Abstract
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 data set spanning a broad range in stellar-mass (108–1012 M⊙), dust-mass (106–109 M⊙), and star formation rates (0.01–100 M⊙yr−1), 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 data set 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 CSFH we precisely reproduce the SMD
with an interstellar medium replenishment factor of 0.50 ± 0.07, consistent with our choice of Chabrier initial mass function 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 90–95 per cent of all dust formed has been destroyed and/or ejected.
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 deg2 with the PACS and ...SPIRE cameras in five photometric bands: 100, 160, 250, 350, and 500 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 deg2 in size, centered on the north Galactic pole (NGP), and the second is 317.6 deg2 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−1 at 100 and 160 m, and 11.0, 11.1 and 12.3 mJy beam−1 at 250, 350 and 500 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 map sensitivity is 5.7, 6.0, and 7.3 mJy at 250, 350, and 500 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−1 at 250, 350, and 500 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−1 at 100 and 160 m. Finally, we give recipes for using these images to carry out photometry, both for unresolved and extended sources.
Interstellar dust in galaxies can be traced either through its extinction effects on the star light or through its thermal emission at infrared wavelengths. Recent radiative transfer studies of ...several nearby edge-on galaxies have found an apparent inconsistency in the dust energy balance: the radiative transfer models that successfully explain the optical extinction underestimate the observed fluxes by an average factor of 3. We investigate the dust energy balance for IC 4225 and NGC 5166, two edge-on spiral galaxies observed by the Herschel Space Observatory in the frame of the H-ATLAS survey. We start from models which were constrained from optical data and extend them to construct the entire spectral energy distribution of our galaxies. These predicted values are subsequently compared to the observed far-infrared fluxes. We find that including a young stellar population in the modelling is necessary as it plays a non-negligible part in the heating of the dust grains. While the modelling approach for both galaxies is nearly identical, we find two very different results. As is often seen in other edge-on spiral galaxies, the far-infrared emission of our radiative transfer model of IC 4225 underestimates the observed fluxes by a factor of about 3. For NGC 5166 on the other hand, we find that both the predicted spectral energy distribution as well as the simulated images match the observations particularly well. We explore possible reasons for this difference and conclude that it is unlikely that one single mechanism is the cause of the dust energy balance problem in spiral galaxies. We discuss the different approaches that can be considered in order to get a conclusive answer on the origin this discrepancy.
The clustering properties of local, S1.4 GHz≥ 1 mJy, radio sources are investigated for a sample of 820 objects drawn from the joint use of the Faint Images of the Radio Sky at 20 cm (FIRST) and 2dF ...Galaxy Redshift surveys. To this aim, we present 271 new bJ≤ 19.45 spectroscopic counterparts of FIRST radio sources to be added to those already introduced in our previous paper. The two-point correlation function for the local radio population is found to be entirely consistent with estimates obtained for the whole sample of 2dFGRS galaxies. From measurements of the redshift-space correlation function ξ(s) we derive a redshift-space clustering length s0 = 10.7+0.8 −0.7 Mpc, while from the projected correlation function Ξ(rT) we estimate the parameters of the real-space correlation function ξ(r) = (r/r0) −γ, r0 = 6.7+0.9 −1.1 Mpc and γ= 1.6 ± 0.1, where h = 0.7 is assumed. Different results are instead obtained if we only consider sources that present signatures of active galactic nucleus (AGN) activity in their spectra. These objects are shown to be very strongly correlated, with r0 = 10.9+1.0 −1.2 Mpc and γ= 2 ± 0.1, a steeper slope than has been claimed in other recent works. No difference is found in the clustering properties of radio-AGNs of different radio luminosity. Comparisons with models for ξ(r) show that AGN-fuelled sources reside in dark matter haloes more massive than ∼1013.4 M⊙, higher than the corresponding figure for radio-quiet quasi-stellar objects. This value can be converted into a minimum black hole mass associated with radio-loud, AGN-fuelled objects of MminBH∼ 109 M⊙. The above results then suggest – at least for relatively faint radio objects – the existence of a threshold black hole mass associated with the onset of significant radio activity such as that of radio-loud AGNs; however, once the activity is triggered, there appears to be no evidence for a connection between black hole mass and level of radio output.
