Elodie Giovannoli - Academia.edu (original) (raw)

Papers by Elodie Giovannoli

Http Www Theses Fr, Nov 9, 2011

Je tiens tout d'abord à remercier ma directrice de thèse, Véronique Buat pour avoir m'avoir fourn... more Je tiens tout d'abord à remercier ma directrice de thèse, Véronique Buat pour avoir m'avoir fourni un encadrement d'une qualité rare durant ces trois dernières années, pour sa disponibilité, ses conseils et pour avoir toujours mis mon travail en valeur. Merci également à toute l'équipe «Physique des Galaxies» pour m'avoir si bien accueillie et particulièrement merci à Denis, Sam, Seb, Alessandro, Michel et Médéric pour votre disponibilité, votre patience, pour les discussions enrichissantes et les dicussions plus légères et pour être des chercheurs aussi «cool». Je remercie les membres de mon jury, Daniel Dale, Jakob Walcher, David Elbaz, Olivier Ilbert et Philippe Amram pour avoir accepté de lire ce manuscrit et pour avoir fait le déplacement le jour de ma soutenance. Je remercie mes parents, Viviane et Simon, mes grands-parents, mon frère, Anthony pour m'avoir toujours encouragé dans mon travail et je remercie surtout mon mari Nicolas pour m'avoir soutenu durant ces trois années, et particulièrement pendant ces derniers mois, et pour accepter de me suivre à l'autre bout du monde. Merci à tout le reste de ma famille, belle-famille, oncles, tantes et cousins pour être présents le jour de ma soutenance. Je remercie Laure, la meilleure «collocataire de bureau» que l'on puisse avoir, pour son soutien en toute circonstance, sa bonne humeur journalière, ses conseils en matière de mode et pour les journées «bonbons». Je remercie Mathilde, Jean-Christophe et Pierre-Yves, pour être des amis aussi drôles que surprenants, pour être toujours là quand il le faut et sans qui le quotidien au LAM n'aurait vraiment pas été le même. Merci pour les nombreux fous-rires. Je remercie Anne-Laure, Yannick (alias Robert, Jordan, Roger...etc), François, Stéphane et Dominique pour leurs divertissantes conversations sur les chars militaires entre autres, à l'heure du déjeuner, et accessoirement pour leur précieuse aide pour tout ce qui touche de près où de loin à l'informatique. Je remercie Christian Surace pour avoir toujours su m'offrir des M&M's quand j'en avais besoin... Merci à Ju, Manu, et Marie pour être toujours prêts à fêter tout et n'importe quoi et pour les nombreuses soirées qui ont ponctué ces trois ans et qui sont des souvenirs dont on pourrait parler pendant des heures. Merci à Christine et Gaby pour avoir autant chouchouté les étudiants du LAM et pour votre gentillesse, votre disponibilité et vos compétences. Enfin je remercie tous mes amis pour tout ce qu'ils m'apportent au quotidien et également pour leur soutien, donc merci Marjorie&Stephan,

Photometric data of galaxies ranging from rest-frame far-UV to far-IR allow to derive galaxy prop... more Photometric data of galaxies ranging from rest-frame far-UV to far-IR allow to derive galaxy properties in a robust way by fitting the attenuated stellar emission and the related dust emission at the same time. For this purpose we have written a code which uses model spectra composed of the Maraston stellar population models, synthetic attenuation functions based on a modified

Monthly Notices of the Royal Astronomical Society, 2015

We investigate the star-formation rate (SFR) and stellar mass, M * relation of a star-forming (SF... more We investigate the star-formation rate (SFR) and stellar mass, M * relation of a star-forming (SF) galaxy sample in the XMM-LSS field to z ∼ 3.0 using the near-infrared data from the VISTA Deep Extragalactic Observations (VIDEO) survey. Combining VIDEO with broadband photometry, we use the SED fitting algorithm CIGALE to derive SFRs and M * and have adapted it to account for the full photometric redshift PDF uncertainty. Applying a SF selection using the D4000 index, we find evidence for strong evolution in the normalisation of the SFR-M * relation out to z ∼ 3 and a roughly constant slope of (SFR ∝ M α *) α = 0.69 ± 0.02 to z ∼ 1.7. We find this increases close to unity toward z ∼ 2.65. Alternatively, if we apply a colour selection, we find a distinct turnover in the SFR-M * relation between 0.7 z 2.0 at the high mass end, and suggest that this is due to an increased contamination from passive galaxies. We find evolution of the specific SFR ∝ (1 + z) 2.60 at log 10 (M * /M) ∼ 10.5, out to z 2.4 with an observed flattening beyond z ∼ 2 with increased stellar mass. Comparing to a range of simulations we find the analytical scaling relation approaches, that invoke an equilibrium model, a good fit to our data, suggesting that a continual smooth accretion regulated by continual outflows may be a key driver in the overall growth of SFGs.

