Aims. Photometric data of galaxies covering the rest-frame wavelength range from far-UV to far-IR make it possible to derive galaxy properties with a high reliability by fitting the attenuated ...stellar emission and the related dust emission at the same time. Methods. For this purpose we wrote the code CIGALE (Code Investigating GALaxy Emission) that uses model spectra composed of the Maraston (or PEGASE) stellar population models, synthetic attenuation functions based on a modified Calzetti law, spectral line templates, the Dale & Helou dust emission models, and optional spectral templates of obscured AGN. Depending on the input redshifts, filter fluxes were computed for the model set and compared to the galaxy photometry by carrying out a Bayesian-like analysis. CIGALE was tested by analysing 39 nearby galaxies selected from SINGS. The reliability of the different model parameters was evaluated by studying the resulting expectation values and their standard deviations in relation to the input model grid. Moreover, the influence of the filter set and the quality of photometric data on the code results was estimated. Results. For up to 17 filters with effective wavelengths between 0.15 and 160 μm, we find robust results for the mass, star formation rate, effective age of the stellar population at 4000 Å, bolometric luminosity, luminosity absorbed by dust, and attenuation in the far-UV. Details of the star formation history (excepting the burst fraction) and the shape of the attenuation curve are difficult to investigate with the available broad-band UV and optical photometric data. A study of the mutual relations between the reliable properties confirms the dependence of star formation activity on morphology in the local Universe and indicates a significant drop in this activity at about 1011 $M_{\odot}$ towards higher total stellar masses. The dustiest galaxies in the SINGS sample are present in the same mass range. On the other hand, the far-UV attenuation of our sample galaxies does not appear to show a significant dependence on star formation activity. Conclusions. The results for our SINGS test sample demonstrate that CIGALE can be a valuable tool for studying basic properties of galaxies in the near and distant Universe if UV-to-IR data are available.
We show that measures of star formation rates (SFRs) for infrared galaxies using either single-band 24 is a subset of m or extinction-corrected Pa alpha luminosities are consistent in the total ...infrared luminosity = L(TIR) ~ 1010 L range. MIPS 24 is a subset of m photometry can yield SFRs accurately from this luminosity upward: SFR(M yr-1) = 7.8 X 10-10 L(24 is a subset of m, L ) from L(TIR) = 5X 109 L to 1011 L and SFR = 7.8 X 10-10 L(24 is a subset of m, L )(7.76 X 10-11 L(24))0.048 for higher L(TIR). For galaxies with L(TIR) >= 1010 L , these new expressions should provide SFRs to within 0.2 dex. For L(TIR) >= 1011 L , we find that the SFR of infrared galaxies is significantly underestimated using extinction-corrected Pa alpha (and presumably using any other optical or near-infrared recombination lines). As a part of this work, we constructed spectral energy distribution templates for eleven luminous and ultraluminous purely star forming infrared galaxies and over the spectral range 0.4 is a subset of m to 30 cm. We use these templates and the SINGS data to construct average templates from 5 is a subset of m to 30 cm for infrared galaxies with L(TIR) = 5X 109 to 1013 L . All of these templates are made available online.
We present Spitzer IRS mid-infrared spectra for 15 gravitationally lensed, 24 mum-selected galaxies, and combine the results with four additional very faint galaxies with IRS spectra in the ...literature. The median intrinsic 24 mum flux density of the sample is 130 muJy, enabling a systematic survey of the spectral properties of the very faint 24 mum sources that dominate the number counts of Spitzer cosmological surveys. Six of the 19 galaxy spectra (32%) show the strong mid-IR continuua expected of AGNs; X-ray detections confirm the presence of AGNs in three of these cases, and reveal AGNs in two other galaxies. These results suggest that nuclear accretion may contribute more flux to faint 24 mum-selected samples than previously assumed. Almost all the spectra show some aromatic (PAH) emission features; the measured aromatic flux ratios do not show evolution from image. In particular, the high signal-to-noise mid-IR spectrum of SMM J163554.2+661225 agrees remarkably well with low-redshift, lower luminosity templates. We compare the rest-frame 8 mum and total infrared luminosities of star-forming galaxies, and find that the behavior of this ratio with total IR luminosity has evolved modestly from image to image. Since the high aromatic-to-continuum flux ratios in these galaxies rule out a dominant contribution by AGNs, this finding implies systematic evolution in the structure and/or metallicity of infrared sources with redshift. It also has implications for the estimates of star-forming rates inferred from 24 mum measurements, in the sense that at image, a given observed frame 24 mum luminosity corresponds to a lower bolometric luminosity than would be inferred from low-redshift templates of similar luminosity at the corresponding rest wavelength.
