf galaxy, which has not been detected in either the optical, near-infrared (NIR) or radio (cm) bands. An anomaly in the flux ratio of the lensed images observed in Band 7 and the mid-infrared (MIR) band and the reddening of the QSO light color can be simultaneously explained if we consider the object as a lensing substructure with an ellipticity ~ 0.…
We report Atacama Large Millimetre Array (ALMA) observations of four high-redshift dusty star-forming galaxy candidates selected from far-Infrared (FIR)/submm observations in the COSMOS field. We securely detect all galaxies in the continuum and spectroscopically confirm them at z=3.62--5.85 using ALMA 3mm line scans, detecting multiple CO and/or [CI] transitions. This includes the most distant dusty galaxy currently known in the COSMOS field, ID85001929 at z=5.847. These redshifts are lower than we had expected as these galaxies have substantially colder dust temperatures (i.e., their SEDs pe…
Our understanding of the redshift $z>3$ galaxy population relies largely on samples selected using the popular "dropout" technique, typically consisting of UV-bright galaxies with blue colors and prominent Lyman breaks. As it is currently unknown if these galaxies are representative of the massive galaxy population, we here use the FourStar Galaxy Evolution (ZFOURGE) Survey to create a stellar mass-limited sample at $z=3-4$. Uniquely, ZFOURGE uses deep near-infrared medium-bandwidth filters to derive accurate photometric redshifts and stellar population properties. The mass-complete sample con…
We present a study of six far-infrared fine structure lines in the z=4.225 lensed dusty star-forming galaxy SPT0418-47 to probe the physical conditions of its InterStellar Medium (ISM). In particular, we report Atacama Pathfinder EXperiment (APEX) detections of the [OI]145um and [OIII]88um lines and Atacama Compact Array (ACA) detections of the [NII]122 and 205um lines. The [OI]145um / [CII]158um line ratio is ~5x higher compared to the average of local galaxies. We interpret this as evidence that the ISM is dominated by photo-dissociation regions with high gas densities. The line ratios, and …
The gravitationally-lensed galaxy A1689-zD1 is one of the most distant spectroscopically confirmed sources ($z=7.5$). It is the earliest known galaxy where the interstellar medium (ISM) has been detected; dust emission was detected with the Atacama Large Millimetre Array (ALMA). A1689-zD1 is also unusual among high-redshift dust emitters as it is a sub-L* galaxy and is therefore a good prospect for the detection of gaseous ISM in a more typical galaxy at this redshift. We observed A1689-zD1 with ALMA in bands 6 and 7 and with the Green Bank Telescope (GBT) in band $Q$. To study the structure o…
We present ALMA observations on and around the radio-quiet quasar UM287 at $z=2.28$. Together with a companion quasar, UM287 is believed to play a major role in powering the surrounding enormous Ly$α$ nebula (ELAN), dubbed the Slug ELAN, that has an end-to-end size of 450 physical kpc. In addition to the quasars, we detect a new dusty star-forming galaxy (DSFG), dubbed the Slug-DSFG, in 2 mm continuum with a single emission line consistent with CO(4-3). The Slug-DSFG sits at a projected distance of 100 kpc south-east from UM287, with a systemic velocity difference of $-360\pm30$ km s$^{-1}$ wi…
We present strong empirical evidence for a physical connection between the occurrence of a starburst (SB) and a luminous AGN phase. Drawing infrared (IR), X-ray, and optically selected samples from COSMOS, we find that the locus of type-2 AGN hosts in the optical colour-magnitude (U-V/V) and colour-colour (U-V/V-J) space significantly overlaps with that of IR-luminous (L_IR > 10^10 L_sun) galaxies. Based on our observations, we propose that, when simultaneously building their black hole and stellar masses, type-2 AGN hosts are located in the same part of colour-colour space as dusty star-formi…
We report the discovery of an intrinsically faint, quintuply-imaged, dusty galaxy MACS0600-z6 at a redshift $z=$6.07 viewed through the cluster MACSJ0600.1-2008 ($z$=0.46). A $\simeq4σ$ dust detection is seen at 1.2mm as part of the ALMA Lensing Cluster Survey (ALCS), an on-going ALMA Large program, and the redshift is secured via [C II] 158 $μ$m emission described in a companion paper. In addition, spectroscopic follow-up with GMOS/Gemini-North shows a break in the galaxy's spectrum, consistent with the Lyman break at that redshift. We use a detailed mass model of the cluster and infer a magn…
Galaxy clusters are the most massive collapsed structures in the universe whose potential wells are filled with hot, X-ray emitting intracluster medium. Observations however show that a significant number of clusters (the so-called cool-core clusters) also contain large amounts of cold gas in their centres, some of which is in the form of spatially extended filaments spanning scales of tens of kiloparsecs. These findings have raised questions about the origin of the cold gas, as well as its relationship with the central active galactic nucleus (AGN), whose feedback has been established as a ub…