We present CIGALE (Burgarella et al. 2005; Noll et al. 2009), a software developed at the Laborat... more We present CIGALE (Burgarella et al. 2005; Noll et al. 2009), a software developed at the Laboratoire d'Astrophysique de Marseille to fit galaxy spectral energy distributions from the rest-frame far-UV to far-IR wavelength range, and to derive some of their physical parameters. We also give some examples of scientific results obtained with CIGALE.

Proceedings of the International Astronomical Union, 2011

With the goal of constructing Star-Formation Rates (SFR) from AKARI Infrared Camera (IRC) data, w... more With the goal of constructing Star-Formation Rates (SFR) from AKARI Infrared Camera (IRC) data, we analyzed an IR-selected GALEX-SDSS-2MASS-AKARI(IRC & Far-Infrared Surveyor) sample of 153 nearby galaxies. The far-infrared fluxes were obtained from AKARI diffuse maps to correct the underestimation for extended sources raised by PSF photometry. SFRs of these galaxies were derived using the SED fitting program CIGALE. In spite of complicated features contained in these bands, both the S9W and L18W emissions correlate with the SFR of galaxies. The SFR calibrations using S9W and L18W are presented for the first time. These calibrations agree well with previous work based on Spitzer data within the scatter, and should be applicable to dust-rich galaxies.

Proceedings of the International Astronomical Union, 2010

Herschel opens a large field of investigations on the hidden star formation in galaxies. Combinin... more Herschel opens a large field of investigations on the hidden star formation in galaxies. Combining UV and far-IR rest-frame data allows us to measure all the star formation in galaxies and to estimate the net dust attenuation. The analysis can be performed from the local universe using far-IR and GALEX surveys to high z (up to z < 2) by combining deep U data with the Herschel observations of the HerMES project. The calibration of dust attenuation, and then star formation rate, is reinvestigated. We present the results of the first analyses performed with Herschel data obtained in the Lockman and COSMOS fields as part of the HerMES project and discuss the reliability of dust attenuation corrections.

Proceedings of the International Astronomical Union, 2011

The combination of far-IR and UV-optical rest-frame data has proved to be very efficient to extra... more The combination of far-IR and UV-optical rest-frame data has proved to be very efficient to extract physical parameters from the SEDs of galaxies. Using Herschel and ancillary data from the Herschel Reference Survey and GOODS-Herschel Key Projects, we show how dust attenuation properties can be estimated inside local galaxies as well as in the distant Universe.

Proceedings of the International Astronomical Union, 2012

Aims. The main aim of this work is the characterization of physical properties of galaxies detect... more Aims. The main aim of this work is the characterization of physical properties of galaxies detected in the far infrared (FIR) in the AKARI Deep Field-South (ADF-S) survey. Methods. Starting from a catalog of the 1 000 brightest ADF-S sources in the WIDES (90µm) AKARI band, we constructed a subsample of galaxies with spectral coverage from the ultraviolet to the far infrared. We then analyzed the multiwavelength properties of this 90µm selected sample of galaxies. For galaxies without known spectroscopic redshifts we computed photometric redshifts using the codes Photometric Analysis for Redshift Estimate (Le PHARE) and Code Investigating GALaxy Emission (CIGALE), tested these photometric redshifts using spectroscopic redshifts, and compared the performances of both codes. To test the reliability of parameters obtained by fitting spectral energy distributions, a mock cataloge was generated. Results. We built a large multiwavelength catalog of more than 500 ADF-S galaxies. We successfully fitted spectral energy distributions of 186 galaxies with χ 2 min < 4, and analyzed the output parameters of the fits. We conclude that our sample consists mostly of nearby actively star-forming galaxies, and all our galaxies have a relatively high metallicity. We estimated photometric redshifts for 113 galaxies from the whole ADF-S sample. Comparing the performance of Le PHARE and CIGALE, we found that CIGALE gives more reliable redshift estimates for our galaxies, which implies that including the IR photometry allows for substantial improvement of photometric redshift estimation.

