Aims.
Various galaxy classification schemes have been developed so far to constrain the main physical processes regulating evolution of different galaxy types. In the era of a deluge of astrophysical ...information and recent progress in machine learning, a new approach to galaxy classification has become imperative.
Methods.
In this paper, we employ a Fisher Expectation-Maximization (FEM) unsupervised algorithm working in a parameter space of 12 rest-frame magnitudes and spectroscopic redshift. The model (DBk) and the number of classes (12) were established based on the joint analysis of standard statistical criteria and confirmed by the analysis of the galaxy distribution with respect to a number of classes and their properties. This new approach allows us to classify galaxies based on only their redshifts and ultraviolet to near-infrared (UV–NIR) spectral energy distributions.
Results.
The FEM unsupervised algorithm has automatically distinguished 12 classes: 11 classes of VIPERS galaxies and an additional class of broad-line active galactic nuclei (AGNs). After a first broad division into blue, green, and red categories, we obtained a further sub-division into: three red, three green, and five blue galaxy classes. The FEM classes follow the galaxy sequence from the earliest to the latest types, which is reflected in their colours (which are constructed from rest-frame magnitudes used in the classification procedure) but also their morphological, physical, and spectroscopic properties (not included in the classification scheme). We demonstrate that the members of each class share similar physical and spectral properties. In particular, we are able to find three different classes of red passive galaxy populations. Thus, we demonstrate the potential of an unsupervised approach to galaxy classification and we retrieve the complexity of galaxy populations at
z
∼ 0.7, a task that usual, simpler, colour-based approaches cannot fulfil.
The LOFAR LBA Sky Survey de Gasperin, F.; Williams, W. L.; Best, P. ...
Astronomy and astrophysics (Berlin),
04/2021, Letnik:
648
Journal Article
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Context.
The LOw Frequency ARray (LOFAR) is the only radio telescope that is presently capable of high-sensitivity, high-resolution (i.e. < 1 mJy beam
−1
and < 15″) observations at ultra-low ...frequencies (< 100 MHz). To utilise these capabilities, the LOFAR Surveys Key Science Project is undertaking a large survey to cover the entire northern sky with Low Band Antenna (LBA) observations.
Aims.
The LOFAR LBA Sky Survey (LoLSS) aims to cover the entire northern sky with 3170 pointings in the frequency range between 42 − 66 MHz, at a resolution of 15″ and at a sensitivity of 1 mJy beam
−1
(1
σ
). In this work, we outline the survey strategy, the observational status, and the calibration techniques. We also briefly describe several of our scientific motivations and present the preliminary public data release.
Methods.
The preliminary images were produced using a fully automated pipeline aimed at correcting all direction-independent effects in the data. Whilst the direction-dependent effects, such as those from the ionosphere, have not yet been corrected, the images presented in this work are still ten times more sensitive than previous available surveys at these low frequencies.
Results.
The preliminary data release covers 740 deg
2
around the HETDEX spring field region at an angular resolution of 47″ with a median noise level of 5 mJy beam
−1
. The images and the catalogue of 25 247 sources have been publicly released. We demonstrate that the system is capable of reaching a root mean square (rms) noise of 1 mJy beam
−1
and an angular resolution of 15″ once direction-dependent effects are accounted for.
Conclusions.
LoLSS will provide the ultra-low-frequency information for hundreds of thousands of radio sources, providing critical spectral information and producing a unique data set that can be used for a wide range of science topics, such as the search for high redshift galaxies and quasars, the study of the magnetosphere of exoplanets, and the detection of the oldest populations of cosmic-rays in galaxies, clusters of galaxies, as well as those produced by active galactic nuclei.
We describe the construction and general features of VIPERS, the VIMOS Public Extragalactic Redshift Survey. This ESO Large Programme is using the Very Large Telescope with the aim of building a ...spectroscopic sample of ~100 000 galaxies with isubAB< 22.5 and 0.5 <z< 1.5. The survey covers a total area of ~24 degsup 2 within the C FHTLS-Wide W1 and W4 fields. Here we present the survey design, the selection of the source catalogue and the development of the spectroscopic observations. We discuss in detail the overall selection function that results from the combination of the different constituents of the project. Benefiting from the combination of size and detailed sampling of this dataset, we conclude by presenting a map showing in unprecedented detail the large-scale distribution of galaxies between 5 and 8 billion years.
