ABSTRACT Numerical simulations of cosmological structure formation show that the universe's most massive clusters, and the galaxies living in those clusters, assemble rapidly at early times ( ). ...While more than 20 proto-clusters have been observed at based on associations of 5-40 galaxies around rare sources, the observational evidence for rapid cluster formation is weak. Here we report observations of an asymmetric filamentary structure at z = 2.47 containing 7 starbursting, submillimeter-luminous galaxies and 5 additional active galactic nuclei (AGNs) within a comoving volume of 15,000 Mpc3. As the expected lifetime of both the luminous AGN and starburst phase of a galaxy is ∼100 Myr, we conclude that these sources were likely triggered in rapid succession by environmental factors or, alternatively, the duration of these cosmologically rare phenomena is much longer than prior direct measurements suggest. The stellar mass already built up in the structure is ∼1012 and we estimate that the cluster mass will exceed that of the Coma supercluster at . The filamentary structure is in line with hierarchical growth simulations that predict that the peak of cluster activity occurs rapidly at .
Using Herschel data from the deepest SPIRE and PACS surveys (HerMES and PEP) in COSMOS, GOODS-S and GOODS-N, we examine the dust properties of infrared (IR)-luminous (L
IR > 1010 L) galaxies at 0.1 < ...z < 2 and determine how these evolve with cosmic time. The unique angle of this work is the rigorous analysis of survey selection effects, making this the first study of the star-formation-dominated, IR-luminous population within a framework almost entirely free of selection biases. We find that IR-luminous galaxies have spectral energy distributions (SEDs) with broad far-IR peaks characterized by cool/extended dust emission and average dust temperatures in the 25-45 K range. Hot (T > 45 K) SEDs and cold (T < 25 K), cirrus-dominated SEDs are rare, with most sources being within the range occupied by warm starbursts such as M82 and cool spirals such as M51. We observe a luminosity-temperature (L-T) relation, where the average dust temperature of log L
IR/L ∼ 12.5 galaxies is about 10 K higher than that of their log L
IR/L ∼ 10.5 counterparts. However, although the increased dust heating in more luminous systems is the driving factor behind the L-T relation, the increase in dust mass and/or starburst size with luminosity plays a dominant role in shaping it. Our results show that the dust conditions in IR-luminous sources evolve with cosmic time: at high redshift, dust temperatures are on average up to 10 K lower than what is measured locally (z 0.1). This is manifested as a flattening of the L-T relation, suggesting that (ultra)luminous infrared galaxies (U)LIRGs in the early Universe are typically characterized by a more extended dust distribution and/or higher dust masses than local equivalent sources. Interestingly, the evolution in dust temperature is luminosity dependent, with the fraction of LIRGs with T < 35 K showing a two-fold increase from z ∼ 0 to z ∼ 2, whereas that of ULIRGs with T < 35 K shows a six-fold increase. Our results suggest a greater diversity in the IR-luminous population at high redshift, particularly for ULIRGs.
Abstract
By determining the nature of all the Planck compact sources within 808.4 deg2 of large Herschel surveys, we have identified 27 candidate protoclusters of dusty star-forming galaxies (DSFGs) ...that are at least 3σ overdense in either 250, 350, or 500 $\mu$m sources. We find roughly half of all the Planck compact sources are resolved by Herschel into multiple discrete objects, with the other half remaining unresolved by Herschel. We find a significant difference between versions of the Planck catalogues, with earlier releases hosting a larger fraction of candidate protoclusters and Galactic cirrus than later releases, which we ascribe to a difference in the filters used in the creation of the three catalogues. We find a surface density of DSFG candidate protoclusters of (3.3 ± 0.7) × 10−2 sources deg−2, in good agreement with previous similar studies. We find that a Planck colour selection of S857/S545 < 2 works well to select candidate protoclusters, but can miss protoclusters at z < 2. The Herschel colours of individual candidate protocluster members indicate our candidate protoclusters all likely all lie at z > 1. Our candidate protoclusters are a factor of 5 times brighter at 353 GHz than expected from simulations, even in the most conservative estimates. Further observations are needed to confirm whether these candidate protoclusters are physical clusters, multiple protoclusters along the line of sight, or chance alignments of unassociated sources.
ABSTRACT We present an improved and extended analysis of the cross-correlation between the map of the cosmic microwave background (CMB) lensing potential derived from the Planck mission data and the ...high-redshift galaxies detected by the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) in the photometric redshift range . We compare the results based on the 2013 and 2015 Planck datasets, and investigate the impact of different selections of the H-ATLAS galaxy samples. Significant improvements over our previous analysis have been achieved thanks to the higher signal-to-noise ratio of the new CMB lensing map recently released by the Planck collaboration. The effective galaxy bias parameter, b, for the full galaxy sample, derived from a joint analysis of the cross-power spectrum and of the galaxy auto-power spectrum is found to be . Furthermore, a first tomographic analysis of the cross-correlation signal is implemented by splitting the galaxy sample into two redshift intervals: and . A statistically significant signal was found for both bins, indicating a substantial increase with redshift of the bias parameter: for the lower and for the higher redshift bin. Consistent with our previous analysis, we find that the amplitude of the cross-correlation signal is a factor of higher than expected from the standard ΛCDM model for the assumed redshift distribution. The robustness of our results against possible systematic effects has been extensively discussed, although the tension is mitigated by passing from 4 to 3 .