The AKARI All-Sky Survey provided the first bright point source catalog detected at 90um. Startin... more The AKARI All-Sky Survey provided the first bright point source catalog detected at 90um. Starting from this catalog, we selected galaxies by matching AKARI sources with those in the IRAS PSCz. Next, we have measured total GALEX FUV and NUV flux densities. Then, we have matched this sample with SDSS and 2MASS galaxies. By this procedure, we obtained the final sample which consists of 607 galaxies. If we sort the sample with respect to 90um, their average SED shows a coherent trend: the more luminous at 90um, the redder the global SED becomes. The M_r--NUV-r color-magnitude relation of our sample does not show bimodality, and the distribution is centered on the green valley between the blue cloud and red sequence seen in optical surveys. We have established formulae to convert FIR luminosity from AKARI bands to the total infrared (IR) luminosity L_TIR. With these formulae, we calculated the star formation directly visible with FUV and hidden by dust. The luminosity related to star formation activity (L_SF) is dominated by L_TIR even if we take into account the far-infrared (FIR) emission from dust heated by old stars. At high star formation rate (SFR) (> 20 Msun yr^-1), the fraction of directly visible SFR, SFR_FUV, decreases. We also estimated the FUV attenuation A_FUV from FUV-to-total IR (TIR) luminosity ratio. We also examined the L_TIR/L_FUV-UV slope (FUV- NUV) relation. The majority of the sample has L_TIR/L_FUV ratios 5 to 10 times lower than expected from the local starburst relation, while some LIRGs and all the ULIRGs of this sample have higher L_TIR/L_FUV ratios. We found that the attenuation indicator L_TIR/L_FUV is correlated to the stellar mass of galaxies, M*, but there is no correlation with specific SFR (SSFR), SFR/M*, and dust attenuation L_TIR/L_FUV. (abridged)

Astronomy & Astrophysics, 2010

Luminous InfraRed Galaxies (LIRGs) are particularly important for studying the build-up of the st... more Luminous InfraRed Galaxies (LIRGs) are particularly important for studying the build-up of the stellar mass from z=1 to z=0. We perform a multiwavelength study of an LIRGs sample in the Extended Chandra Deep Field South at z=0.7, selected at 24 \mu\m by MIPS onboard Spitzer Space Telescope and detected in 17 filters. Data go from the near-ultraviolet to the mid-infrared. This multiwavelengths dataset allows us to place strong constraints on the spectral energy distributions (SEDs) of galaxies, and thus to efficiently derive physical parameters such as the SFR, the total infrared luminosity, attenuation parameters, and star formation history. An important part of this work is elaboration of a mock catalogue that allows us to have a reliability criterion for the derived parameters. We studied LIRGs by means of an SED-fitting code CIGALE. At first, this code creates synthetic spectra from the Maraston stellar population models. The stellar population spectra are attenuated by using a synthetic Calzetti-based attenuation law before adding the dust emission as given by the infrared SED library. The originality of CIGALE is that it allows us to perform consistent fits of the dust-affected ultaviolet-to-infrared wavelength range. This technique appears to be a very powerful tool in the case where we can have access to a dataset that is well-sampled over a wide range of wavelengths. We are able to derive a star formation history and to estimate the fraction of infrared luminosity reprocessed by an active galactic nucleus. We study the dust temperatures of our galaxies detected at 70 \mu\m and find them colder than predicted by models. We also study the relation between the SFR and the stellar mass and do not find a tight correlation between either of them, but instead a flat distribution and a large scatter, which is interpreted in terms of variations in star formation history.

Photometric data of galaxies ranging from rest-frame far-UV to far-IR allow to derive galaxy prop... more Photometric data of galaxies ranging from rest-frame far-UV to far-IR allow to derive galaxy properties in a robust way by fitting the attenuated stellar emission and the related dust emission at the same time. For this purpose we have written a code which uses model spectra composed of the Maraston stellar population models, synthetic attenuation functions based on a modified Calzetti law, spectral line templates, and the Dale & Helou dust emission models. Depending on the input redshifts filter fluxes are computed for the model set and compared to the galaxy photometry by carrying out a Bayesian analysis. The code is tested by analysing a subset of the SINGS sample of nearby galaxies. We illustrate the quality of the results by comparing them to literature data and discuss the importance of IR data for the reliability of the fitting.