We have observed the cluster RX J0152.7-1357 (z 6 0.83) at 24 km with the Multiband Imaging Photometer for Spitzer (MIPS). We detected 22 sources associated with spectroscopically confirmed cluster ...members, while 10 more have photometric redshifts compatible with membership. Two of the 32 likely cluster members contain obvious active nuclei, while the others are associated with dusty star formation. The median IR-determined star formation rate among the remaining galaxies is estimated at 22 M sub( )yr super(-1), significantly higher than in previous estimates from optical data. Most of the mid-infrared (MIR) emitting galaxies also have optical emission lines, but a few do not and hence have completely hidden bursts of star formation or AGN activity. An excess of MIR-emitting galaxies is seen in the cluster, compared to the field at the same redshift. The MIR cluster members are more associated with previously detected infalling late-type galaxies rather than triggered by the ongoing merging of bigger X-ray clumps. Rough estimates also show that ram pressure may not be capable of stripping the gas away from cluster outskirt galaxies, but it may disturb the gas enough to trigger the star formation activity. Harassment can also play a role if, for example, these galaxies belong to poor galaxy groups. Thus, bursts of star formation occur in the cluster environment and could also help consume the galaxy gas content, in addition to ram pressure, harassment, or galaxy-galaxy strong interactions.
Aims.We constrain the past star formation histories of a sample of 25 distant ($\bar{z}\sim 0.7$) luminous infrared galaxies (LIRGs) detected with the mid infrared cameras ISOCAM and MIPS onboard the ...ISO and Spitzer satellites. Methods.We used high-resolution VLT-FORS2 spectroscopy in addition to a comprehensive library of 200 000 model optical spectra to derive Bayesian likelihood estimates of the star formation histories of these galaxies, based on analysis of Balmer absorption lines and the 4000 Å break. Results. The locus of distant LIRGs in the diagram defined by H$\delta_{\rm A}$ and D4000 is roughly comparable to that of local LIRGs observed with IRAS, suggesting that no trend toward an evolution is detected between the local and distant LIRGs. We obtain similar results when using either the H8 or the H$\delta_{\rm A}$ Balmer absorption-line indices in combination with D4000. By computing a birthrate parameter ($b={\it SFR}/\langle {\it SFR}\rangle$) of $4\pm1$, we confirme that the distant LIRGs are currently experiencing a major phase of star formation. The most likely duration of the bursts is 0.10$^{+0.16}_{-0.06}$ Gyr, during which the LIRGs produce ~5–10% of their current stellar mass. No evidence was found for successive starbursts on the scale of a few times 107 yr, such as those predicted by some numerical simulations of major mergers. However, the high number density of those galaxies suggests that they could have experienced between two and four LIRG phases until the present epoch. This scenario is not consistent with the formation of the $z\sim0.7$ LIRGs through the continuous star formation characterizing isolated spiral galaxies as has been independently argued based on their morphology. Instead, minor mergers, tidal interactions, or gas accretion remain plausible triggering mechanisms for more than half of the distant LIRGs that do not harbor the morphology of major mergers.
Aims. We investigate whether the mean star formation activity of star-forming galaxies from z =0 to z =0.7 in the GOODS-S field can be reproduced by simple evolution models of these systems. In this ...case, such models might be used as first-order references for studies at higher z to decipher when and to what extent a secular evolution is sufficient to explain the star formation history in galaxies. Methods. We selected star- forming galaxies at z =0 and at z =0.7 in IR and in UV to have access to all the recent star formation. We focused on galaxies with a stellar mass ranging between 10 super(10) and 10 6M_{\odot} for which the results are not biased by the selections. We compared the data to chemical evolution models developed for spiral galaxies and originally built to reproduce the main characteristics of the Milky Way and nearby spirals without fine-tuning them for the present analysis. Results. We find a shallow decrease in the specific star formation rate (SSFR) when the stellar mass increases. The evolution of the SSFR characterizing both UV and IR selected galaxies from z =0 to z =0.7 is consistent with the models built to reproduce the present spiral galaxies. There is no need to strongly modify of the physical conditions in galaxies to explain the average evolution of their star formation from z =0 to z =0.7. We use the models to predict the evolution of the star formation rate and the metallicity on a wider range of redshift and we compare these predictions with the results of semi-analytical models.
We present evidence that the mid infrared (MIR, rest frame 5–30 μm) is a good tracer of the total infrared luminosity, L(IR)(=$L8{-}1000~\mu{\rm m}$), and star formation rate (SFR), of galaxies up to ...$z\sim$ 1.3. We use deep MIR images from the Infrared Space Observatory (ISO) and the Spitzer Space Telescope in the Northern field of the Great Observatories Origins Deep Survey (GOODS-N) together with VLA radio data to compute three independant estimates of L(IR). The L(IR, MIR) derived from the observed 15 and/or 24 μm flux densities using a library of template SEDs, and L(IR, radio), derived from the radio (1.4 and/or 8.5 GHz) using the radio-far infrared correlation, agree with a 1-σ dispersion of 40%. We use the k-correction as a tool to probe different parts of the MIR spectral energy distribution (SED) of galaxies as a function of their redshift and find that on average distant galaxies present MIR SEDs very similar to local ones. However, in the redshift range $z=$ 0.4–1.2, L(IR, 24 μm) is in better agreement with L(IR, radio) than L(IR, 15 μm) by 20%, suggesting that the warm dust continuum is a better tracer of the SFR than the broad emission features due to polycyclic aromatic hydrocarbons (PAHs). We find marginal evidence for an evolution with redshift of the MIR SEDs: two thirds of the distant galaxies exhibit rest-frame MIR colors (L(12 μm)/L(7 μm) and L(10 μm)/L(15 μm) luminosity ratios) below the median value measured for local galaxies. Possible explanations are examined but these results are not sufficient to constrain the physics of the emitting regions. If confirmed through direct spectroscopy and if it gets amplified at higher redshifts, such an effect should be considered when deriving cosmic star formation histories of dust-obscured galaxies. We compare three commonly used SED libraries which reproduce the color-luminosity correlations of local galaxies with our data and discuss possible refinements to the relative intensities of PAHs, warm dust continuum and silicate absorption.
