Search

We present a method for selecting z > 4 dusty, star-forming galaxies (DSFGs) using Herschel/Spectral and Photometric Imaging Receiver 250/350/500 μm flux densities to search for red sources. We apply this method to 21 deg2 of data from the HerMES survey to produce a catalog of 38 high-z candidates. Follow-up of the first five of these sources confirms that this method is efficient at selecting high-z DSFGs, with 4/5 at z = 4.3-6.3 (and the remaining source at z = 3.4), and that they are some of the most luminous dusty sources known. Comparison with previous DSFG samples, mostly selected at longer wavelengths (e.g., 850 μm) and in single-band surveys, shows that our method is much more efficient at selecting high-z DSFGs, in the sense that a much larger fraction are at z > 3. Correcting for the selection completeness and purity, we find that the number of bright (S 500 μm ≥ 30 mJy), red Herschel sources is 3.3 ± 0.8 deg-2. This is much higher than the number predicted by current models, suggesting that the DSFG population extends to higher redshifts than previously believed. If the shape of the luminosity function for high-z DSFGs is similar to that at z ∼ 2, rest-frame UV based studies may be missing a significant component of the star formation density at z = 4-6, even after correction for extinction. © 2014. The American Astronomical Society. All rights reserved.

Strong gravitational lenses are now being routinely discovered in wide-field surveys at (sub-)millimeter wavelengths. We present Submillimeter Array (SMA) high-spatial resolution imaging and Gemini-South and Multiple Mirror Telescope optical spectroscopy of strong lens candidates discovered in the two widest extragalactic surveys conducted by the Herschel Space Observatory: the Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS) and the Herschel Multi-tiered Extragalactic Survey (HerMES). From a sample of 30 Herschel sources with S 500 > 100 mJy, 21 are strongly lensed (i.e., multiply imaged), 4 are moderately lensed (i.e., singly imaged), and the remainder require additional data to determine their lensing status. We apply a visibility-plane lens modeling technique to the SMA data to recover information about the masses of the lenses as well as the intrinsic (i.e., unlensed) sizes (r half) and far-infrared luminosities (L FIR) of the lensed submillimeter galaxies (SMGs). The sample of lenses comprises primarily isolated massive galaxies, but includes some groups and clusters as well. Several of the lenses are located at z lens > 0.7, a redshift regime that is inaccessible to lens searches based on Sloan Digital Sky Survey spectroscopy. The lensed SMGs are amplified by factors that are significantly below statistical model predictions given the 500 μm flux densities of our sample. We speculate that this may reflect a deficiency in our understanding of the intrinsic sizes and luminosities of the brightest SMGs. The lensed SMGs span nearly one decade in L FIR (median L FIR = 7.9 × 10 12 L ) and two decades in FIR luminosity surface density (median ΣFIR = 6.0 × 1011 L kpc-2). The strong lenses in this sample and others identified via (sub-)mm surveys will provide a wealth of information regarding the astrophysics of galaxy formation and evolution over a wide range in redshift. © 2013. The American Astronomical Society. All rights reserved..

We present the results of a survey of CO(1−0) emission in 14 infrared luminous dusty star-forming galaxies (DSFGs) at 2 < z < 4 with the NSF's Karl G. Jansky Very Large Array. All sources are detected in 12CO(1−0), with an angular resolution of ∼1″. Seven sources show extended and complex structure. We measure CO luminosities of (μ) L CO (1 − 0) ′ = 0.4 – 2.9 × 10 11 K km s−1 pc2, and molecular gas masses of (μ) M H 2 = 1.3 – 8.6 × 10 11 M ⊙, where (μ) is the magnification factor. The derived molecular gas depletion times of t dep = 40–460 Myr, cover the expected range of both normal star-forming galaxies and starbursts. Compared to the higher − J CO transitions previously observed for the same sources, we find CO temperature brightness ratios of r 32/10 = 0.4–1.4, r 43/10 = 0.4–1.7, and r 54/10 = 0.3–1.3. We find a wide range of CO spectral line energy distributions (SLEDs), in agreement with other high- z DSFGs, with the exception of three sources that are most comparable to Cloverleaf and APM08279+5255. Based on radiative transfer modeling of the CO SLEDs we determine densities of n H 2 = 0.3 − 8.5 × 10 3 cm−3 and temperatures of T K = 100–200 K. Lastly, four sources are detected in the continuum, three have radio emission consistent with their infrared-derived star formation rates, while HerBS-70E requires an additional synchrotron radiation component from an active galactic nucleus. Overall, we find that even though the sample is similarly luminous in the infrared, by tracing the CO(1−0) emission a diversity of galaxy and excitation properties are revealed, demonstrating the importance of CO(1−0) observations in combination to higher- J transitions. [ABSTRACT FROM AUTHOR]