Photometric data of galaxies covering the rest-frame wavelength range from far-UV to far-IR make ... more 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. 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 are 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. For up to 17 filters between 0.15 and 160 mum, we find robust results for the mass, star formation rate, effective age of the stellar population at 4000 A, bolometric luminosity, luminosity absorbed by dust, and attenuation in the far-UV. 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 10^11 M_sol towards higher total stellar masses. The dustiest sample galaxies are present in the same mass range. [abridged]

Astronomy & Astrophysics, 2010

Aims. We explore spectral energy distributions (SEDs), star formation, and dust extinction proper... more Aims. We explore spectral energy distributions (SEDs), star formation, and dust extinction properties of galaxies in the Local Universe. Methods. The AKARI All-Sky Survey provided the first bright point source catalog detected at 90 µm. Starting from this catalog, we selected galaxies by matching AKARI sources with those in the IRAS PSCz. Next, we have measured total GALEX FUV and NUV flux densities by a photometry software we have specifically developed for this purpose. Then, we have matched this sample with SDSS and 2MASS galaxies. By this procedure, we obtained the basic sample which consists of 776 galaxies. After removing objects with photometry contaminated by foreground sources (mainly in SDSS), we have defined the "secure sample" which contains 607 galaxies. Using this galaxy sample, we have explored various properties of galaxies related to star formation and dust extinction. Results. The sample galaxies have redshifts < ∼ 0.15, and their 90-µm luminosities range from 10 6 to 10 12 L ⊙ , with a peak at 10 10 L ⊙ . The SEDs display a large variety, especially more than four orders of magnitude at M-FIR , but if we sort the sample with respect to 90 µm, their average SED shows a coherent trend: the more luminous at 90 µm, the redder the global SED becomes. The M r -NUV − r color-magnitude relation of our sample does not show bimodality, and the distribution is centered on the green valley between the blue cloud and red sequence seen in optical surveys. We have established formulae to convert FIR luminosity from AKARI bands to the total infrared (IR) luminosity L TIR . With these formulae, we calculated the star formation directly visible with FUV and hidden by dust. The luminosity related to star formation activity (L SF ) is dominated by L TIR even if we take into account the far-infrared (FIR) emission from dust heated by old stars. At high star formation rate (SFR) (> 20 M ⊙ yr −1 ), the fraction of directly visible SFR, SFR FUV , decreases. We also estimated the FUV attenuation A FUV from FUV-to-total IR (TIR) luminosity ratio. We also examined the L TIR /L FUV -UV slope (FUV − NUV) relation. The majority of the sample has L TIR /L FUV ratios 5 to 10 times lower than expected from the local starburst relation, while some LIRGs and all the ULIRGs of this sample have higher L TIR /L FUV ratios. We found that the attenuation indicator L TIR /L FUV is correlated to the stellar mass of galaxies, M * , but there is no correlation with specific SFR (SSFR), SFR/M * , and dust attenuation L TIR /L FUV . Conclusions. Together, these results show that the AKARI FIS All-Sky Survey gives a representative sample of SF galaxies in the Local Universe. This sample will be a comprehensive standard of various properties of SF galaxies to be compared with, e.g., high-z SF galaxies.

