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 \emph{Planck} mission data and the ...high-redshift galaxies detected by the \emph{Herschel} Astrophysical Terahertz Large Area Survey (H-ATLAS) in the photometric redshift range \(z_{\rm ph} \ge 1.5\). We compare the results based on the 2013 and 2015 \textit{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 \textit{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 \(b = 3.54^{+0.15}_{-0.14}\). Furthermore, a first tomographic analysis of the cross-correlation signal is implemented, by splitting the galaxy sample into two redshift intervals: \(1.5 \le z_{\rm ph} < 2.1\) and \(z_{\rm ph}\ge 2.1\). A statistically significant signal was found for both bins, indicating a substantial increase with redshift of the bias parameter: \(b=2.89\pm0.23\) for the lower and \(b=4.75^{+0.24}_{-0.25}\) for the higher redshift bin. Consistently with our previous analysis we find that the amplitude of the cross correlation signal is a factor of \(1.45^{+0.14}_{-0.13}\) higher than expected from the standard \(\Lambda\)CDM 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\(\sigma\).
The galaxies found in optical surveys fall in two distinct regions of a diagram of optical colour versus absolute magnitude: the red sequence and the blue cloud with the green valley in between. We ...show that the galaxies found in a submillimetre survey have almost the opposite distribution in this diagram, forming a `green mountain'. We show that these distinctive distributions follow naturally from a single, continuous, curved Galaxy Sequence in a diagram of specific star-formation rate versus stellar mass without there being the need for a separate star-forming galaxy Main Sequence and region of passive galaxies. The cause of the red sequence and the blue cloud is the geometric mapping between stellar mass/specific star-formation rate and absolute magnitude/colour, which distorts a continuous Galaxy Sequence in the diagram of intrinsic properties into a bimodal distribution in the diagram of observed properties. The cause of the green mountain is Malmquist bias in the submillimetre waveband, with submillimetre surveys tending to select galaxies on the curve of the Galaxy Sequence, which have the highest ratios of submillimetre-to-optical luminosity. This effect, working in reverse, causes galaxies on the curve of the Galaxy Sequence to be underrepresented in optical samples, deepening the green valley. The green valley is therefore not evidence (1) for there being two distinct populations of galaxies, (2) for galaxies in this region evolving more quickly than galaxies in the blue cloud and the red sequence, (c) for rapid quenching processes in the galaxy population.
Radio emission is a key indicator of star-formation activity in galaxies, but the radio luminosity-star formation relation has to date been studied almost exclusively at frequencies of 1.4 GHz or ...above. At lower radio frequencies the effects of thermal radio emission are greatly reduced, and so we would expect the radio emission observed to be completely dominated by synchrotron radiation from supernova-generated cosmic rays. As part of the LOFAR Surveys Key Science project, the Herschel-ATLAS NGP field has been surveyed with LOFAR at an effective frequency of 150 MHz. We select a sample from the MPA-JHU catalogue of SDSS galaxies in this area: the combination of Herschel, optical and mid-infrared data enable us to derive star-formation rates (SFRs) for our sources using spectral energy distribution fitting, allowing a detailed study of the low-frequency radio luminosity--star-formation relation in the nearby Universe. For those objects selected as star-forming galaxies (SFGs) using optical emission line diagnostics, we find a tight relationship between the 150 MHz radio luminosity (\(L_{150}\)) and SFR. Interestingly, we find that a single power-law relationship between \(L_{150}\) and SFR is not a good description of all SFGs: a broken power law model provides a better fit. This may indicate an additional mechanism for the generation of radio-emitting cosmic rays. Also, at given SFR, the radio luminosity depends on the stellar mass of the galaxy. Objects which were not classified as SFGs have higher 150-MHz radio luminosity than would be expected given their SFR, implying an important role for low-level active galactic nucleus activity.