We report an ultrabright lensed submillimeter galaxy at zspec = 1.4796, identified as a result of a full-sky cross-correlation of the AllWISE and Planck compact source catalogs aimed at searching for bright submillimeter galaxies at z ∼ 1.5–2.8. Atacama Pathfinder Experiment (APEX)/LABOCA observations of the candidate galaxy reveal a source with flux S870μm = 54 ± 8 mJy. The position of the APEX source coincides with the position of the AllWISE mid-IR source and with the Einstein ring GAL-CLUS-022058s, observed with the Hubble Space Telescope. Archival VLT/FORS observations reveal the redshift of this Einstein ring, zspec = 1.4796, and the detection of the CO(5–4) line at zspec = 1.4802 with APEX/nFLASH230 confirms the redshift of the submillimeter emission. The lensed source appears to be gravitationally magnified by a massive foreground galaxy cluster lens at z = 0.36. We use Lenstool to model the gravitational lensing, which is close to a "fold arc" configuration for an elliptical mass distribution of the central halo, where four images of the lensed galaxy are seen; the mean magnification is μL = 18 ± 4. We have determined an intrinsic rest-frame infrared luminosity of LIR ≈1012L⊙ and a likely star formation rate of ∼70–170 M⊙yr−1. The molecular gas mass is Mmol ∼ 2.6 × 1010M⊙ and the gas fraction is f = 0.34 ± 0.07. We also obtain a stellar mass log (M*/M⊙) = 10.7 ± 0.1 and a specific star formation rate log (sSFR/Gyr−1) = 0.15 ± 0.03. This galaxy lies on the so-called main sequence of star-forming galaxies at this redshift. [ABSTRACT FROM AUTHOR]

We present Atacama Large Millimeter/submillimeter Array (ALMA) 2 mm continuum observations of a complete and unbiased sample of 99 870 μm selected submillimeter galaxies (SMGs) in the Extended Chandra Deep Field South (ALESS). Our observations of each SMG reach average sensitivities of 53 μJy beam−1. We measure the flux densities for 70 sources, for which we obtain a typical 870 μm-to-2 mm flux ratio of 14 ± 5. We do not find a redshift dependence of this flux ratio, which would be expected if the dust emission properties of our SMGs were the same at all redshifts. By combining our ALMA measurements with existing Herschel/SPIRE observations, we construct a (biased) subset of 27 galaxies for which the cool dust emission is sufficiently well sampled to obtain precise constraints on their dust properties using simple isothermal models. Thanks to our new 2 mm observations, the dust emissivity index is well constrained and robust against different dust opacity assumptions. The median dust emissivity index of our SMGs is β ≃ 1.9 ± 0.4, consistent with the emissivity index of dust in the Milky Way and other local and high-redshift galaxies, as well as classical dust-grain model predictions. We also find a negative correlation between the dust temperature and β, similar to low-redshift observational and theoretical studies. Our results indicate that β ≃ 2 in high-redshift dusty star-forming galaxies, implying little evolution in dust-grain properties between our SMGs and local dusty galaxy samples, and suggesting that these high-mass and high-metallicity galaxies have dust reservoirs driven by grain growth in their interstellar medium. [ABSTRACT FROM AUTHOR]

Dusty star-forming galaxies at high redshift (1 < z < 3) represent the most intense star-forming regions in the universe. Key aspects to these processes are the gas heating and cooling mechanisms, and although it is well known that these galaxies are gas-rich, little is known about the gas excitation conditions. Only a few detailed radiative transfer studies have been carried out owing to a lack of multiple line detections per galaxy. Here we examine these processes in a sample of 24 strongly lensed star-forming galaxies identified by the Planck satellite (LPs) at z ∼ 1.1–3.5. We analyze 162 CO rotational transitions (ranging from Jup = 1 to 12) and 37 atomic carbon fine-structure lines ([C i ]) in order to characterize the physical conditions of the gas in the sample of LPs. We simultaneously fit the CO and [C i ] lines and the dust continuum emission, using two different non-LTE, radiative transfer models. The first model represents a two-component gas density, while the second assumes a turbulence-driven lognormal gas density distribution. These LPs are among the most gas-rich, IR-luminous galaxies ever observed (μL L⊙; μLMISM = (2.7 ± 1.2) × 1012M⊙, with μL ∼ 10–30 the average lens magnification factor). Our results suggest that the turbulent interstellar medium present in the LPs can be well characterized by a high turbulent velocity dispersion (ΔVturb ∼ 100 km s−1) and ratios of gas kinetic temperature to dust temperature Tkin/Td ∼ 2.5, sustained on scales larger than a few kiloparsecs. We speculate that the average surface density of the molecular gas mass and IR luminosity, ∼ 103–4 M⊙ pc−2 and ∼ 1011–12 L⊙ kpc−2, arise from both stellar mechanical feedback and a steady momentum injection from the accretion of intergalactic gas. [ABSTRACT FROM AUTHOR]

