Context. Deep far-infrared (FIR) cosmological surveys are known to be affected by source confusion, causing issues when examining the main sequence (MS) of star forming galaxies. In the past this has ...typically been partially tackled by the use of stacking. However, stacking only provides the average properties of the objects in the stack. Aims. This work aims to trace the MS over 0.2 ≤ z < 6.0 using the latest de-blended Herschel photometry, which reaches ≈10 times deeper than the 5σ confusion limit in SPIRE. This provides more reliable star formation rates (SFRs), especially for the fainter galaxies, and hence a more reliable MS. Methods. We built a pipeline that uses the spectral energy distribution (SED) modelling and fitting tool CIGALE to generate flux density priors in the Herschel SPIRE bands. These priors were then fed into the de-blending tool XID+ to extract flux densities from the SPIRE maps. In the final step, multi-wavelength data were combined with the extracted SPIRE flux densities to constrain SEDs and provide stellar mass (M⋆) and SFRs. These M⋆ and SFRs were then used to populate the SFR-M⋆ plane over 0.2 ≤ z < 6.0. Results. No significant evidence of a high-mass turn-over was found; the best fit is thus a simple two-parameter power law of the form log(SFR) = αlog(M⋆) − 10.5 + β. The normalisation of the power law increases with redshift, rapidly at z ≲ 1.8, from 0.58 ± 0.09 at z ≈ 0.37 to 1.31 ± 0.08 at z ≈ 1.8. The slope is also found to increase with redshift, perhaps with an excess around 1.8 ≤ z < 2.9. Conclusions. The increasing slope indicates that galaxies become more self-similar as redshift increases. This implies that the specific SFR of high-mass galaxies increases with redshift, from 0.2 to 6.0, becoming closer to that of low-mass galaxies. The excess in the slope at 1.8 ≤ z < 2.9, if present, coincides with the peak of the cosmic star formation history.
HELP: the Herschel Extragalactic Legacy Project Shirley, R; Duncan, K; Campos Varillas, M C ...
Monthly notices of the Royal Astronomical Society,
10/2021, Letnik:
507, Številka:
1
Journal Article
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ABSTRACT
We present the Herschel Extragalactic Legacy Project (HELP). This project collates, curates, homogenizes, and creates derived data products for most of the premium multiwavelength ...extragalactic data sets. The sky boundaries for the first data release cover 1270 deg2 defined by the Herschel SPIRE extragalactic survey fields; notably the Herschel Multi-tiered Extragalactic Survey (HerMES) and the Herschel Atlas survey (H-ATLAS). Here, we describe the motivation and principal elements in the design of the project. Guiding principles are transparent or ‘open’ methodologies with care for reproducibility and identification of provenance. A key element of the design focuses around the homogenization of calibration, meta data, and the provision of information required to define the selection of the data for statistical analysis. We apply probabilistic methods that extract information directly from the images at long wavelengths, exploiting the prior information available at shorter wavelengths and providing full posterior distributions rather than maximum-likelihood estimates and associated uncertainties as in traditional catalogues. With this project definition paper, we provide full access to the first data release of HELP; Data Release 1 (DR1), including a monolithic map of the largest SPIRE extragalactic field at 385 deg2 and 18 million measurements of PACS and SPIRE fluxes. We also provide tools to access and analyse the full HELP data base. This new data set includes far-infrared photometry, photometric redshifts, and derived physical properties estimated from modelling the spectral energy distributions over the full HELP sky. All the software and data presented is publicly available.
Context. Over the past few years the Atacama Large Millimeter Array (ALMA) has detected dust-rich galaxies whose cold dust emission is spatially disconnected from the ultraviolet (UV) rest-frame ...emission. This represents a challenge for modeling their spectral energy distributions (SED) with codes based on an energy budget between the stellar and dust components. This could potentially weaken the solidity of the physical parameters measured with these modeling tools. Aims. We want to verify the validity of energy balance modeling on a sample of galaxies observed from the UV to the sub-millimeter rest frame with ALMA and decipher what information can be reliably retrieved from the analysis of the full SED and from subsets of wavelengths. Methods. We select 17 sources at z ≃ 2 in the Hubble Ultra-Deep Field (HUDF) and in the GOODS-South field detected with ALMA and Herschel and for which UV to near-infrared rest-frame ancillary data are available. We fit the data with CIGALE exploring different configurations for dust attenuation and star formation histories, considering either the full dataset or one that is reduced to the stellar and dust emission. We compare estimates of the dust luminosities, star formation rates, and stellar masses. Results. The fit of the stellar continuum alone with the starburst attenuation law can only reproduce up to 50% of the total dust luminosity observed by Herschel and ALMA. This deficit is found to be marginally consistent with similar quantities estimated in the COSMOS field and is found to increase with the specific star formation rate. The combined stellar and dust SEDs are well fitted when different attenuation laws are introduced. Shallow attenuation curves are needed for the galaxies whose cold dust distribution is very compact compared to starlight. The stellar mass estimates are affected by the choice of the attenuation law. The star formation rates are robustly estimated as long as dust luminosities are available. The large majority of the galaxies are above the average main sequence of star forming galaxies and one source is a strong starburst.