We present the largest submillimeter images that have been made of the extragalactic sky. The Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) is a survey of 660 deg\(^2\) with the PACS ...and SPIRE cameras in five photometric bands: 100, 160, 250, 350, and 500{\mu}m. In this paper we present the images from our two largest fields which account for ~75% of the survey. The first field is 180.1 deg\(^2\) in size centered on the North Galactic Pole (NGP) and the second field is 317.6 deg\(^2\) in size centered on the South Galactic Pole. The NGP field serendipitously contains the Coma cluster. Over most (~80%) of the images, the pixel noise, including both instrumental noise and confusion noise, is approximately 3.6, and 3.5 mJy/pix at 100 and 160{\mu}m, and 11.0, 11.1 and 12.3 mJy/beam at 250, 350 and 500{\mu}m, respectively, but reaches lower values in some parts of the images. If a matched filter is applied to optimize point-source detection, our total 1{\sigma} map sensitivity is 5.7, 6.0, and 7.3 mJy at 250, 350, and 500{\mu}m, respectively. We describe the results of an investigation of the noise properties of the images. We make the most precise estimate of confusion in SPIRE maps to date finding values of 3.12+/-0.07, 4.13+/-0.02 and 4.45+/-0.04 mJy/beam at 250, 350, and 500{\mu}m in our un-convolved maps. For PACS we find an estimate of the confusion noise in our fast-parallel observations of 4.23 and 4.62 mJy/beam at 100 and 160{\mu}m. Finally, we give recipes for using these images to carry out photometry, both for unresolved and extended sources.
The Herschel Space Observatory has revealed a very different galaxyscape from that shown by optical surveys which presents a challenge for galaxy-evolution models. The Herschel surveys reveal (1) ...that there was rapid galaxy evolution in the very recent past and (2) that galaxies lie on a a single Galaxy Sequence (GS) rather than a star-forming `main sequence' and a separate region of `passive' or `red-and-dead' galaxies. The form of the GS is now clearer because far-infrared surveys such as the Herschel ATLAS pick up a population of optically-red star-forming galaxies that would have been classified as passive using most optical criteria. The space-density of this population is at least as high as the traditional star-forming population. By stacking spectra of H-ATLAS galaxies over the redshift range 0.001 < z < 0.4, we show that the galaxies responsible for the rapid low-redshift evolution have high stellar masses, high star-formation rates but, even several billion years in the past, old stellar populations - they are thus likely to be relatively recent ancestors of early-type galaxies in the Universe today. The form of the GS is inconsistent with rapid quenching models and neither the analytic bathtub model nor the hydrodynamical EAGLE simulation can reproduce the rapid cosmic evolution. We propose a new gentler model of galaxy evolution that can explain the new Herschel results and other key properties of the galaxy population.
We present the evolution of the Cosmic Spectral Energy Distribution (CSED) from \(z = 1 - 0\). Our CSEDs originate from stacking individual spectral energy distribution fits based on panchromatic ...photometry from the Galaxy and Mass Assembly (GAMA) and COSMOS datasets in ten redshift intervals with completeness corrections applied. Below \(z = 0.45\), we have credible SED fits from 100 nm to 1 mm. Due to the relatively low sensitivity of the far-infrared data, our far-infrared CSEDs contain a mix of predicted and measured fluxes above \(z = 0.45\). Our results include appropriate errors to highlight the impact of these corrections. We show that the bolometric energy output of the Universe has declined by a factor of roughly four -- from \(5.1 \pm 1.0\) at \(z \sim 1\) to \(1.3 \pm 0.3 \times 10^{35}~h_{70}\)~W~Mpc\(^{-3}\) at the current epoch. We show that this decrease is robust to cosmic variance, SED modelling and other various types of error. Our CSEDs are also consistent with an increase in the mean age of stellar populations. We also show that dust attenuation has decreased over the same period, with the photon escape fraction at 150~nm increasing from \(16 \pm 3\) at \(z \sim 1\) to \(24 \pm 5\) per cent at the current epoch, equivalent to a decrease in \(A_\mathrm{FUV}\) of 0.4~mag. Our CSEDs account for \(68 \pm 12\) and \(61 \pm 13\) per cent of the cosmic optical and infrared backgrounds respectively as defined from integrated galaxy counts and are consistent with previous estimates of the cosmic infrared background with redshift.