We present spectral energy distributions (SEDs) of 69 QSOs at z > 5, covering a rest frame wavelength range of 0.1 μm to ∼80 μm, and centered on new Spitzer and Herschel observations. The detection rate of the QSOs with Spitzer is very high (97% at λrest ≲ 4 μm), but drops toward the Herschel bands with 30% detected in PACS (rest frame mid-infrared) and 15% additionally in the SPIRE (rest frame far-infrared; FIR). We perform multi-component SED fits for Herschel-detected objects and confirm that to match the observed SEDs, a clumpy torus model needs to be complemented by a hot (∼1300 K) component and, in cases with prominent FIR emission, also by a cold (∼50 K) component. In the FIR-detected cases the luminosity of the cold component is of the order of 1013L☼ which is likely heated by star formation. From the SED fits we also determine that the active galactic nucleus (AGN) dust-to-accretion disk luminosity ratio declines with UV/optical luminosity. Emission from hot (∼1300 K) dust is common in our sample, showing that nuclear dust is ubiquitous in luminous QSOs out to redshift 6. However, about 15% of the objects appear under-luminous in the near infrared compared to their optical emission and seem to be deficient in (but not devoid of) hot dust. Within our full sample, the QSOs detected with Herschel are found at the high luminosity end in LUV/opt and LNIR and show low equivalent widths (EWs) in Hα and in Lyα. In the distribution of Hα EWs, as determined from the Spitzer photometry, the high-redshift QSOs show little difference to low-redshift AGN. [ABSTRACT FROM AUTHOR]

We study the sub-millimeter properties of color-selected galaxies via a stacking analysis applied for the first time to interferometric data at sub-millimeter wavelengths. We base our study on 344 GHz ALMA continuum observations of ∼20″-wide fields centered on 86 sub-millimeter sources detected in the LABOCA Extended Chandra Deep Field South (ECDFS) Sub-millimeter Survey. We select various classes of galaxies (K-selected, star-forming sBzK galaxies, extremely red objects, and distant red galaxies) according to their optical/near-infrared fluxes. We find clear, >10σ detections in the stacked images of all these galaxy classes. We include in our stacking analysis Herschel/SPIRE data to constrain the dust spectral energy distribution of these galaxies. We find that their dust emission is well described by a modified blackbody with Tdust ≈ 30 K and β = 1.6 and infrared luminosities of (5-11) × 1011L☼ or implied star formation rates of 75-140 M☼ yr–1. We compare our results with those of previous studies based on single-dish observations at 870 μm and find that our flux densities are a factor 2-3 higher than previous estimates. The discrepancy is observed also after removing sources individually detected in ALESS maps. We report a similar discrepancy by repeating our analysis on 1.4 GHz observations of the whole ECDFS. Hence, we find tentative evidence that galaxies that are associated in projected and redshift space with sub-mm bright sources are brighter than the average population. Finally, we put our findings in the context of the cosmic star formation rate density as a function of redshift. [ABSTRACT FROM AUTHOR]

Strong gravitational lenses are now being routinely discovered in wide-field surveys at (sub-)millimeter wavelengths. We present Submillimeter Array (SMA) high-spatial resolution imaging and Gemini-South and Multiple Mirror Telescope optical spectroscopy of strong lens candidates discovered in the two widest extragalactic surveys conducted by the Herschel Space Observatory: the Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS) and the Herschel Multi-tiered Extragalactic Survey (HerMES). From a sample of 30 Herschel sources with S500 > 100 mJy, 21 are strongly lensed (i.e., multiply imaged), 4 are moderately lensed (i.e., singly imaged), and the remainder require additional data to determine their lensing status. We apply a visibility-plane lens modeling technique to the SMA data to recover information about the masses of the lenses as well as the intrinsic (i.e., unlensed) sizes (rhalf) and far-infrared luminosities (LFIR) of the lensed submillimeter galaxies (SMGs). The sample of lenses comprises primarily isolated massive galaxies, but includes some groups and clusters as well. Several of the lenses are located at zlens > 0.7, a redshift regime that is inaccessible to lens searches based on Sloan Digital Sky Survey spectroscopy. The lensed SMGs are amplified by factors that are significantly below statistical model predictions given the 500 μm flux densities of our sample. We speculate that this may reflect a deficiency in our understanding of the intrinsic sizes and luminosities of the brightest SMGs. The lensed SMGs span nearly one decade in LFIR (median LFIR = 7.9 × 1012L☼) and two decades in FIR luminosity surface density (median ΣFIR = 6.0 × 1011L☼ kpc–2). The strong lenses in this sample and others identified via (sub-)mm surveys will provide a wealth of information regarding the astrophysics of galaxy formation and evolution over a wide range in redshift. [ABSTRACT FROM AUTHOR]