Context. Dust attenuation shapes the spectral energy distribution of galaxies. It is particularly true for dusty galaxies in which stars experience a heavy attenuation. The combination of UV to IR ...photometry with the spectroscopic measurement of the Hα recombination line helps to quantify dust attenuation of the whole stellar population and its wavelength dependence. Aims. We want to derive the shape of the global attenuation curve and the amount of obscuration affecting young stars or nebular emission and the bulk of the stellar emission in a representative sample of galaxies selected in IR. We will compare our results to the commonly used recipes of Calzetti et al. and Charlot and Fall, and to predictions of radiative transfer models. Methods. We selected an IR complete sample of galaxies in the COSMOS 3D-HST CANDELS field detected with the Herschel satellite with a signal to noise ratio larger than five. Optical to NIR photometry is available as well as NIR spectroscopy for each source. We reduced the sample to the redshift range 0.6 < z < 1.6 to include the Hα line in the G141 grism spectra. We have used a new version of the CIGALE code to fit simultaneously the continuum and Hα line emission of the 34 selected galaxies. Results. Using flexible attenuation laws with free parameters, we are able to measure the shape of the attenuation curve for each galaxy as well as the amount of attenuation of each stellar population, the former being in general steeper than the starburst law in the UV-optical with a large variation of the slope among galaxies. The attenuation of young stars or nebular continuum is found on average about twice the attenuation affecting older stars, again with a large variation. Our model with power-laws, based on a modification of the Charlot and Fall recipe, gives results in better agreement with the radiative transfer models than the global modification of the slope of the Calzetti law.
Aims. The Herschel Extragalactic Legacy Project (HELP) focuses on the data from ESA’s Herschel mission, which covered over 1300 deg2 and is preparing to publish a multi-wavelength catalogue of ...millions of objects. Our main goal is to find the best approach to simultaneously fitting spectral energy distributions (SEDs) of millions of galaxies across a wide redshift range to obtain homogeneous estimates of the main physical parameters of detected infrared (IR) galaxies. Methods. We perform SED fitting on the ultraviolet(UV)/near-infrared(NIR) to far-infrared(FIR) emission of 42 047 galaxies from the pilot HELP field: ELAIS N1. To do this we use the latest release of CIGALE, a galaxy SED fitting code relying on energy balance, to deliver the main physical parameters such as stellar mass, star formation rate, and dust luminosity. We implement additional quality criteria to the fits by calculating χ2 values for the stellar and dust part of the spectra independently. These criteria allow us to identify the best fits and to identify peculiar galaxies. We perform the SED fitting of ELAIS N1 galaxies by assuming three different dust attenuation laws separately allowing us to test the impact of the assumed law on estimated physical parameters. Results. We implemented two additional quality value checks for the SED fitting method based on stellar mass estimation and energy budget. This method allows us to identify possible objects with incorrect matching in the catalogue and peculiar galaxies; we found 351 possible candidates of lensed galaxies using two complementary χ2s criteria (stellar and infrared χ2s) and photometric redshifts calculated for the IR part of the spectrum only. We find that the attenuation law has an important impact on the stellar mass estimate (on average leading to disparities of a factor of two). We derive the relation between stellar mass estimates obtained by three different attenuation laws and we find the best recipe for our sample. We also make independent estimates of the total dust luminosity parameter from stellar emission by fitting the galaxies with and without IR data separately.