We report interferometric imaging of [CII] and OH emission toward the center of the galaxy protocluster associated with the z=5.3 submillimeter galaxy (SMG) AzTEC-3, using the Atacama Large (sub)Millimeter Array (ALMA). We detect strong [CII], OH, and rest-frame 157.7 um continuum emission toward the SMG. The [CII] emission is distributed over a scale of 3.9 kpc, implying a dynamical mass of 9.7 x 10^10 Msun, and a star formation rate (SFR) surface density of Sigma_SFR = 530 Msun/yr/kpc2. This suggests that AzTEC-3 forms stars at Sigma_SFR approaching the Eddington limit for radiation pressure…
We exploit the continuity equation approach and the `main sequence' star-formation timescales to show that the observed high abundance of galaxies with stellar masses > a few 10^10 M_sun at redshift z>4 implies the existence of a galaxy population featuring large star formation rates (SFRs) > 10^2 M_sun/yr in heavily dust-obscured conditions. These galaxies constitute the high-redshift counterparts of the dusty star-forming population already surveyed for z<3 in the far-IR band by the Herschel space observatory. We work out specific predictions for the evolution of the corresponding stellar ma…
We report the discovery of the host galaxy of dark burst GRB080607 at z_GRB=3.036. GRB080607 is a unique case of a highly extinguished (A_V~3 mag) afterglow that was yet sufficiently bright for high-quality absorption-line spectroscopy. The host galaxy is clearly resolved in deep HST WF3/IR F160W images and well detected in the Spitzer IRAC 3.5 micron and 4.5 micron channels, while displaying little/no fluxes in deep optical images from Keck and Magellan. The extremely red optical-infrared colors are consistent with the large extinction seen in the afterglow light, suggesting that the large am…
We report the clearest detection to date of dusty torus signatures in a Weak-Line Radio Galaxy (WLRG). The deep Spitzer InfraRed Spectrograph (IRS) rest-frame mid-infrared (MIR) spectrum of the WLRG PKS 0043-42 (z=0.116) shows a clear spectral turnover at wavelengths longer than ~20 micron suggestive of warm dust, as well as a 9.7 micron silicate absorption feature. In addition, the hard X-ray results, based on Chandra data, strongly support a picture in which PKS 0043-42 has a torus and accretion disc more typical of Strong-Line Radio Galaxies (SLRGs). The MIR and X-ray spectra are markedly d…
The active galactic nucleus (AGN) phenomena results from a supermassive black hole accreting its surrounding gaseous and dusty material. The infrared (IR) regime provides most of the information to characterize the dusty structures that bridge from the galaxy to the black hole, providing clues to the black hole growth and host galaxy evolution. Over the past several decades, with the commissioning of various ground, airborne and space IR observing facilities, our interpretations of the AGN circumnuclear structures have advanced significantly through improved understanding of how their dust emi…
We present observations of SPT-S J053816-5030.8, a gravitationally-lensed dusty star forming galaxy (DSFG) at z = 2.7817, first discovered at millimeter wavelengths by the South Pole Telescope. SPT 0538-50 is typical of the brightest sources found by wide-field millimeter-wavelength surveys, being lensed by an intervening galaxy at moderate redshift (in this instance, at z = 0.441). We present a wide array of multi-wavelength spectroscopic and photometric data on SPT 0538-50, including data from ALMA, Herschel PACS and SPIRE, Hubble, Spitzer, VLT, ATCA, APEX, and the SMA. We use high resolutio…
We present U, V, and I-band images of the host galaxy of Hercules A (3C 348) obtained with HST/WFC3/UVIS. We find a network of dusty filaments which are more complex and extended than seen in earlier HST observations. The filaments are associated with a faint blue continuum light (possibly from young stars) and faint H-alpha emission. It seems likely that the cold gas and dust has been stripped from a companion galaxy now seen as a secondary nucleus. There are dusty filaments aligned with the base of the jets on both eastern and western sides of the galaxy. The morphology of the filaments is d…
To trace how dust-obscured star formation varies with environment, we compare the fraction of 24 micron sources in a super galaxy group to the field and a rich galaxy cluster at z~0.35. We draw on multi-wavelength observations that combine Hubble, Chandra, and Spitzer imaging with extensive optical spectroscopy (>1800 redshifts) to isolate galaxies in each environment and thus ensure a uniform analysis. We focus on the four galaxy groups in supergroup 1120-12 that will merge to form a galaxy cluster comparable in mass to Coma. We find that 1) the fraction of supergroup galaxies with SFR(IR)>3 …