The large gas and dust reservoirs of submillimeter galaxies (SMGs) could potentially provide ample fuel to trigger an active galactic nucleus (AGN), but previous studies of the AGN fraction in SMGs have been controversial largely due to the inhomogeneity and limited angular resolution of the available submillimeter surveys. Here we set improved constraints on the AGN fraction and X-ray properties of the SMGs with Atacama Large Millimeter/submillimeter Array (ALMA) and Chandra observations in the Extended Chandra Deep Field-South (E-CDF-S). This study is the first among similar works to have unambiguously identified the X-ray counterparts of SMGs; this is accomplished using the fully submillimeter-identified, statistically reliable SMG catalog with 99 SMGs from the ALMA LABOCA E-CDF-S Submillimeter Survey. We found 10 X-ray sources associated with SMGs (median redshift z = 2.3), of which eight were identified as AGNs using several techniques that enable cross-checking. The other two X-ray detected SMGs have levels of X-ray emission that can be plausibly explained by their star formation activity. Six of the eight SMG-AGNs are moderately/highly absorbed, with NH > 1023 cm–2. An analysis of the AGN fraction, taking into account the spatial variation of X-ray sensitivity, yields an AGN fraction of for AGNs with rest-frame 0.5-8 keV absorption-corrected luminosity ⩾7.8 × 1042 erg s–1; we provide estimated AGN fractions as a function of X-ray flux and luminosity. ALMA's high angular resolution also enables direct X-ray stacking at the precise positions of SMGs for the first time, and we found four potential SMG-AGNs in our stacking sample. [ABSTRACT FROM AUTHOR]

We present Herschel far-infrared (FIR) photometry of 11 quasars at redshiftz > 5 that have previously been detected at 1.2 mm. We perform full spectral energy distribution (SED) fits over the wavelength range λrest ~ 0.1-400 μm for those objects with good Herschel detections. These fits reveal the need for an additional FIR component besides the emission from a dusty active galactic nucleus (AGN)-powered torus. This additional FIR component has temperatures of TFIR ~ 40-60 K with luminosities of L8-1000 μm ~ 1013 L⊙ (accounting for 25%-60% of the bolometric FIR luminosity). If the FIR dust emission is due to star formation it would suggest star formation rates in excess of 1000 solar masses per year. We show that at long wavelengths (λrest ≳ 50 μm) the contribution of the AGN-powered torus emission is negligible. This explains how previous FIR studies of high-redshift quasars that relied on single-component fits to (ground-based) observations at λobs ≳ 350 μm reached TFIR and LFIR values similar to our complete SED fits. Stacking the Herschel data of four individually undetected sources reveals a significant average signal in the PACS bands but not in SPIRE. The average SED of sources with individual Herschel detections shows a striking surplus in near- and mid-infrared (MIR) emission when compared to common AGN templates. The comparison between two average SEDs (sources with and without individual Herschel detections) matched in the UV/optical indicates that for these objects the strength of the MIR emission may correlate with the strength of the FIR emission. [ABSTRACT FROM AUTHOR]

We present an Atacama Large Millimeter/submillimeter Array (ALMA) Cycle 0 survey of 126 submillimeter sources from the LABOCA ECDFS Submillimeter Survey (LESS). Our 870μm survey with ALMA (ALESS) has produced maps ~3× deeper and with a beam area ~200× smaller than the original LESS observations, doubling the current number of interferometrically-observed submillimeter sources. The high resolution of these maps allows us to resolve sources that were previously blended and accurately identify the origin of the submillimeter emission. We discuss the creation of the ALESS submillimeter galaxy (SMG) catalog, including the main sample of 99 SMGs and a supplementary sample of 32 SMGs. We find that at least 35% (possibly up to 50%) of the detected LABOCA sources have been resolved into multiple SMGs, and that the average number of SMGs per LESS source increases with LESS flux density. Using the (now precisely known) SMG positions, we empirically test the theoretical expectation for the uncertainty in the single-dish source positions. We also compare our catalog to the previously predicted radio/mid-infrared counterparts, finding that 45% of the ALESS SMGs were missed by this method. Our ~1."6 resolution allows us to measure a size of ~9 kpc × 5 kpc for the rest-frame ~300μm emission region in one resolved SMG, implying a star formation rate surface density of 80M☉ yr-1 kpc-2, and we constrain the emission regions in the remaining SMGs to be <10 kpc. As the first statistically reliable survey of SMGs, this will provide the basis for an unbiased multiwavelength study of SMG properties. [ABSTRACT FROM AUTHOR]