We describe the infrared properties of sources detected over ~36 deg super(2) of sky in the GAMA 15 hr equatorial field, using data from both the Herschel Astrophysical Terahertz Large-Area Survey ...(H-ATLAS) and Wide-field Infrared Survey (WISE). With 5sigma point-source depths of 34 and 0.048 mJy at 250 mu m and 3.4 mu m, respectively, we are able to identify 50.6% of the H-ATLAS sources in the WISE survey, corresponding to a surface density of ~630 deg super(-2). Approximately two-thirds of these sources have measured spectroscopic or optical/near-IR photometric redshifts of z < 1. For sources with spectroscopic redshifts at z < 0.3, we find a linear correlation between the infrared luminosity at 3.4 mu m and that at 250 mu m, with + or -50% scatter over ~1.5 orders of magnitude in luminosity, ~10 super(9)-10 super(10.5) L sub(middot in circle). By contrast, the matched sources without previously measured redshifts (r > ~ 20.5) have 250-350 mu m flux density ratios which suggest either high-redshift galaxies (z > ~ 1.5) or optically faint low-redshift galaxies with unusually low temperatures (T > ~ 20). Their small 3.4-250 mu m flux ratios favor a high-redshift galaxy population, as only the most actively star-forming galaxies at low redshift (e.g., Arp 220) exhibit comparable flux density ratios. Furthermore, we find a relatively large active galactic nucleus fraction (~30%) in a 12 mu m flux-limited subsample of H-ATLAS sources, also consistent with there being a significant population of high-redshift sources in the no-redshift sample.
We use redshift determinations and spectral analysis of galaxies in the 2dF Galaxy Redshift Survey to study the properties of local radio sources with S≥1 mJy. 557 objects (hereafter called the ...spectroscopic sample) drawn from the FIRST survey, corresponding to 2.3 per cent of the total radio sample, are found in the 2dFGRS catalogue within the area 9h48m≲RA(2000)≲14h32m and -277≲Dec.(2000)≲225, down to a magnitude limit bJ=19.45. The excellent quality of 2dF spectra allows us to divide these sources into classes, according to their optical spectra. Absorption-line systems make up 63 per cent of the spectroscopic sample. These may or may not show emission lines due to AGN activity, and correspond to ‘classical’ radio galaxies belonging mainly to the FRI class. They are characterized by relatively high radio-to-optical ratios, red colours, and high radio luminosities (1021≲P1.4 GHz/W Hz-1 sr-1≲1024). Actively star-forming galaxies contribute about 32 per cent of the sample. These objects are mainly found at low redshifts (z≲0.1) and show low radio-to-optical ratios, blue colours and low radio luminosities. We also found 18 Seyfert 2 galaxies (3 per cent) and four Seyfert 1s (1 per cent). Analysis of the local radio luminosity function (LF) shows that radio galaxies are well described by models that assume pure luminosity evolution, at least down to radio powers P1.4 GHz≲1020.5 W Hz-1 sr-1. Late-type galaxies, whose relative contribution to the radio LF is found to be lower than was predicted by previous works, present an LF which is comparable with the IRAS galaxy LF. This class of sources therefore plausibly constitutes the radio counterpart of the dusty spirals and starbursts that dominate the counts at 60 μm.
Herschel -ATLAS and ALMA Messias, Hugo; Dye, Simon; Nagar, Neil ...
Astronomy and astrophysics (Berlin),
08/2014, Letnik:
568
Journal Article
Recenzirano
Odprti dostop
Context. The submillimetre-bright galaxy population is believed to comprise, aside from local galaxies and radio-loud sources, intrinsically active star-forming galaxies, the brightest of which are ...lensed gravitationally. The latter enable studies at a level of detail beyond what is usually possible by the observation facility. Aims: This work focuses on one of these lensed systems, HATLAS J142935.3-002836 (H1429-0028), selected in the Herschel-ATLAS field. Gathering a rich, multi-wavelength dataset, we aim to confirm the lensing hypothesis and model the background source's morphology and dynamics, as well as to provide a full physical characterisation. Methods: Multi-wavelength high-resolution data is utilised to assess the nature of the system. A lensing-analysis algorithm that simultaneously fits different wavebands is adopted to characterise the lens. The background galaxy dynamical information is studied by reconstructing the 3D source plane of the ALMA CO (J:4 → 3) transition. Near-IR imaging from HST and Keck-AO allows to constrain rest-frame optical photometry independently for the foreground and background systems. Physical parameters (such as stellar and dust masses) are estimated via modelling of the spectral energy distribution taking source blending, foreground obscuration, and differential magnification into account. Results: The system comprises a foreground edge-on disk galaxy (at zsp = 0.218) with an almost complete Einstein ring around it. The background source (at zsp = 1.027) is magnified by a factor of μ ~ 8-10 depending on wavelength. It is comprised of two components and a tens-of-kpc-long tidal tail resembling the Antennæ merger. As a whole, the background source is a massive stellar system (1.32-0.41+ 0.63 × 1011 M⊙) forming stars at a rate of 394 ± 90 M⊙ yr-1, and it has a significant gas reservoir MISM = 4.6 ± 1.7 × 1010 M⊙. Its depletion time due to star formation alone is thus expected to be τSF = MISM/ SFR = 117 ± 51 Myr. The dynamical mass of one of the components is estimated to be 5.8 ± 1.7 × 1010 M⊙, and, together with the photometric total mass estimate, it implies that H1429-0028 is a major merger system (1:2.8-1.5+1.8).
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