Astronomy & Astrophysics, 2009

We select galaxies in UV rest-frame at z=0, z~0.7 and z~1 together with a sample of LBGs at z~1, ... more We select galaxies in UV rest-frame at z=0, z~0.7 and z~1 together with a sample of LBGs at z~1, the samples are built in order to sample the same range of luminosity at any redshift. The evolution of the IR and UV luminosities with z is analysed for individual galaxies as well as in terms of luminosity functions. The L_IR/L_UV ratio is used to measure dust attenuation. This ratio does not exhibit a strong evolution with z for the bulk of our sample galaxies but some trends are found for galaxies with a strong dust attenuation and for UV luminous sources: galaxies with L_IR/L_UV>10 are more frequent at z>0 than at z=0 and the largest values of L_IR/L_UV are found for UV faint objects; conversely the most luminous galaxies of our samples (L_UV> 2 10^{10} L_sun$), detected at z=1, exhibit a lower dust attenuation than the fainter ones. L_IR/L_UV increases with the K rest-frame luminosity of the galaxies at all the redshifts considered and shows a residual anti-correlation with L_UV. The most massive and UV luminous galaxies exhibit quite large specific star formation rates. LBGs exhibit systematically lower dust attenuation than UV selected galaxies of same luminosity but similar specific star formation rates. The analysis of the UV+IR luminosity functions leads to the conclusion that up to z = 1 most of the star formation activity of UV selected galaxies is emitted in IR. Whereas we are able to retrieve all the star formation from our UV selection at z=0.7, at z = 1 we miss a large fraction of galaxies more luminous than ~ 10^{11} L_sun. The effect is found larger for Lyman Break Galaxies.

Astronomy & Astrophysics, 2011

Dust attenuation curves in external galaxies are useful to study their dust properties as well as... more Dust attenuation curves in external galaxies are useful to study their dust properties as well as to interpret their intrinsic spectral energy distributions. In particular the presence or absence of a UV bump at 2175 A remains an open issue which has consequences on the interpretation of broad band colours of distant galaxies. We study the dust attenuation curve in the UV range at z >1. In particular we search for the presence of a UV bump. We use deep photometric data of the CDFS obtained with intermediate and broad band filters by the MUSYC project to sample the UV rest-frame of galaxies with 1<z <2. Herschel/PACS and Spitzer/MIPS data are used to measure the dust emission. 30 galaxies were selected with high S/N in all bands. Their SEDs from the UV to the far-IR are fitted using the CIGALE code and the characteristics of the dust attenuation curve are obtained. The mean dust attenuation curve we derive exhibits a UV bump at 2175A whose amplitude corresponds to 35 % (76%) that of the MW (LMC2 supershell) extinction curve. An analytical expression of the average attenuation curve is given, it is found slightly steeper than the Calzetti et al. one, although at a 1 sigma level. Our galaxy sample is used to study the derivation of the slopes of the UV continuum from broad band colours, including the GALEX FUV-NUV colour. Systematic errors induced by the presence of the bump are quantified. We compare dust attenuation factors measured with CIGALE to the slope of the UV continuum and find that there is a large scatter around the relation valid for local starbursts (0.7 mag). The uncertainties on the determination of the UV slope lead to an extra systematic error of the order of 0.3 to 0.7 mag on dust attenuation when a filter overlaps the UV bump.

Astrophysical Journal, 2011

We introduce a fast Markov Chain Monte Carlo (MCMC) exploration of the astrophysical parameter sp... more We introduce a fast Markov Chain Monte Carlo (MCMC) exploration of the astrophysical parameter space using a modified version of the publicly available code CIGALE (Code Investigating GALaxy emission). The original CIGALE builds a grid of theoretical Spectral Energy Distribution (SED) models and fits to photometric fluxes from Ultraviolet (UV) to Infrared (IR) to put contraints on parameters related to both formation and evolution of galaxies. Such a grid-based method can lead to a long and challenging parameter extraction since the computation time increases exponentially with the number of parameters considered and results can be dependent on the density of sampling points, which must be chosen in advance for each parameter. Markov Chain Monte Carlo methods, on the other hand, scale approximately linearly with the number of parameters, allowing a faster and more accurate exploration of the parameter space by using a smaller number of efficiently chosen samples. We test our MCMC version of the code CIGALE (called CIGALEMC) with simulated data. After checking the ability of the code to retrieve the input parameters used to build the mock sample, we fit theoretical SEDs to real data from the well known and studied SINGS sample. We discuss constraints on the parameters and show the advantages of our MCMC sampling method in terms of accuracy of the results and optimization of CPU time.