While the selection of strongly lensed galaxies (SLGs) with 500 µm flux density S500 > 100 mJy has proven to be rather straightforward, for many applications it is important to analyze samples larger than the ones obtained when confining ourselves to such a bright limit. Moreover, only by probing to fainter flux densities is it possible to exploit strong lensing to investigate the bulk of the high-z star-forming galaxy population.We describe HALOS (the Herschel-ATLAS Lensed Objects Selection), a method for efficiently selecting fainter candidate SLGs, reaching a surface density of ⋍1.5-2 deg-2, i.e., a factor of about 4-6 higher than that at the 100 mJy flux limit. HALOS will allow the selection of up to ~1000 candidate SLGs (with amplifications µ ≿ 2) over the full H-ATLAS survey area. Applying HALOS to the H-ATLAS Science Demonstration Phase field (⋍14.4deg²) we find 31 candidate SLGs, whose candidate lenses are identified in the VIKING near-infrared catalog. Using the available information on candidate sources and candidate lenses we tentatively estimate a ⋍72% purity of the sample. As expected, the purity decreases with decreasing flux density of the sources and with increasing angular separation between candidate sources and lenses. The redshift distribution of the candidate lensed sources is close to that reported for most previous surveys for lensed galaxies, while that of candidate lenses extends to redshifts substantially higher than found in the other surveys. The counts of candidate SLGs are also in good agreement with model predictions. Even though a key ingredient of the method is the deep near-infrared VIKING photometry, we show that H-ATLAS data alone allow the selection of a similarly deep sample of candidate SLGs with an efficiency close to 50%; a slightly lower surface density (⋍1.45 deg-2) can be reached with a ~70% efficiency. [ABSTRACT FROM AUTHOR]

We take advantage of the sensitivity and resolution of the Herschel Space Observatory, at 100 and 160 µm to directly image the thermal dust emission and investigate the infrared luminosities (LIR) and dust obscuration of typical star-forming (L*) galaxies at high redshift. Our sample consists of 146 UV-selected galaxies with spectroscopic redshifts 1.5 ≤ zspec < 2.6 in the GOODS-North field. Supplemented with deep Very Large Array and Spitzer imaging, we construct median stacks at the positions of these galaxies at 24, 100, and 160 µm, and 1.4 GHz. The comparison between these stacked fluxes and a variety of dust templates and calibrations implies that typical star-forming galaxies with UV luminosities LUV ≳ 1010 L⊙ at z ~ 2 are luminous infrared galaxies with a median LIR = (2.2 ± 0.3) x 1011 L⊙. Their median ratio of LIR to rest-frame 8 µm luminosity (L8) is LIR/L8 = 8.9 ± 1.3 and is ≈80% larger than that found for most star-forming galaxies at z ≲ 2. This apparent redshift evolution in the LIR/L8 ratio may be tied to the trend of larger infrared luminosity surface density for z ≳ 2 galaxies relative to those at lower redshift. Typical galaxies at 1.5 ≤ z < 2.6 have a median dust obscuration LIR/LUV = 7.1 ± 1.1, which corresponds to a dust correction factor, required to recover the bolometric star formation rate (SFR) from the unobscured UV SFR, of 5.2 ± 0.6. This result is similar to that inferred from previous investigations of the UV, Hα, 24 µm, radio, and X-ray properties of the same galaxies studied here. Stacking in bins of UV slope (β) implies that L* galaxies with redder spectral slopes are also dustier and that the correlation between β and dustiness is similar to that found for local starburst galaxies. Hence, the rest-frame ≃30 and 50 µm fluxes validate on average the use of the local UV attenuation curve to recover the dust attenuation of typical star-forming galaxies at high redshift. In the simplest interpretation, the agreement between the local and high-redshift UV attenuation curves suggests a similarity in the dust production and stellar and dust geometries of starburst galaxies over the last 10 billion years. [ABSTRACT FROM AUTHOR]

We report ground-based follow-up observations of the exceptional source, ID 141, one of the brightest sources detected so far in the Herschel Astrophysical Terahertz Large Area Survey cosmological survey. ID 141 was observed using the IRAM 30 m telescope and Plateau de Bure interferometer (PdBI), the Submillimeter Array, and the Atacama Pathfinder Experiment submillimeter telescope to measure the dust continuum and emission lines of the main isotope of carbon monoxide and carbon ([C I] and [C II]). The detection of strong CO emission lines with the PdBI confirms that ID 141 is at high redshift (ɀ = 4.243 ± 0.001). The strength of the continuum and emission lines suggests that ID 141 is gravitationally lensed. The width (ΔVFWHM ∼ 800 km s-1) and asymmetric profiles of the CO and carbon lines indicate orbital motion in a disk or a merger. The properties derived for ID 141 are compatible with an ultraluminous (LFIR ∼ (8.5 ± 0.3) x 1013 Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. Lʘ, where μL is the amplification factor), dense (n ≈ 104 cm-3), and warm (Tkin ≈ as 40 K) starburst galaxy, with an estimated star formation rate of (0.7-1.7) x 104 Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. Mʘ yr-1. The carbon emission lines indicate a dense (n ≈ 104 cm-3) photon-dominated region, illuminated by a far-UV radiation field a few thousand times more intense than that in our Galaxy. In conclusion, the physical properties of the high-ɀ galaxy ID 141 are remarkably similar to those of local ultraluminous infrared galaxies. [ABSTRACT FROM AUTHOR]