We study a sample of Herschel selected galaxies within the Great Observatories Origins Deep Survey-South and the Cosmic Evolution Survey fields in the framework of the Photodetector Array Camera and ...Spectrometer (PACS) Evolutionary Probe project. Starting from the rich multiwavelength photometric data sets available in both fields, we perform a broad-band spectral energy distribution decomposition to disentangle the possible active galactic nucleus (AGN) contribution from that related to the host galaxy. We find that 37 per cent of the Herschel-selected sample shows signatures of nuclear activity at the 99 per cent confidence level. The probability of revealing AGN activity increases for bright (L
1−1000 > 1011
L
) star-forming galaxies at z > 0.3, becoming about 80 per cent for the brightest (L
1−1000 > 1012
L
) infrared (IR) galaxies at z ≥ 1. Finally, we reconstruct the AGN bolometric luminosity function and the supermassive black hole growth rate across cosmic time up to z ∼ 3 from a far-IR perspective. This work shows general agreement with most of the panchromatic estimates from the literature, with the global black hole growth peaking at z ∼ 2 and reproducing the observed local black hole mass density with consistent values of the radiative efficiency rad (∼0.07).
Exploiting the Herschel Astrophysical Terahertz Large Area Survey Science Demonstration Phase survey data, we have determined the luminosity functions (LFs) at rest-frame wavelengths of 100 and 250 ...Delta *mm and at several redshifts z 1, for bright submillimeter galaxies with star formation rates (SFRs) 100 M yr--1. We find that the evolution of the comoving LF is strong up to z 2.5, and slows down at higher redshifts. From the LFs and the information on halo masses inferred from clustering analysis, we derived an average relation between SFR and halo mass (and its scatter). We also infer that the timescale of the main episode of dust-enshrouded star formation in massive halos (M H 3 X 1012 M ) amounts to ~7 X 108 yr. Given the SFRs, which are in the range of 102-103 M yr--1, this timescale implies final stellar masses of the order of 1011-1012 M . The corresponding stellar mass function matches the observed mass function of passively evolving galaxies at z 1. The comparison of the statistics for submillimeter and UV-selected galaxies suggests that the dust-free, UV bright phase is 102 times shorter than the submillimeter bright phase, implying that the dust must form soon after the onset of star formation. Using a single reference spectral energy distribution (SED; the one of the z 2.3 galaxy SMM J2135-0102), our simple physical model is able to reproduce not only the LFs at different redshifts >1 but also the counts at wavelengths ranging from 250 Delta *mm to 1 mm. Owing to the steepness of the counts and their relatively broad frequency range, this result suggests that the dispersion of submillimeter SEDs of z > 1 galaxies around the reference one is rather small.
ABSTRACT
We present SCUBA-2 850 $\mathrm{ \mu}$m observations of 13 candidate starbursting protoclusters selected using Planck and Herschel data. The cumulative number counts of the 850 $\mathrm{ ...\mu}$m sources in 9 of 13 of these candidate protoclusters show significant overdensities compared to the field, with the probability <10−2 assuming the sources are randomly distributed in the sky. Using the 250, 350, 500, and 850 $\mathrm{ \mu}$m flux densities, we estimate the photometric redshifts of individual SCUBA-2 sources by fitting spectral energy distribution templates with an MCMC method. The photometric redshift distribution, peaking at 2 < z < 3, is consistent with that of known z > 2 protoclusters and the peak of the cosmic star formation rate density (SFRD). We find that the 850 $\mathrm{ \mu}$m sources in our candidate protoclusters have infrared luminosities of $L_{\mathrm{IR}}\gtrsim 10^{12}\, \mathrm{L}_{\odot }$ and star formation rates of SFR = (500–1500) M⊙ yr−1. By comparing with results in the literature considering only Herschel photometry, we conclude that our 13 candidate protoclusters can be categorized into four groups: six of them being high-redshift starbursting protoclusters, one being a lower redshift cluster or protocluster, three being protoclusters that contain lensed dusty star-forming galaxies or are rich in 850 $\mathrm{ \mu}$m sources, and three regions without significant Herschel or SCUBA-2 source overdensities. The total SFRs of the candidate protoclusters are found to be comparable or higher than those of known protoclusters, suggesting our sample contains some of the most extreme protocluster population. We infer that cross-matching Planck and Herschel data is a robust method for selecting candidate protoclusters with overdensities of 850 $\mathrm{ \mu}$m sources.
