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 a catalogue of ALMA flux density measurements of 754 calibrators observed between 2012 August and 2017 September, for a total of 16263 observations in different bands and epochs. ...The flux densities were measured by reprocessing the ALMA images generated in the framework of the ALMACAL project, with a new code developed by the Italian node of the European ALMA Regional Centre. A search in the online data bases yielded redshift measurements for 589 sources (∼78 per cent of the total). Almost all sources are flat spectrum, based on their low-frequency spectral index, and have properties consistent with being blazars of different types. To illustrate the properties of the sample, we show the redshift and flux density distributions as well as the distributions of the number of observations of individual sources and of timespans in the source frame for sources observed in bands 3 (84−116 GHz) and 6 (211−275 GHz). As examples of the scientific investigations allowed by the catalogue, we briefly discuss the variability properties of our sources in ALMA bands 3 and 6 and the frequency spectra between the effective frequencies of these bands. We find that the median variability index steadily increases with the source-frame time lag increasing from 100 to 800 d, and that the frequency spectra of BL Lacs are significantly flatter than those of flat-spectrum radio quasars. We also show the global spectral energy distributions of our sources over 17 orders of magnitude in frequency.
The shallow, all-sky
Planck
surveys at sub-millimetre wavelengths have detected the brightest strongly gravitationally lensed dusty galaxies in the sky. The combination of their extreme gravitational ...flux-boosting and image-stretching offers the unique possibility of measuring in extraordinary detail the galaxy structure and kinematics in early evolutionary phases through high-resolution imaging and spectroscopic follow-up. This enables us to gain otherwise unaccessible direct information on physical processes in action. However, the extraction of candidate strongly lensed galaxies from
Planck
catalogues is hindered by the fact that they are generally detected with a poor signal-to-noise ratio, except for the few brightest galaxies. Their photometric properties are therefore strongly blurred, which makes them very difficult to single out. We have devised a method capable of increasing the number of identified
Planck
-detected strongly lensed galaxies by a factor of about three to four, although with an unavoidably limited efficiency. Our approach exploits the fact that the sub-millimetre colours of strongly lensed galaxies are definitely colder than those of nearby dusty galaxies, which constitute the overwhelming majority of extragalactic sources detected by
Planck
. The sub-millimetre colours of the 47 confirmed or very likely
Planck
-detected strongly lensed galaxies have been used to estimate the colour range spanned by objects of this type. Moreover, most nearby galaxies and radio sources can be confirmed by cross-matching with the IRAS and PCNT catalogues, respectively. We present samples of lensed candidates selected at 545, 857, and 353 GHz, comprising 177, 97, and 104 sources, respectively. The efficiency of our approach, tested by exploiting data from the SPT survey covering ≃2500 deg
2
, is estimated to be in the range 30%−40%. We also discuss stricter selection criteria to increase the estimated efficiency to ≃50%, at the cost of a somewhat lower completeness. Our analysis of SPT data has identified a dozen galaxies that can reliably be considered previously unrecognized
Planck
-detected strongly lensed galaxies. Extrapolating the number of
Planck
-detected confirmed or very likely strongly lensed galaxies found within the SPT and H-ATLAS survey areas, we expect ≃150 to ≃190 such sources over the full |
b
|> 20° sky.
ABSTRACT
We present the ALMA view of 11 main-sequence dusty star-forming galaxies (DSFGs) (sub-)millimetre selected in the Great Observatories Origins Survey South (GOODS-S) field and ...spectroscopically confirmed to be at the peak of cosmic star formation history (z ∼ 2). Our study combines the analysis of galaxy spectral energy distribution with ALMA continuum and CO spectral emission by using ALMA Science Archive products at the highest spatial resolution currently available for our sample (Δθ ≲ 1 arcsec). We include galaxy multiband images and photometry (in the optical, radio, and X-rays) to investigate the interlink between dusty, gaseous, and stellar components and the eventual presence of AGN. We use multiband sizes and morphologies to gain an insight on the processes that lead galaxy evolution, e.g. gas condensation, star formation, AGN feedback. The 11 DSFGs are very compact in the (sub-)millimetre (median rALMA = 1.15 kpc), while the optical emission extends to larger radii (median rH/rALMA = 2.05). CO lines reveal the presence of a rotating disc of molecular gas, but we cannot exclude the presence of interactions and/or molecular outflows. Images at higher (spectral and spatial) resolution are needed to disentangle from the possible scenarios. Most of the galaxies are caught in the compaction phase, when gas cools and falls into galaxy centre, fuelling the dusty burst of star formation and the growing nucleus. We expect these DSFGs to be the high-z star-forming counterparts of massive quiescent galaxies. Some features of CO emission in three galaxies are suggestive of forthcoming/ongoing AGN feedback, which is thought to trigger the morphological transition from star-forming discs to early-type galaxies.