ABSTRACT
Source classifications, stellar masses, and star-formation rates are presented for ≈80 000 radio sources from the first data release of the Low Frequency Array Two-metre Sky Survey (LoTSS) ...Deep Fields, which represents the widest deep radio survey ever undertaken. Using deep multi-wavelength data spanning from the ultraviolet to the far-infrared, spectral energy distribution (SED) fitting is carried out for all of the LoTSS Deep host galaxies using four different SED codes, two of which include modelling of the contributions from an active galactic nucleus (AGN). Comparing the results of the four codes, galaxies that host a radiative AGN are identified, and an optimized consensus estimate of the stellar mass and star-formation rate for each galaxy is derived. Those galaxies with an excess of radio emission over that expected from star formation are then identified, and the LoTSS Deep sources are divided into four classes: star-forming galaxies, radio-quiet AGN, and radio-loud high-excitation and low-excitation AGN. Ninety-five per cent of the sources can be reliably classified, of which more than two-thirds are star-forming galaxies, ranging from normal galaxies in the nearby Universe to highly-starbursting systems at z > 4. Star-forming galaxies become the dominant population below 150-MHz flux densities of ≈1 mJy, accounting for 90 per cent of sources at S150MHz ∼ 100 μJy. Radio-quiet AGN comprise ≈10 per cent of the overall population. Results are compared against the predictions of the SKADS and T-RECS radio sky simulations, and improvements to the simulations are suggested.
Context.
Low-surface-brightness galaxies (LSBGs), which are defined as galaxies that are fainter than the night sky, play a crucial role in our understanding of galaxy evolution and in cosmological ...models. Upcoming large-scale surveys, such as
Rubin
Observatory Legacy Survey of Space and Time and
Euclid
, are expected to observe billions of astronomical objects. In this context, using semiautomatic methods to identify LSBGs would be a highly challenging and time-consuming process, and automated or machine learning-based methods are needed to overcome this challenge.
Aims.
We study the use of transformer models in separating LSBGs from artefacts in the data from the Dark Energy Survey (DES) Data Release 1. Using the transformer models, we then search for new LSBGs from the DES that the previous searches may have missed. Properties of the newly found LSBGs are investigated, along with an analysis of the properties of the total LSBG sample in DES.
Methods.
We created eight different transformer models and used an ensemble of these eight models to identify LSBGs. This was followed by a single-component Sérsic model fit and a final visual inspection to filter out false positives.
Results.
Transformer models achieved an accuracy of ~94% in separating the LSBGs from artefacts. In addition, we identified 4083 new LSBGs in DES, adding an additional ~17% to the LSBGs already known in DES. This also increased the number density of LSBGs in DES to 5.5 deg
−2
. The new LSBG sample consists of mainly blue and compact galaxies. We performed a clustering analysis of the LSBGs in DES using an angular two-point auto-correlation function and found that LSBGs cluster more strongly than their high-surface-brightness counterparts. This effect is driven by the red LSBG. We associated 1310 LSBGs with galaxy clusters and identified 317 ultradiffuse galaxies among them. We found that these cluster LSBGs are getting bluer and larger in size towards the edge of the clusters when compared with those in the centre.
Conclusions.
Transformer models have the potential to be equivalent to convolutional neural networks as state-of-the-art algorithms in analysing astronomical data. The significant number of LSBGs identified from the same dataset using a different algorithm highlights the substantial impact of our methodology on our capacity to discover LSBGs. The reported number density of LSBGs is only a lower estimate and can be expected to increase with the advent of surveys with better image quality and more advanced methodologies.
ABSTRACT
Red ultra-compact massive galaxies, called red nuggets were formed at high redshifts (z ∼ 2–3). Survivors of red nuggets, known as relics, observed at lower redshifts (z < 2) are believed to ...remain almost unchanged since their formation. For the first time, we verify the environmental properties of red nuggets at intermediate redshift (0.5 < z < 0.9) using 42 red, massive (log(Mstar/M⊙) ≥ 10.9), and ultra compact (Re < 1.5 kpc) from the VIMOS Public Extragalactic Redshift Survey (VIPERS). We found that the increasing fraction of red galaxies, when moving to denser environments, is driven by the red massive normal-size galaxies. Red nuggets, similarly to red intermediate-mass (10.4 ≲ log (Mstar/M⊙) < 10.9) ultra-compact galaxies, are found in various types of environments, with consistent (within 1σ) fractions across all local densities. Analysis of red nugget stellar ages suggests that relics are preferably found in high-density regions while quiescent red nuggets are overabundant in low-density environments. We speculate that red nuggets have survived to lower redshifts via two channels: i) in low-density environments, where the fraction of red nuggets decreases as time passes due to (very) limited merger activity, ii) in high-density environments, where the number of red nuggets drops at higher redshift due to merger activity and is preserved at lower redshift as the high velocities of clusters prevent them from being cannibalized. Even more, the fraction of red nuggets in clusters may increase due to the addition of red massive normal-size galaxies deprived of their envelopes with cosmic time.
Context.