Abstract
We present the calibration between the dust continuum luminosity and interstellar gas content obtained from the Valparaíso ALMA Line Emission Survey (VALES) sample of 67 main-sequence ...star-forming galaxies at 0.02 < z < 0.35. We use CO(1–0) observations from the Atacama Large Millimetre/submillimetre Array to trace the molecular gas mass, M
H
2, and estimate the rest-frame monochromatic luminosity at 850 μm,
$L_{\nu _{850}}$
, by extrapolating the dust continuum from magphys modelling of the far-ultraviolet to submillimetre spectral energy distribution sampled by the Galaxy And Mass Assembly survey. Adopting αCO = 6.5 (K km s−1 pc2)−1, the average ratio of
$L_{\nu _{850}}$
/M
H
2 = (6.4 ± 1.4)× 1019 erg s−1 Hz−1 M
$_{{\odot }}^{-1}$
, in excellent agreement with literature values. We obtain a linear fit of
$\log _{10} \left({M}_{\mathrm{H}_{2}}/{\mathrm{M}_{{\odot }}}\right) = (0.92\pm 0.02) \log _{10} (L_{\nu _{850}}/{\mathrm{erg}\,\mathrm{s}^{-1}\,\mathrm{Hz}^{-1}})-(17.31\pm 0.59)$
. We provide relations between
$L_{\nu _{850}}$
, M
H
2 and M
ISM when combining the VALES and literature samples, and adopting a Galactic αCO value.
Context. Since the mid-1990s, the sample of Lyman-break galaxies (LBGs) has been growing thanks to the increasing sensitivities in the optical and in near-infrared telescopes for objects at z> 2.5. ...However, the dust properties of the LBGs are poorly known because the samples are small and/or biased against far-infrared (far-IR) or submillimeter (submm) observations. Aims. This work explores from a statistical point of view the far-IR and submm properties of a large sample of LBGs at z ~ 3 that cannot be individually detected from current far-IR observations. Methods. We select a sample of 22, 000 LBGs at 2.5 <z< 3.5 in the COSMOS field using the dropout technique. The large number of galaxies included in the sample allows us to split it into several bins as a function of UV luminosity (LFUV), UV continuum slope (βUV), and stellar mass (M∗) to better sample their variety. We stack in PACS (100 and 160 μm) images from PACS Evolution Probe survey (PEP), SPIRE (250, 350 and 500 μm) images from the Herschel Multi-tied Extragalactic Survey (HerMES) programs, and AzTEC (1.1 mm) images from the Atacama Submillimeter Telescope Experiment (ASTE). Our stacking procedure corrects the biases induced by galaxy clustering and incompleteness of our input catalogue in dense regions. Results. We obtain the full infrared spectral energy distributions (SED) of subsamples of LBGs and derive the mean IR luminosity as a function of LFUV, βUV, and M∗. The average IRX (or dust attenuation) is roughly constant over the LFUV range, with a mean of 7.9 (1.8 mag). However, it is correlated with βUV, AFUV = (3.15 ± 0.12) + (1.47 ± 0.14) βUV, and stellar mass, log (IRX) = (0.84 ± 0.11)log (M∗/ 1010.35) + 1.17 ± 0.05. We investigate using a statistically controlled stacking analysis as a function of (M∗, βUV), the dispersion of the IRX-βUV and IRX-M∗ plane. On the one hand, the dust attenuation shows a departure of up to 2.8 mag above the mean IRX-βUV relation when log (M∗ M⊙ ) increases from 9.75 to 11.5 in the same βUV bin. This strongly suggests that M∗ plays an important role in shaping the IRX-βUV plane. On the other hand, the IRX-M∗ plane is less dispersed for variation in the βUV. However, the dust attenuation shows a departure of up to 1.3 mag above the mean IRX-M∗ relation, when βUV increases from −1.7 to 0.5 in the same M∗ bin. The low stellar mass LBGs (log (M∗ M⊙ ) < 10.5) and red βUV (βUV> −0.7), 15% of the total sample, present a high dust attenuation than the mean IRX-M∗, but they are still in agreement with the mean IRX-βUV relation. We suggest that we have to combine both the IRX-βUV and IRX-M∗ relations to obtain the best estimation of the dust attenuation from the UV and NIR properties of the galaxies (LFUV, βUV, M∗). Our results enable us to study the average relation between star formation rate (SFR) and stellar mass, and we show that our LBG sample lies on the main sequence of star formation at z ~ 3. we demonstrate that the SFR is underestimate for LBGs with high stellar mass, but it give a good estimation for LBGs with lower stellar mass when we calculate the SFR by correcting the LFUV using the IRX-βUV relation.
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