Astronomy & Astrophysics, 2011

The nearby universe remains the best laboratory to understand physical properties of galaxies and... more The nearby universe remains the best laboratory to understand physical properties of galaxies and is a reference for any comparison with high redshift observations. The all sky (or very large) surveys performed from the ultraviolet (UV) to the far-infrared (far-IR) gives us large datasets with a very large wavelength coverage to perform a reference study. We want to investigate dust attenuation characteristics as well as star formation rate (SFR) calibrations on a sample of nearby galaxies observed over 13 bands from 0.15 to 160 microns. A sample of 363 galaxies is built from the AKARI /FIS all sky survey cross-correlated with SDSS and GALEX surveys. Broad band spectral energy distributions are fitted with the CIGALE code optimized to analyze variations in dust attenuation curves and SFR measurements and based on an energetic budget between the stellar and dust emission. Our galaxy sample is primarily selected in far-IR and mostly constituted of massive, actively star forming galaxies. There is some evidence for a dust attenuation law slightly steeper than that used for starburst galaxies but we are unable to constrain the presence or not of a bump at 220 nm. We confirm that a time dependent dust attenuation is necessary to perform the best fits. Various calibrations of the dust attenuation in the UV as a function of UV-optical colours are discussed. A calibration of the current star formation rate combining UV and total IR emissions is proposed with an accurate estimation of dust heating by old stars: for the whole sample 17 % of the total dust luminosity is not related to the recent star formation

Astronomy & Astrophysics, 2009

Aims. Photometric data of galaxies covering the rest-frame wavelength range from far-UV to far-IR... more 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.

ABSTRACT We found that the rapid decline of SFR density from z = 1 to z = 0 is accompanied by a r... more ABSTRACT We found that the rapid decline of SFR density from z = 1 to z = 0 is accompanied by a rapid decline of the contribution of infrared (IR) galaxies [1]. Making use of FUV (GALEX) and FIR (IRAS/Spitzer) data, we have established a method to estimate the star-formation luminosity function (LF), that is a LF of galaxy luminosity produced by newly formed stars [1]. In this work, we have calculated the distribution function of SFR of galaxies (SFR function) as a function of redshift at z = 0-1 from UV and FIR selected galaxies in the CDFS. We found that, though the FUV- and FIR-based SFR functions agree until z = 0.7, the FUV-based one becomes significantly lower than FIR based one at z = 1. As for integrated value, this means that the SFR density is at least 40% underestimated, even after adding the contribution from obscured star formation.

Http Www Theses Fr, Nov 9, 2011

Je tiens tout d'abord à remercier ma directrice de thèse, Véronique Buat pour avoir m'avoir fourn... more Je tiens tout d'abord à remercier ma directrice de thèse, Véronique Buat pour avoir m'avoir fourni un encadrement d'une qualité rare durant ces trois dernières années, pour sa disponibilité, ses conseils et pour avoir toujours mis mon travail en valeur. Merci également à toute l'équipe «Physique des Galaxies» pour m'avoir si bien accueillie et particulièrement merci à Denis, Sam, Seb, Alessandro, Michel et Médéric pour votre disponibilité, votre patience, pour les discussions enrichissantes et les dicussions plus légères et pour être des chercheurs aussi «cool». Je remercie les membres de mon jury, Daniel Dale, Jakob Walcher, David Elbaz, Olivier Ilbert et Philippe Amram pour avoir accepté de lire ce manuscrit et pour avoir fait le déplacement le jour de ma soutenance. Je remercie mes parents, Viviane et Simon, mes grands-parents, mon frère, Anthony pour m'avoir toujours encouragé dans mon travail et je remercie surtout mon mari Nicolas pour m'avoir soutenu durant ces trois années, et particulièrement pendant ces derniers mois, et pour accepter de me suivre à l'autre bout du monde. Merci à tout le reste de ma famille, belle-famille, oncles, tantes et cousins pour être présents le jour de ma soutenance. Je remercie Laure, la meilleure «collocataire de bureau» que l'on puisse avoir, pour son soutien en toute circonstance, sa bonne humeur journalière, ses conseils en matière de mode et pour les journées «bonbons». Je remercie Mathilde, Jean-Christophe et Pierre-Yves, pour être des amis aussi drôles que surprenants, pour être toujours là quand il le faut et sans qui le quotidien au LAM n'aurait vraiment pas été le même. Merci pour les nombreux fous-rires. Je remercie Anne-Laure, Yannick (alias Robert, Jordan, Roger...etc), François, Stéphane et Dominique pour leurs divertissantes conversations sur les chars militaires entre autres, à l'heure du déjeuner, et accessoirement pour leur précieuse aide pour tout ce qui touche de près où de loin à l'informatique. Je remercie Christian Surace pour avoir toujours su m'offrir des M&M's quand j'en avais besoin... Merci à Ju, Manu, et Marie pour être toujours prêts à fêter tout et n'importe quoi et pour les nombreuses soirées qui ont ponctué ces trois ans et qui sont des souvenirs dont on pourrait parler pendant des heures. Merci à Christine et Gaby pour avoir autant chouchouté les étudiants du LAM et pour votre gentillesse, votre disponibilité et vos compétences. Enfin je remercie tous mes amis pour tout ce qu'ils m'apportent au quotidien et également pour leur soutien, donc merci Marjorie&Stephan,