Hyperluminous infrared galaxies (HLIRGs) are shown to have been more abundant in early epochs. The small samples used in earlier studies are not sufficient to draw robust statistical ...conclusions regarding the physical properties and the power sources of these extreme infrared (IR) bright galaxies.
Aims.
We make use of multi-wavelength data of a large HLIRG sample to derive the main physical properties, such as stellar mass, star formation rate (SFR), volume density, and the contribution to the cosmic stellar mass density and the cosmic SFR density. We also study the black hole (BH) growth rate and its relationship with the SFR of the host galaxy.
Methods.
We selected 526 HLIRGs in three deep fields (Boötes, Lockman-Hole, and ELAIS-N1) and adopted two spectral energy distribution (SED) fitting codes: CIGALE, which assumes energy balance, and CYGNUS, which is based on radiative transfer models and does not adopt an energy balance principle. We used two different active galactic nucleus (AGN) models in CIGALE and three AGN models in CYGNUS to compare results that were estimated using different SED fitting codes and a range of AGN models.
Results.
The stellar mass, total IR luminosity, and AGN luminosity agree well among different models, with a typical median offset of 0.1 dex. The SFR estimates show the largest dispersions (up to 0.5 dex). This dispersion has an impact on the subsequent analysis, which may suggest that the previous contradictory results could partly have been due to the different choices in methods. HLIRGs are ultra-massive galaxies, with 99% of them having stellar masses larger than 10
11
M
⊙
. Our results reveal a higher space density of ultra-massive galaxies than what was found by previous surveys or predicted via simulations. We find that HLIRGs contribute more to the cosmic SFR density as redshift increases. In terms of BH growth, the two SED fitting methods provide different results. We can see a clear trend in whereby SFR decreases as AGN luminosity increases when using CYGNUS estimates. This may possibly imply quenching by AGN in this case, whereas this trend is much weaker when using CIGALE estimates. This difference is also influenced by the dispersion between SFR estimates obtained by the two codes.
Context.
Our knowledge of galaxy metallicity – the result of the integrated star formation history and the evolution of the interstellar medium – is important for constraining the description of ...galaxy evolution. As such, it has been widely studied in the local Universe, in particular, using data from the Sloan Digital Sky Survey (SDSS). The VIMOS Public Extragalactic Redshift Survey (VIPERS) allows us to extend such studies up to redshift of
z
∼ 0.7 and to quantify a possible evolution of the galaxy metallicity with high statistical precision.
Aims.
We focus on how to homogenize the comparison between galaxy samples having different characteristics. We check the projections of the fundamental metallicity relation (FMR) and the evolution of these projections between a sample selected at
z
∼ 0 (SDSS) and
z
∼ 0.7 (VIPERS). We check, in particular, whether and to what extent selection criteria can affect the results.
Methods.
We checked the influence of different biases introduced either by physical constraints (evolution of the luminosity function and differences in the fraction of blue galaxies) or data selection (the signal-to-noise ratio and quality of the spectra) on the FMR and its projections. To separate the differences occurring due to the physical evolution of galaxies with redshift from the false evolution mimed by these biases, we first analyzed the effects of these biases individually on the SDSS sample, and next, starting from the SDSS data, we built a VIPERS-equivalent
z
∼ 0 sample, replicating the main characteristics of VIPERS sample at
z
∼ 0.7 for a fair comparison.
Results.
We found that the FMR projections are all sensitive to biases introduced by the selection on S/N and the quality flags of the emission line measurements in the spectra, especially the O
III
λ
4959 line. The exception is the metallicity versus the sSFR plane which is insensitive to these biases. The evolution of the luminosity function introduces a bias only in the plane metallicity versus the star formation rate (SFR) while the fraction of blue galaxies has no impact on results.
Conclusions.
With the applied methodology, the median metallicities estimated in each stellar mass-SFR bin of the samples at
z
∼ 0 and
z
∼ 0.7 agree within the uncertainties between SDSS and VIPERS samples (Δ log(O/H) ∼ 0.6⟨
s
VIPERS
⟩ = 0.08 dex, where
s
VIPERS
stands for the metallicity standard deviation, without taking into account the biases). This difference can be reduced to ∼0.4⟨
s
VIPERS
⟩ = 0.06 dex taking into account the biases, in particular the evolution of the luminosity function. We find a shift of the FMR projections towards lower metallicity which can be mimicked by a conservative selection on the S/N of emission lines. We also find either an overselection of high-metal galaxies at low stellar mass or an overestimation of the metallicity for the same sources at
z
∼ 0.7. Any bias taken into account in this study cannot mimic this overselection or overestimation at low redshift.
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