ALMA photometry of extragalactic radio sources Bonato, M; Liuzzo, E; Herranz, D ...
Monthly notices of the Royal Astronomical Society,
05/2019, Letnik:
485, Številka:
1
Journal Article
We present the Planck Sky Model (PSM), a parametric model for generating all-sky, few arcminute resolution maps of sky emission at submillimetre to centimetre wavelengths, in both intensity and ...polarisation. Several options are implemented to model the cosmic microwave background, Galactic diffuse emission (synchrotron, free-free, thermal and spinning dust, CO lines), Galactic H ii regions, extragalactic radio sources, dusty galaxies, and thermal and kinetic Sunyaev-Zeldovich signals from clusters of galaxies. Each component is simulated by means of educated interpolations/extrapolations of data sets available at the time of the launch of the Planck mission, complemented by state-of-the-art models of the emission. Distinctive features of the simulations are spatially varying spectral properties of synchrotron and dust; different spectral parameters for each point source; modelling of the clustering properties of extragalactic sources and of the power spectrum of fluctuations in the cosmic infrared background. The PSM enables the production of random realisations of the sky emission, constrained to match observational data within their uncertainties. It is implemented in a software package that is regularly updated with incoming information from observations. The model is expected to serve as a useful tool for optimising planned microwave and sub-millimetre surveys and testing data processing and analysis pipelines. It is, in particular, used to develop and validate data analysis pipelines within the Planck collaboration. A version of the software that can be used for simulating the observations for a variety of experiments is made available on a dedicated website.
Context. The planck satellite will map the full sky at nine frequencies from 30 to 857 GHz. The CMB intensity and polarization that are its prime targets are contaminated by foreground emission. ...Aims. The goal of this paper is to compare proposed methods for separating CMB from foregrounds based on their different spectral and spatial characteristics, and to separate the foregrounds into “components” with different physical origins (Galactic synchrotron, free-free and dust emissions; extra-galactic and far-IR point sources; Sunyaev-Zeldovich effect, etc.). Methods. A component separation challenge has been organised, based on a set of realistically complex simulations of sky emission. Several methods including those based on internal template subtraction, maximum entropy method, parametric method, spatial and harmonic cross correlation methods, and independent component analysis have been tested. Results. Different methods proved to be effective in cleaning the CMB maps of foreground contamination, in reconstructing maps of diffuse Galactic emissions, and in detecting point sources and thermal Sunyaev-Zeldovich signals. The power spectrum of the residuals is, on the largest scales, four orders of magnitude lower than the input Galaxy power spectrum at the foreground minimum. The CMB power spectrum was accurately recovered up to the sixth acoustic peak. The point source detection limit reaches 100 mJy, and about 2300 clusters are detected via the thermal SZ effect on two thirds of the sky. We have found that no single method performs best for all scientific objectives. Conclusions. We foresee that the final component separation pipeline for planck will involve a combination of methods and iterations between processing steps targeted at different objectives such as diffuse component separation, spectral estimation, and compact source extraction.