We analyze Hubble Space Telescope WFC3/H160-band observations of a sample of 48 Atacama Large Millimeter/submillimeter Array detected submillimeter galaxies (SMGs) in the Extended Chandra Deep Field South field, to study their stellar morphologies and sizes. We detect 79% ± 17% of the SMGs in the H160-band imaging with a median sensitivity of 27.8 mag, and most (80%) of the nondetections are SMGs with 870 μm fluxes of S870 < 3 mJy. With a surface brightness limit of μH ∼ 26 mag arcsec–2, we find that 82% ± 9% of the H160-band-detected SMGs at z = 1-3 appear to have disturbed morphologies, meaning they are visually classified as either irregulars or interacting systems, or both. By determining a Sérsic fit to the H160 surface brightness profiles, we derive a median Sérsic index of n = 1.2 ± 0.3 and a median half-light radius of re = 4.4 kpc for our SMGs at z = 1-3. We also find significant displacements between the positions of the H160 component and 870 μm emission in these systems, suggesting that the dusty starburst regions and less-obscured stellar distribution are not colocated. We find significant differences in the sizes and the Sérsic index between our z = 2-3 SMGs and z ∼ 2 quiescent galaxies, suggesting that a major transformation of the stellar light profile is needed in the quenching processes if SMGs are progenitors of the red-and-dead z ∼ 2 galaxies. Given the short-lived nature of SMGs, we postulate that the majority of the z = 2-3 SMGs with S870 ≳ 2 mJy are early/mid-stage major mergers. [ABSTRACT FROM AUTHOR]

We present Keck-Adaptive Optics and Hubble Space Telescope high resolution near-infrared (IR) imaging for 500 μm bright candidate lensing systems identified by the Herschel Multi-tiered Extragalactic Survey and Herschel Astrophysical Terahertz Large Area Survey. Out of 87 candidates with near-IR imaging, 15 (∼17%) display clear near-IR lensing morphologies. We present near-IR lens models to reconstruct and recover basic rest-frame optical morphological properties of the background galaxies from 12 new systems. Sources with the largest near-IR magnification factors also tend to be the most compact, consistent with the size bias predicted from simulations and previous lensing models for submillimeter galaxies (SMGs). For four new sources that also have high-resolution submillimeter maps, we test for differential lensing between the stellar and dust components and find that the 880 μm magnification factor (μ880) is ∼1.5 times higher than the near-IR magnification factor (μNIR), on average. We also find that the stellar emission is ∼2 times more extended in size than dust. The rest-frame optical properties of our sample of Herschel-selected lensed SMGs are consistent with those of unlensed SMGs, which suggests that the two populations are similar. [ABSTRACT FROM AUTHOR]

We present the first photometric redshift distribution for a large sample of 870 μm submillimeter galaxies (SMGs) with robust identifications based on observations with ALMA. In our analysis we consider 96 SMGs in the Extended Chandra Deep Field South, 77 of which have 4-19 band photometry. We model the SEDs for these 77 SMGs, deriving a median photometric redshift of zphot = 2.3 ± 0.1. The remaining 19 SMGs have insufficient photometry to derive photometric redshifts, but a stacking analysis of Herschel observations confirms they are not spurious. Assuming that these SMGs have an absolute H-band magnitude distribution comparable to that of a complete sample of z ∼ 1-2 SMGs, we demonstrate that they lie at slightly higher redshifts, raising the median redshift for SMGs to zphot = 2.5 ± 0.2. Critically we show that the proportion of galaxies undergoing an SMG-like phase at z ⩾ 3 is at most 35% ± 5% of the total population. We derive a median stellar mass of M⋆ = (8 ± 1) × 1010M☼, although there are systematic uncertainties of up to 5 × for individual sources. Assuming that the star formation activity in SMGs has a timescale of ∼100 Myr, we show that their descendants at z ∼ 0 would have a space density and MH distribution that are in good agreement with those of local ellipticals. In addition, the inferred mass-weighted ages of the local ellipticals broadly agree with the look-back times of the SMG events. Taken together, these results are consistent with a simple model that identifies SMGs as events that form most of the stars seen in the majority of luminous elliptical galaxies at the present day. [ABSTRACT FROM AUTHOR]