We present the general real- and redshift-space clustering properties of galaxies as measured in the first data release of the VIPERS survey. VIPERS is a large redshift survey designed to probe in ...detail the distant Universe and its large-scale structure at 0.5 < z < 1.2. We describe in this analysis the global properties of the sample and discuss the survey completeness and associated corrections. This sample allows us to measure the galaxy clustering with an unprecedented accuracy at these redshifts. From the redshift-space distortions observed in the galaxy clustering pattern we provide a first measurement of the growth rate of structure at z = 0.8: fsigma8 = 0.47 + or - 0.08. This is completely consistent with the predictions of standard cosmological models based on Einstein gravity, although this measurement alone does not discriminate between different gravity models.
Aims. We trace the evolution and the star formation history of passive red galaxies, using a subset of the VIMOS Public Extragalactic Redshift Survey (VIPERS). The detailed spectral analysis of ...stellar populations of intermediate-redshift passive red galaxies allows the build up of their stellar content to be followed over the last 8 billion years. Methods. We extracted a sample of passive red galaxies in the redshift range 0.4 <z< 1.0 and stellar mass range 10 < log(M sub(star)/M sub(middot in circle)) < 12 from the VIPERS survey. The sample was selected using an evolving cut in the rest-frame U?V color distribution and additional cuts that ensured high quality. The spectra of passive red galaxies were stacked in narrow bins of stellar mass and redshift. We use the stacked spectra to measure the 4000 A break (D 4000) and the H delta Lick index (H delta sub(A)) with high precision. These spectral features are used as indicators of the star formation history of passive red galaxies. We compare the results with a grid of synthetic spectra to constrain the star formation epochs of these galaxies. We characterize the formation redshift-stellar mass relation for intermediate-redshift passive red galaxies. Results. We find that at z~ 1 stellar populations in low-mass passive red galaxies are younger than in high-mass passive red galaxies, similar to what is observed at the present epoch. Over the full analyzed redshift range 0.4 < z< 1.0 and stellar mass range 10 < log(M sub(star)/M sub(middot in circle)) < 12, the D 4000 index increases with redshift, while H delta sub(A) gets lower. This implies that the stellar populations are getting older with increasing stellar mass. Comparison to the spectra of passive red galaxies in the SDSS survey (z~ 0.2) shows that the shape of the relations of D 4000 and H delta sub(A) with stellar mass has not changed significantly with redshift. Assuming a single burst formation, this implies that high-mass passive red galaxies formed their stars at z sub(form)~ 1.7, while low-mass galaxies formed their main stellar populations more recently, at z sub(form)~ 1. The consistency of these results, which were obtained using two independent estimators of the formation redshift (D 4000 and H delta sub(A)), further strengthens a scenario in which star formation proceeds from higher to lower mass systems as time passes, i.e., what has become known as the downsizing picture.
We present the first Public Data Release (PDR-1) of the VIMOS Public Extragalactic Survey (VIPERS). It comprises 57 204 spectroscopic measurements together with all additional information necessary ...for optimal scientific exploitation of the data, in particular the associated photometric measurements and quantification of the photometric and survey completeness. VIPERS is an ESO Large Programme designed to build a spectroscopic sample of similar to 100 000 galaxies with i sub(AB) < 22.5 and 0.5 < z < 1.2 with high sampling rate ( similar to 45%). The survey spectroscopic targets are selected from the CFHTLS-Wide five-band catalogues in the W1 and W4 fields. The final survey will cover a total area of nearly 24 deg super(2), for a total comoving volume between z = 0.5 and 1.2 of similar to 4 x 10 super(7) h super(-3) Mpc super(3) and a median galaxy redshift of z similar to 0.8. The release presented in this paper includes data from virtually the entire W4 field and nearly half of the W1 area, thus representing 64% of the final dataset. We provide a detailed description of sample selection, observations and data reduction procedures; we summarise the global properties of the spectroscopic catalogue and explain the associated data products and their use, and provide all the details for accessing the data through the survey database (http://vipers.inaf.it) where all information can be queried interactively.