We present an analysis of the gas kinematics in NGC 2992 based on VLT/MUSE, ALMA, and VLA data. Our aim is to characterise the disc, the wind, and their interplay in the cold molecular and warm ...ionised phases. NGC 2992 is a changing-look Seyfert known to host both a nuclear ultrafast outflow (UFO), and an AGN-driven kiloparsec-scale ionised wind. CO(2−1) and H
α
arise from a multiphase disc with an inclination of 80 deg and radii of 1.5 and 1.8 kpc, respectively. By modelling the gas kinematics, we find that the velocity dispersion of the cold molecular phase,
σ
gas
, is consistent with that of star forming galaxies at the same redshift, except in the inner 600 pc region, and in the region between the cone walls and the disc, where
σ
gas
is a factor of 3−4 larger than in star forming galaxies for both the cold molecular and the warm ionised phases. This suggests that a disc–wind interaction locally boosts the gas turbulence. We detect a clumpy ionised wind in H
β
, O III, H
α
, and N II distributed in two wide-opening-angle ionisation cones reaching scales of 7 kpc (40 arcsec). The O III wind expands with a velocity exceeding −1000 km s
−1
in the inner 600 pc, which is a factor of approximately five greater than the previously reported wind velocity. Based on spatially resolved electron density and ionisation parameter maps, we infer an ionised outflow mass of
M
of, ion
= (3.2 ± 0.3)×10
7
M
⊙
, and a total ionised outflow rate of
Ṁ
of,ion
= 13.5 ± 1
M
⊙
yr
−1
. We detected ten clumps of cold molecular gas located above and below the disc in the ionisation cones, reaching maximum projected distances of 1.7 kpc and showing projected bulk velocities of up to 200 km s
−1
. On these scales, the wind is multiphase, with a fast ionised component and a slower molecular one, and a total mass of
M
of, ion + mol
= 5.8 × 10
7
M
⊙
, of which the molecular component carries the bulk of the mass, namely
M
of, mol
= 4.3 × 10
7
M
⊙
. The dusty molecular outflowing clumps and the turbulent ionised gas are located at the edges of the radio bubbles, suggesting that the bubbles interact with the surrounding medium through shocks, as also supported by the O I/H
α
ratio. Conversely, both the large opening angle and the dynamical timescale of the ionised wind detected in the ionisation cones on 7 kpc scales indicate that this is not related to the radio bubbles but instead likely associated with a previous AGN episode. Finally, we detect a dust reservoir that is co-spatial with the molecular disc, with a cold dust mass of
M
dust
= (4.04 ± 0.03)×10
6
M
⊙
, which is likely responsible for the extended Fe K
α
emission seen on 200 pc scales in hard X-rays and interpreted as reflection by cold dust.
ABSTRACT
As the largest radio telescope in the world, the Square Kilometre Array (SKA) will lead the next generation of radio astronomy. The feats of engineering required to construct the telescope ...array will be matched only by the techniques developed to exploit the rich scientific value of the data. To drive forward the development of efficient and accurate analysis methods, we are designing a series of data challenges that will provide the scientific community with high-quality data sets for testing and evaluating new techniques. In this paper, we present a description and results from the first such Science Data Challenge 1 (SDC1). Based on SKA MID continuum simulated observations and covering three frequencies (560, 1400, and 9200 MHz) at three depths (8, 100, and 1000 h), SDC1 asked participants to apply source detection, characterization, and classification methods to simulated data. The challenge opened in 2018 November, with nine teams submitting results by the deadline of 2019 April. In this work, we analyse the results for eight of those teams, showcasing the variety of approaches that can be successfully used to find, characterize, and classify sources in a deep, crowded field. The results also demonstrate the importance of building domain knowledge and expertise on this kind of analysis to obtain the best performance. As high-resolution observations begin revealing the true complexity of the sky, one of the outstanding challenges emerging from this analysis is the ability to deal with highly resolved and complex sources as effectively as the unresolved source population.
Abstract
We investigate the radio-far infrared (FIR) correlation for a sample of 28 bright high-redshift (1 ≲ z ≲ 4) star-forming galaxies selected in the FIR from the Herschel-ATLAS fields as ...candidates to be strongly gravitationally lensed. The radio information comes either from high sensitivity dedicated ATCA observations at 2.1 GHz or from cross-matches with the FIRST survey at 1.4 GHz. By taking advantage of source brightness possibly enhanced by lensing magnification, we identify a weak evolution with redshift out to z ≲ 4 of the FIR-to-radio luminosity ratio qFIR. We also find that the qFIR parameter as a function of the radio power $L_{1.4\, \rm GHz}$ displays a clear decreasing trend, similarly to what is observed for optically/radio selected lensed quasars found in literature, yet covering a complementary region in the $q_{\rm FIR}-L_{1.4\, \rm GHz}$ diagram. We interpret such a behavior in the framework of an in-situ galaxy formation scenario, as a result of the transition from an early dust-obscured star-forming phase (mainly pinpointed by our FIR selection) to a late radio-loud quasar phase (preferentially sampled by the optical/radio selection).
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