Using data from the mid-infrared to millimeter wavelengths for individual galaxies and for stacked ensembles at 0.5 < z < 2, we derive robust estimates of dust masses (Mdust) for main-sequence (MS) galaxies, which obey a tight correlation between star formation rate (SFR) and stellar mass (M*), and for starbursting galaxies that fall outside that relation. Exploiting the correlation of gas-to-dust mass with metallicity (Mgas/Mdust-Z), we use our measurements to constrain the gas content, CO-to-H2 conversion factors (αCO), and star formation efficiencies (SFE) of these distant galaxies. Using large statistical samples, we confirm that αCO and SFE are an order of magnitude higher and lower, respectively, in MS galaxies at high redshifts compared to the values of local galaxies with equivalently high infrared luminosities (LIR > 1012L☼). For galaxies within the MS, we show that the variations of specific star formation rates (sSFRs = SFR/M*) are driven by varying gas fractions. For relatively massive galaxies like those in our samples, we show that the hardness of the radiation field, 〈 U〉 , which is proportional to the dust-mass-weighted luminosity (LIR/Mdust) and the primary parameter defining the shape of the IR spectral energy distribution (SED), is equivalent to SFE/Z. For MS galaxies with stellar mass log (M*/M☼) ⩾ 9.7 we measure this quantity, 〈 U〉 , showing that it does not depend significantly on either the stellar mass or the sSFR. This is explained as a simple consequence of the existing correlations between SFR-M*, M*-Z, and Mgas-SFR. Instead, we show that 〈 U〉 (or equally LIR/Mdust) does evolve, with MS galaxies having harder radiation fields and thus warmer temperatures as redshift increases from z = 0 to 2, a trend that can also be understood based on the redshift evolution of the M*-Z and SFR-M* relations. These results motivate the construction of a universal set of SED templates for MS galaxies that are independent of their sSFR or M* but vary as a function of redshift with only one parameter, 〈 U〉 . [ABSTRACT FROM AUTHOR]

We present new observations from Z-Spec, a broadband 185-305 GHz spectrometer, of five submillimeter bright lensed sources selected from the Herschel-Astrophysical Terahertz Large Area Survey science demonstration phase catalog. We construct a redshift-finding algorithm using combinations of the signal to noise of all the lines falling in the Z-Spec bandpass to determine redshifts with high confidence, even in cases where the signal to noise in individual lines is low. We measure the dust continuum in all sources and secure CO redshifts for four out of five (z ∼ 1.5-3). In one source, SDP.17, we tentatively identify two independent redshifts and a water line, confirmed at z = 2.308. Our sources have properties characteristic of dusty starburst galaxies, with magnification-corrected star formation rates of 102 – 3M☼ yr–1. Lower limits for the dust masses (∼ a few 108M☼) and spatial extents (∼1 kpc equivalent radius) are derived from the continuum spectral energy distributions, corresponding to dust temperatures between 54 and 69 K. In the local thermodynamic equilibrium (LTE) approximation, we derive relatively low CO excitation temperatures (≲ 100 K) and optical depths (τ ≲ 1). Performing a non-LTE excitation analysis using RADEX, we find that the CO lines measured by Z-Spec (from J = 4 → 3 to 10 → 9, depending on the galaxy) localize the best solutions to either a high-temperature/low-density region or a low/temperature/high-density region near the LTE solution, with the optical depth varying accordingly. Observations of additional CO lines, CO(1-0) in particular, are needed to constrain the non-LTE models. [ABSTRACT FROM AUTHOR]

We present high-spatial resolution imaging obtained with the Submillimeter Array (SMA) at 880 μm and the Keck adaptive optics (AO) system at the KS-band of a gravitationally lensed submillimeter galaxy (SMG) at z = 4.243 discovered in the Herschel Astrophysical Terahertz Large Area Survey. The SMA data (angular resolution ≈0.″6) resolve the dust emission into multiple lensed images, while the Keck AO KS-band data (angular resolution ≈0.″1) resolve the lens into a pair of galaxies separated by 0.″3. We present an optical spectrum of the foreground lens obtained with the Gemini-South telescope that provides a lens redshift of zlens = 0.595 ± 0.005. We develop and apply a new lens modeling technique in the visibility plane that shows that the SMG is magnified by a factor of μ = 4.1 ± 0.2 and has an intrinsic infrared (IR) luminosity of LIR = (2.1 ± 0.2) × 1013L☼. We measure a half-light radius of the background source of rs = 4.4 ± 0.5 kpc which implies an IR luminosity surface density of ΣIR = (3.4 ± 0.9) × 1011L☼ kpc–2, a value that is typical of z > 2 SMGs but significantly lower than IR luminous galaxies at z ∼ 0. The two lens galaxies are compact (rlens ≈ 0.9 kpc) early-types with Einstein radii of θE1 = 0.57 ± 0.01 and θE2 = 0.40 ± 0.01 that imply masses of Mlens1 = (7.4 ± 0.5) × 1010M☼ and Mlens2 = (3.7 ± 0.3) × 1010M☼. The two lensing galaxies are likely about to undergo a dissipationless merger, and the mass and size of the resultant system should be similar to other early-type galaxies at z ∼ 0.6. This work highlights the importance of high spatial resolution imaging in developing models of strongly lensed galaxies discovered by Herschel. [ABSTRACT FROM AUTHOR]