Photometric data of galaxies ranging from rest-frame far-UV to far-IR allow to derive galaxy prop... more Photometric data of galaxies ranging from rest-frame far-UV to far-IR allow to derive galaxy properties in a robust way by fitting the attenuated stellar emission and the related dust emission at the same time. For this purpose we have written a code which uses model spectra composed of the Maraston stellar population models, synthetic attenuation functions based on a modified

Monthly Notices of the Royal Astronomical Society, 2015

We investigate the star-formation rate (SFR) and stellar mass, M * relation of a star-forming (SF... more We investigate the star-formation rate (SFR) and stellar mass, M * relation of a star-forming (SF) galaxy sample in the XMM-LSS field to z ∼ 3.0 using the near-infrared data from the VISTA Deep Extragalactic Observations (VIDEO) survey. Combining VIDEO with broadband photometry, we use the SED fitting algorithm CIGALE to derive SFRs and M * and have adapted it to account for the full photometric redshift PDF uncertainty. Applying a SF selection using the D4000 index, we find evidence for strong evolution in the normalisation of the SFR-M * relation out to z ∼ 3 and a roughly constant slope of (SFR ∝ M α *) α = 0.69 ± 0.02 to z ∼ 1.7. We find this increases close to unity toward z ∼ 2.65. Alternatively, if we apply a colour selection, we find a distinct turnover in the SFR-M * relation between 0.7 z 2.0 at the high mass end, and suggest that this is due to an increased contamination from passive galaxies. We find evolution of the specific SFR ∝ (1 + z) 2.60 at log 10 (M * /M) ∼ 10.5, out to z 2.4 with an observed flattening beyond z ∼ 2 with increased stellar mass. Comparing to a range of simulations we find the analytical scaling relation approaches, that invoke an equilibrium model, a good fit to our data, suggesting that a continual smooth accretion regulated by continual outflows may be a key driver in the overall growth of SFGs.

We present CIGALE (Burgarella et al. 2005; Noll et al. 2009), a software developed at the Laborat... more We present CIGALE (Burgarella et al. 2005; Noll et al. 2009), a software developed at the Laboratoire d'Astrophysique de Marseille to fit galaxy spectral energy distributions from the rest-frame far-UV to far-IR wavelength range, and to derive some of their physical parameters. We also give some examples of scientific results obtained with CIGALE.

Proceedings of the International Astronomical Union, 2011

With the goal of constructing Star-Formation Rates (SFR) from AKARI Infrared Camera (IRC) data, w... more With the goal of constructing Star-Formation Rates (SFR) from AKARI Infrared Camera (IRC) data, we analyzed an IR-selected GALEX-SDSS-2MASS-AKARI(IRC & Far-Infrared Surveyor) sample of 153 nearby galaxies. The far-infrared fluxes were obtained from AKARI diffuse maps to correct the underestimation for extended sources raised by PSF photometry. SFRs of these galaxies were derived using the SED fitting program CIGALE. In spite of complicated features contained in these bands, both the S9W and L18W emissions correlate with the SFR of galaxies. The SFR calibrations using S9W and L18W are presented for the first time. These calibrations agree well with previous work based on Spitzer data within the scatter, and should be applicable to dust-rich galaxies.

Proceedings of the International Astronomical Union, 2010

Herschel opens a large field of investigations on the hidden star formation in galaxies. Combinin... more Herschel opens a large field of investigations on the hidden star formation in galaxies. Combining UV and far-IR rest-frame data allows us to measure all the star formation in galaxies and to estimate the net dust attenuation. The analysis can be performed from the local universe using far-IR and GALEX surveys to high z (up to z < 2) by combining deep U data with the Herschel observations of the HerMES project. The calibration of dust attenuation, and then star formation rate, is reinvestigated. We present the results of the first analyses performed with Herschel data obtained in the Lockman and COSMOS fields as part of the HerMES project and discuss the reliability of dust attenuation corrections.