In the course of our 870um APEX/LABOCA follow up of the Herschel Lensing Survey we have detected a source in AS1063 (RXC J2248.7-4431), that has no counterparts in any of the Herschel PACS/SPIRE bands, it is a Herschel 'drop-out' with S_870/S_500>0.5. The 870um emission is extended and centered on the brightest cluster galaxy suggesting either a multiply imaged background source or substructure in the Sunyaev-Zel'dovich (SZ) increment due to inhomogeneities in the hot cluster gas of this merging cluster. We discuss both interpretations with emphasis on the putative lensed source. Based on the …
We present an IR study of high-redshift galaxy clusters with the MIPS camera on the Spitzer Space Telescope. Employing a sample of 42 clusters from the RCS-1 over the redshift range 0.3 < z < 1.0 and spanning an approximate range in mass of 10^{14-15} Msun, we show the number of IR-luminous galaxies in clusters above a fixed IR luminosity of 2x10^{11} Msun per unit cluster mass evolves as (1+z)^{5.1+/-1.9}. These results assume a single star forming galaxy template; the presence of AGN, and an evolution in their relative contribution to the mid-IR galaxy emission, will alter the overall number…
Warm gas and dust surround the innermost regions of active galactic nuclei (AGN). They provide the material for accretion onto the super-massive black hole and they are held responsible for the orientation-dependent obscuration of the central engine. The AGN-heated dust distributions turn out to be very compact with sizes on scales of about a parsec in the mid-infrared. Only infrared interferometry currently provides the necessary angular resolution to directly study the physical properties of this dust. Size estimates for the dust distributions derived from interferometric observations can be…
We report 345 GHz continuum observations of the host galaxies of gamma-ray bursts (GRBs) 021004 and 080607 at z>2 using the Atacama Large Millimeter/Submillimeter Array (ALMA) in Cycle 0. Of the two bursts, GRB021004 is one of the few GRBs that originates in a Lyman limit host, while GRB080607 is classified as a "dark burst" and its host galaxy is a candidate of dusty star forming galaxy at z~3. With an order of magnitude improvement in the sensitivities of the new imaging searches, we detect the host galaxy of GRB080607 with a flux of S_{345} = 0.31+/-0.09 mJy and a corresponding infrared lum…
We present FitSKIRT, a method to efficiently fit radiative transfer models to UV/optical images of dusty galaxies. These images have the advantage that they have better spatial resolution compared to FIR/submm data. FitSKIRT uses the GAlib genetic algorithm library to optimize the output of the SKIRT Monte Carlo radiative transfer code. Genetic algorithms prove to be a valuable tool in handling the multi- dimensional search space as well as the noise induced by the random nature of the Monte Carlo radiative transfer code. FitSKIRT is tested on artificial images of a simulated edge-on spiral ga…
[Abridged]. Here, we report on the discovery of the galaxy counterpart of the z_abs=2.58 DLA on the line-of-sight to the z=3.07 quasar SDSS J091826.16+163609.0. The galaxy counterpart of the DLA is detected in the OIII 5007 and OII 3726,3729 emission lines redshifted into the NIR at an impact parameter of 16 kpc. Ly-alpha emission is not detected. The upper limit implies that Ly-alpha emission from this galaxy is suppressed by more than an order of magnitude. The DLA is amongst the most metal-rich DLAs studied so far at comparable redshifts. We find evidence for substantial depletion of refrac…
We study the abundance of substructure in the matter density near galaxies using ALMA Science Verification observations of the strong lensing system SDP.81. We present a method to measure the abundance of subhalos around galaxies using interferometric observations of gravitational lenses. Using simulated ALMA observations, we explore the effects of various systematics, including antenna phase errors and source priors, and show how such errors may be measured or marginalized. We apply our formalism to ALMA observations of SDP.81. We find evidence for the presence of a $M=10^{8.96\pm 0.12} M_{\o…
Studying the average properties of active galactic nuclei (AGN) host stellar populations is an important step in understanding the role of AGN in galaxy evolution and the processes which trigger and fuel AGN activity. Here we calculate model spectral energy distributions (SEDs) that include emission from the AGN, the host galaxy stellar population, and dust enshrouded star formation. Using the framework of cosmic X-ray background population synthesis modeling, the model AGN hosts are constrained using optical (B band) and near infrared (J band, 3.6 um, 5.7 um, 8.0 um, and 24 um) luminosity fun…
We exploit the deepest existing far-infrared (FIR) data obtained so far by Herschel at 100 and 160 um in the GOODS-N, as part of the PACS Evolutionary Probe (PEP) survey, to derive for the first time the evolution of the rest-frame 60-um, 90-um, and total IR luminosity functions (LFs) of galaxies and AGNs from z=0 to unprecedented high redshifts (z~2-3). The PEP LFs were computed using the 1/Vmax method. The FIR sources were classified by means of a detailed broad- band SED-fitting analysis and spectral characterisation. Based on the best-fit model results, k-correction and total IR (8-1000 um…