Submillimeter galaxies (SMGs) at \(z\gtrsim1\) are luminous in the far-infrared and have star-formation rates, SFR, of hundreds to thousands of solar masses per year. However, it is unclear whether ...they are true analogs of local ULIRGs or whether the mode of their star formation is more similar to that in local disk galaxies. We target these questions by using Herschel-PACS to examine the conditions in the interstellar medium (ISM) in far-infrared luminous SMGs at z~1-4. We present 70-160 micron photometry and spectroscopy of the OIV26 micron, FeII26 micron, SIII33 micron, SiII34 micron, OIII52 micron, NIII57 micron, and OI63 micron fine-structure lines and the S(0) and S(1) hydrogen rotational lines in 13 lensed SMGs identified by their brightness in early Herschel data. Most of the 13 targets are not individually spectroscopically detected and we instead focus on stacking these spectra with observations of an additional 32 SMGs from the \herschel\ archive -- representing a complete compilation of PACS spectroscopy of SMGs. We detect OI63 micron, SiII34 micron, and NIII57 micron at >3sigma in the stacked spectra, determining that the average strengths of these lines relative to the far-IR continuum are \((0.36\pm0.12)\times10^{-3}\), \((0.84\pm0.17)\times10^{-3}\), and \((0.27\pm0.10)\times10^{-3}\), respectively. Using the OIII52/NIII57 emission line ratio we show that SMGs have average gas-phase metallicities \(\gtrsim Z_{\rm sun}\). By using PDR modelling and combining the new spectral measurements with integrated far-infrared fluxes and existing CII158 micron data we show that SMGs have average gas densities, n, of \(\sim10^{1-3}{\rm cm^{-3}}\) and FUV field strengths, \(G_0\sim10^{2.2-4.5}\) (in Habing units: \(1.6\times10^{-3}{\rm erg~cm^{-2}~s^{-1}}\)), consistent with both local ULIRGs and lower luminosity star-forming galaxies.
We use the energy-balance code MAGPHYS to determine stellar and dust masses, and dust corrected star-formation rates for over 200,000 GAMA galaxies, 170,000 G10-COSMOS galaxies and 200,000 3D-HST ...galaxies. Our values agree well with previously reported measurements and constitute a representative and homogeneous dataset spanning a broad range in stellar mass (10^8---10^12 Msol), dust mass (10^6---10^9 Msol), and star-formation rates (0.01---100 Msol per yr), and over a broad redshift range (0.0 < z < 5.0). We combine these data to measure the cosmic star-formation history (CSFH), the stellar-mass density (SMD), and the dust-mass density (DMD) over a 12 Gyr timeline. The data mostly agree with previous estimates, where they exist, and provide a quasi-homogeneous dataset using consistent mass and star-formation estimators with consistent underlying assumptions over the full time range. As a consequence our formal errors are significantly reduced when compared to the historic literature. Integrating our cosmic star-formation history we precisely reproduce the stellar-mass density with an ISM replenishment factor of 0.50 +/- 0.07, consistent with our choice of Chabrier IMF plus some modest amount of stripped stellar mass. Exploring the cosmic dust density evolution, we find a gradual increase in dust density with lookback time. We build a simple phenomenological model from the CSFH to account for the dust mass evolution, and infer two key conclusions: (1) For every unit of stellar mass which is formed 0.0065---0.004 units of dust mass is also formed; (2) Over the history of the Universe approximately 90 to 95 per cent of all dust formed has been destroyed and/or ejected.
The SCUBA-2 Ultra Deep Imaging EAO Survey (STUDIES) is a three-year JCMT Large Program aiming at reaching the 450 \(\mu\)m confusion limit in the COSMOS-CANDELS region, to study a representative ...sample of the high-redshift far-infrared galaxy population that gives rise to the bulk of the far-infrared background. We present the first-year data from STUDIES. We have reached a 450 \(\mu\)m noise level of 0.91~mJy for point sources at the map center, covered an area of 151 arcmin\(^2\), and detected 98 and 141 sources at 4.0 and 3.5 \(\sigma\), respectively. Our derived counts are best constrained in the 3.5-25 mJy regime using directly detected sources. Below the detection limits, our fluctuation analysis further constrains the slope of the counts down to 1 mJy. The resulting counts at 1-25 mJy are consistent with a power law having a slope of \(-2.59\) (\(\pm0.10\) for 3.5-25 mJy, and \(^{+0.4}_{-0.7}\) for 1-3.5 mJy). There is no evidence of a faint-end termination or turn-over of the counts in this flux density range. Our counts are also consistent with previous SCUBA-2 blank-field and lensing cluster surveys. The integrated surface brightness from our counts down to 1 mJy is \(90.0\pm17.2\) Jy deg\(^{-2}\), which can account for up to \(83^{+15}_{-16}\%\) of the COBE 450 \(\mu\)m background. We show that Herschel counts at 350 and 500 \(\mu\)m are significantly higher than our 450 \(\mu\)m counts, likely caused by its large beam and source clustering. High-angular resolution instruments like SCUBA-2 at 450 \(\mu\)m are therefore highly beneficial for measuring the luminosity and spatial density of high-redshift dusty galaxies.