One hundred and five 15 mu m-selected objects in three ISO (Infrared Space Observatory) deep survey fields (CFRS 3 super(h), UDSR and UDSF) are studied on the basis of their high-quality optical ...spectra with resolution R > 1000 from VLT/FORS2. similar to 92 objects (88%) have secure redshifts, ranging from 0 to 1.16 with a median value of z sub(med) = 0.587. Considerable care is taken in estimating the extinction properties of individual galaxy, which can seriously affect diagnostic diagrams and estimates of star formation rates (SFRs) and of metal abundances. Two independent estimates of the extinction have been made, e.g. Balmer line ratio and energy balance between infrared (IR) and H beta luminosities. For most of the sources, we find a good agreement between the two extinction coefficients (within plus or minus 0.64 rms in A sub(v), the extinction in V band), with median values of A sub(v)(IR) = 2.36 and A sub(v)(Balmer) = 1.82 for z > 0.4 luminous IR galaxies (LIRGs). At z > 0.4, our sample show many properties (IR luminosity, continuum color, ionization and extinction) strikingly in common with those of local (IRAS) LIRGs studied by Veilleux et al. (1995). Thus, our sample can provide a good representation of LIRGs in the distant Universe. We confirm that most (>77%) ISO 15 mu m-selected galaxies are dominated by star formation. Oxygen abundances in interstellar medium in the galaxies are estimated from the extinction-corrected "strong" emission line ratios (e.g. O II/H beta , O III/H beta and O III/O II). The derived 12+log(O/H) values range from 8.36 to 8.93 for the z > 0.4 galaxies with a median value of 8.67. Distant LIRGs present a metal content less than half of that of the local bright disks (i.e. L*). Their properties can be reproduced with infall models although one has to limit the infall time to avoid overproduction of metals at late times. The models predict that total masses (gas + stars) of the distant LIRGs are from 10 super(11) M to less than or equal to 10 super(12) M . A significant fraction of distant large disks are indeed LIRGs. Such massive disks could have formed similar to 50% of their metals and stellar masses since z similar to 1.
Aims. The total infrared (TIR: 8-1000 \mum) and far-ultraviolet (FUV: similar to 1500 Aa) luminosity functions of galaxies and the related luminosity densities \rho_{\rm TIR} and \rho_{\rm FUV} are ...known to evolve at differemt rates from z = 0 to z similar to 1: the galaxy populations appear to be brighter in the past at both wavelengths, but the evolution in the TIR is larger than in the FUV. This leads to an increase of the ratio of TIR to FUV luminosity densities \rho_{\rm TIR}/\rho_{\rm FUV} which can be interpreted as a global increase of the dust attenuation from z = 0 to z similar to 1. Our aim is to understand the origin of this increase: is it entirely due to a variation of the dust attenuation with the luminosity of the galaxies as seen as z = 0 or are properties of galaxies evolving with the redshift? Methods. We focus on infrared galaxies more luminous than L_{\rm TIR} = 10 super(11) L_{\odot} at z similar to 0.7 observed by SPITZER/MIPS and we measure their ultraviolet emission at 2310 Aa from GALEX images. These Luminous InfraRed Galaxies (LIRGs) represent the bulk of the TIR luminosity density at intermediate redshift. The analysis of the ratio of TIR to FUV (rest-frame) luminosity (L_{\rm TIR}/L_{\rm FUV}) enables us to discuss and compare their dust attenuation to that of galaxies of similar infrared luminosity selected in the same way in the nearby universe Results. Some evolution of L_{\rm TIR}/L_{\rm FUV} and therefore of dust attenuation is found: LIRGs at z = 0.7 span a larger range of L_{\rm TIR}/L_{\rm FUV} ratios than at z = 0 and their mean dust attenuation at FUV wavelengths is found to be similar to 0.5 mag lower than for their local counterparts. The decrease of dust attenuation is found to be less than that reported in other studies for bright galaxies selected in UV rest-frame at z = 1 and 2. A semi-quantitative analysis accounts for the general increase of dust attenuation with the bolometric luminosity of galaxies: it is found that the slight decrease of dust attenuation for LIRGs at z = 0.7 remains consistent with the increase of \rho_{\rm TIR}/\rho_{\rm FUV} with redshift.
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