The Type II AGN-host galaxy connection Vietri, G.; Garilli, B.; Polletta, M. ...
Astronomy and astrophysics (Berlin),
03/2022, Letnik:
659
Journal Article
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We present a study of optically selected Type II active galactic nuclei (AGN) at 0.5 <
z
< 0.9 from the VIPERS and VVDS surveys, to investigate the connection between AGN activity and the physical ...properties of their host galaxies. The host stellar mass is estimated through spectral energy distribution fitting with the CIGALE code, and star formation rates are derived from the OII
λ
3727 Å line luminosity. We find that 49% of the AGN host galaxies are on or above the main sequence (MS), 40% lie in the sub-MS locus, and 11% in the quiescent locus. Using the OIII
λ
5007 Å line luminosity as a proxy of the AGN power, we find that at fixed AGN power Type II AGN host galaxies show a bimodal behaviour: systems with host galaxy stellar mass < 10
10
M
⊙
reside along the MS or in the starbursts locus (high-SF Type II AGN), while systems residing in massive host galaxies (> 10
10
M
⊙
) show a lower level of star formation (low-SF Type II AGN). At all stellar masses the offset from the MS is positively correlated with the AGN power. We interpret this correlation as evidence of co-evolution between the AGN and the host, possibly due to the availability of cold gas. In the most powerful AGN with host galaxies below the MS we find a hint, though weak, of asymmetry in the OIII line profile, likely due to outflowing gas, consistent with a scenario in which AGN feedback removes the available gas and halts the star formation in the most massive hosts.
Aims. The aim of this work is to characterize physical properties of ultra luminous infrared galaxies (ULIRGs) and luminous infrared galaxies (LIRGs) detected in the far-infrared (FIR) 90 μm band in ...the AKARI Deep Field-South (ADF-S) survey. In particular, we want to estimate the active galactic nucleus (AGN) contribution to the LIRGs and ULIRGs’ infrared emission and which types of AGNs are related to their activity. Methods. We examined 69 galaxies at redshift ≥0.05 detected at 90 μm by the AKARI satellite in the ADF-S, with optical counterparts and spectral coverage from the ultraviolet to the FIR. We used two independent spectral energy distribution fitting codes: one fitting the SED from FIR to FUV (CIGALE) (we use the results from CIGALE as a reference) and gray-body + power spectrum fit for the infrared part of the spectra (CMCIRSED) in order to identify a subsample of ULIRGs and LIRGs, and to estimate their properties. Results. Based on the CIGALE SED fitting, we have found that LIRGs and ULIRGs selected at the 90 μm AKARI band compose ~56% of our sample (we found 17 ULIRGs and 22 LIRGs, spanning over the redshift range 0.06 <z< 1.23). Their physical parameters, such as stellar mass, star formation rate (SFR), and specific SFR are consistent with the ones found for other samples selected at infrared wavelengths. We have detected a significant AGN contribution to the mid-infrared luminosity for 63% of LIRGs and ULIRGs. Our LIRGs contain Type 1, Type 2, and intermediate types of AGN, whereas for ULIRGs, a majority (more than 50%) of AGN emission originates from Type 2 AGNs. The temperature-luminosity and temperature-mass relations for the dust component of ADF–S LIRGs and ULIRGs indicate that these relations are shaped by the dust mass and not by the increased dust heating. Conclusions. We conclude that LIRGs contain Type 1, Type 2, and intermediate types of AGNs, with an AGN contribution to the mid infrared emission at the median level of 13 ± 3%, whereas the majority of ULIRGs contain Type 2 AGNs, with a median AGN fraction equal to 19 ± 8%.