We present a detailed study of the infrared spectral energy distribution of the high-redshift radio galaxy MRC 1138-26 at z = 2.156, also known as the Spiderweb Galaxy. By combining photometry from Spitzer, Herschel, and LABOCA we fit the rest-frame 5-300 μm emission using a two-component, starburst, and active galactic nucleus (AGN) model. The total infrared (8-1000 μm) luminosity of this galaxy is (1.97 ± 0.28) × 1013L☼ with (1.17 ± 0.27) and (0.79 ± 0.09) × 1013L☼ due to the AGN and starburst components, respectively. The high derived AGN accretion rate of ∼20% Eddington and the measured star formation rate (SFR) of 1390 ± 150 M☼ yr–1 suggest that this massive system is in a special phase of rapid central black hole and host galaxy growth, likely caused by a gas-rich merger in a dense environment. The accretion rate is sufficient to power both the jets and the previously observed large outflow. The high SFR and strong outflow suggest that this galaxy could potentially exhaust its fuel for stellar growth in a few tens of Myr, although the likely merger of the radio galaxy with nearby satellites suggests that bursts of star formation may recur again on timescales of several hundreds of Myr. The age of the radio lobes implies the jet started after the current burst of star formation, and therefore we are possibly witnessing the transition from a merger-induced starburst phase to a radio-loud AGN phase. We also note tentative evidence for [C II]158 μm emission. This paper marks the first results from the Herschel Galaxy Evolution Project (Project HeRGÉ), a systematic study of the evolutionary state of 71 high-redshift, 1 < z < 5.2, radio galaxies. [ABSTRACT FROM AUTHOR]

We present high-resolution maps of stars, dust, and molecular gas in a strongly lensed submillimeter galaxy (SMG) at z = 3.259. HATLAS J114637.9–001132 is selected from the Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS) as a strong lens candidate mainly based on its unusually high 500 μm flux density (∼300 mJy). It is the only high-redshift Planck detection in the 130 deg2 H-ATLAS Phase-I area. Keck Adaptive Optics images reveal a quadruply imaged galaxy in the K band while the Submillimeter Array and the Jansky Very Large Array show doubly imaged 880 μm and CO(1→0) sources, indicating differentiated distributions of the various components in the galaxy. In the source plane, the stars reside in three major kpc-scale clumps extended over ∼1.6 kpc, the dust in a compact (∼1 kpc) region ∼3 kpc north of the stars, and the cold molecular gas in an extended (∼7 kpc) disk ∼5 kpc northeast of the stars. The emissions from the stars, dust, and gas are magnified by ∼17, ∼8, and ∼7 times, respectively, by four lensing galaxies at z ∼ 1. Intrinsically, the lensed galaxy is a warm (Tdust ∼ 40-65 K), hyper-luminous (LIR ∼ 1.7 × 1013L☼; star formation rate (SFR) ∼2000 M☼ yr–1), gas-rich (Mgas/Mbaryon ∼ 70%), young (Mstellar/SFR ∼ 20 Myr), and short-lived (Mgas/SFR ∼ 40 Myr) starburst. With physical properties similar to unlensed z > 2 SMGs, HATLAS J114637.9–001132 offers a detailed view of a typical SMG through a powerful cosmic microscope. [ABSTRACT FROM AUTHOR]

We report measurements of the carbon monoxide ground state rotational transition (12C16O J = 1-0) with the Zpectrometer ultrawideband spectrometer on the 100 m diameter Green Bank Telescope. The sample comprises 11 galaxies with redshifts between z = 2.1 and 3.5 from a total sample of 24 targets identified by Herschel-ATLAS photometric colors from the SPIRE instrument. Nine of the CO measurements are new redshift determinations, substantially adding to the number of detections of galaxies with rest-frame peak submillimeter emission near 100 μm. The CO detections confirm the existence of massive gas reservoirs within these luminous dusty star-forming galaxies (DSFGs). The CO redshift distribution of the 350 μm selected galaxies is strikingly similar to the optical redshifts of 850 μm-selected submillimeter galaxies in 2.1 ⩽ z ⩽ 3.5. Spectroscopic redshifts break a temperature-redshift degeneracy; optically thin dust models fit to the far-infrared photometry indicate characteristic dust temperatures near 34 K for most of the galaxies we detect in CO. Detections of two warmer galaxies, and statistically significant nondetections, hint at warmer or molecule-poor DSFGs with redshifts that are difficult to determine from Herschel-SPIRE photometric colors alone. Many of the galaxies identified by H-ATLAS photometry are expected to be amplified by foreground gravitational lenses. Analysis of CO linewidths and luminosities provides a method for finding approximate gravitational lens magnifications μ from spectroscopic data alone, yielding μ ∼ 3-20. Corrected for magnification, most galaxy luminosities are consistent with an ultraluminous infrared galaxy classification, but three are candidate hyper-LIRGs with luminosities greater than 1013L☼. [ABSTRACT FROM AUTHOR]