Although it is now recognized that low surface brightness galaxies (LSBs) constitute a large fraction of the number density of galaxies, many of their properties are still poorly known. Based on only ...a few studies, LSBs are often considered to be “dust poor”, that is, with a very low amount of dust. For the first time, we use a large sample of LSBs and high surface brightness galaxies (HSBs) with deep observational data to study the variation of stellar and dust properties as a function of the surface brightness-surface mass density. Our sample consists of 1631 galaxies that were optically selected (with
ugrizy
-bands) at
z
< 0.1 from the North Ecliptic Pole (NEP) Wide field. We used the large multiwavelength set of ancillary data in this field ranging from UV to the far-infrared wavelengths. We measured the optical size and the surface brightness of the targets and analyzed their spectral energy distribution using the
CIGALE
fitting code. Based on the average
r
-band surface brightness (
μ̄
e
), our sample consists of 1003 LSBs (
μ̄
e
> 23 mag arcsec
−2
) and 628 HSBs (
μ̄
e
≤ 23 mag arcsec
−2
). We found that the specific star formation rate and specific infrared luminosity (total infrared luminosity per stellar mass) remain mostly flat as a function of surface brightness for both LSBs and HSBs that are star forming, but these characteristics decline steeply when the LSBs and HSBs are quiescent galaxies. The majority of LSBs in our sample have negligible dust attenuation (< 0.1 mag), and only about 4% of them show significant attenuation, with a mean
V
-band attenuation of 0.8 mag. We found that the LSBs with a significant attenuation also have a high
r
-band mass-to-light ratio (M/L
r
> 3
M
⊙
/
L
⊙
), making them outliers from the linear relation of surface brightness and stellar mass surface density. These outlier LSBs also show similarity to the extreme giant LSBs from the literature, indicating a possibly higher dust attenuation in giant LSBs. This work provides a large catalog of LSBs and HSBs as well as detailed measurements of several optical and infrared physical properties. Our results suggest that the dust content of LSBs is more varied than previously thought, with some of them having significant attenuation that makes them fainter than their intrinsic value. With these results, we will be able to make predictions on the dust content of the population of LSBs and how the presence of dust will affect their observations from current and upcoming surveys like JWST and LSST.
In pursuit of giants Donevski, D; Lapi, A; Małek, K ...
Astronomy and astrophysics (Berlin),
12/2020, Letnik:
644
Journal Article
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The dust-to-stellar mass ratio (Mdust/M⋆) is a crucial, albeit poorly constrained, parameter for improving our understanding of the complex physical processes involved in the production of dust, ...metals, and stars in galaxy evolution. In this work, we explore trends of Mdust/M⋆ with different physical parameters and using observations of 300 massive dusty star-forming galaxies detected with ALMA up to z ≈ 5. Additionally, we interpret our findings with different models of dusty galaxy formation. We find that Mdust/M⋆ evolves with redshift, stellar mass, specific star formation rates, and integrated dust size, but that evolution is different for main-sequence galaxies than it is for starburst galaxies. In both galaxy populations, Mdust/M⋆ increases until z ∼ 2, followed by a roughly flat trend towards higher redshifts, suggesting efficient dust growth in the distant universe. We confirm that the inverse relation between Mdust/M⋆ and M⋆ holds up to z ≈ 5 and can be interpreted as an evolutionary transition from early to late starburst phases. We demonstrate that the Mdust/M⋆ in starbursts reflects the increase in molecular gas fraction with redshift and attains the highest values for sources with the most compact dusty star formation. State-of-the-art cosmological simulations that include self-consistent dust growth have the capacity to broadly reproduce the evolution of Mdust/M⋆ in main-sequence galaxies, but underestimating it in starbursts. The latter is found to be linked to lower gas-phase metallicities and longer dust-growth timescales relative to observations. The results of phenomenological models based on the main-sequence and starburst dichotomy as well as analytical models that include recipes for rapid metal enrichment are consistent with our observations. Therefore, our results strongly suggest that high Mdust/M⋆ is due to rapid dust grain growth in the metal-enriched interstellar medium. This work highlights the multi-fold benefits of using Mdust/M⋆ as a diagnostic tool for: (1) disentangling main-sequence and starburst galaxies up to z ∼ 5; (2) probing the evolutionary phase of massive objects; and (3) refining the treatment of the dust life cycle in simulations.
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