Proceedings of the International Astronomical Union, 2011

The combination of far-IR and UV-optical rest-frame data has proved to be very efficient to extra... more The combination of far-IR and UV-optical rest-frame data has proved to be very efficient to extract physical parameters from the SEDs of galaxies. Using Herschel and ancillary data from the Herschel Reference Survey and GOODS-Herschel Key Projects, we show how dust attenuation properties can be estimated inside local galaxies as well as in the distant Universe.

Proceedings of the International Astronomical Union, 2012

Aims. The main aim of this work is the characterization of physical properties of galaxies detect... more Aims. The main aim of this work is the characterization of physical properties of galaxies detected in the far infrared (FIR) in the AKARI Deep Field-South (ADF-S) survey. Methods. Starting from a catalog of the 1 000 brightest ADF-S sources in the WIDES (90µm) AKARI band, we constructed a subsample of galaxies with spectral coverage from the ultraviolet to the far infrared. We then analyzed the multiwavelength properties of this 90µm selected sample of galaxies. For galaxies without known spectroscopic redshifts we computed photometric redshifts using the codes Photometric Analysis for Redshift Estimate (Le PHARE) and Code Investigating GALaxy Emission (CIGALE), tested these photometric redshifts using spectroscopic redshifts, and compared the performances of both codes. To test the reliability of parameters obtained by fitting spectral energy distributions, a mock cataloge was generated. Results. We built a large multiwavelength catalog of more than 500 ADF-S galaxies. We successfully fitted spectral energy distributions of 186 galaxies with χ 2 min < 4, and analyzed the output parameters of the fits. We conclude that our sample consists mostly of nearby actively star-forming galaxies, and all our galaxies have a relatively high metallicity. We estimated photometric redshifts for 113 galaxies from the whole ADF-S sample. Comparing the performance of Le PHARE and CIGALE, we found that CIGALE gives more reliable redshift estimates for our galaxies, which implies that including the IR photometry allows for substantial improvement of photometric redshift estimation.

The AKARI All-Sky Survey provided the first bright point source catalog detected at 90um. Startin... more The AKARI All-Sky Survey provided the first bright point source catalog detected at 90um. Starting from this catalog, we selected galaxies by matching AKARI sources with those in the IRAS PSCz. Next, we have measured total GALEX FUV and NUV flux densities. Then, we have matched this sample with SDSS and 2MASS galaxies. By this procedure, we obtained the final sample which consists of 607 galaxies. If we sort the sample with respect to 90um, their average SED shows a coherent trend: the more luminous at 90um, the redder the global SED becomes. The M_r--NUV-r color-magnitude relation of our sample does not show bimodality, and the distribution is centered on the green valley between the blue cloud and red sequence seen in optical surveys. We have established formulae to convert FIR luminosity from AKARI bands to the total infrared (IR) luminosity L_TIR. With these formulae, we calculated the star formation directly visible with FUV and hidden by dust. The luminosity related to star formation activity (L_SF) is dominated by L_TIR even if we take into account the far-infrared (FIR) emission from dust heated by old stars. At high star formation rate (SFR) (> 20 Msun yr^-1), the fraction of directly visible SFR, SFR_FUV, decreases. We also estimated the FUV attenuation A_FUV from FUV-to-total IR (TIR) luminosity ratio. We also examined the L_TIR/L_FUV-UV slope (FUV- NUV) relation. The majority of the sample has L_TIR/L_FUV ratios 5 to 10 times lower than expected from the local starburst relation, while some LIRGs and all the ULIRGs of this sample have higher L_TIR/L_FUV ratios. We found that the attenuation indicator L_TIR/L_FUV is correlated to the stellar mass of galaxies, M*, but there is no correlation with specific SFR (SSFR), SFR/M*, and dust attenuation L_TIR/L_FUV. (abridged)

Astronomy & Astrophysics, 2010

Luminous InfraRed Galaxies (LIRGs) are particularly important for studying the build-up of the st... more Luminous InfraRed Galaxies (LIRGs) are particularly important for studying the build-up of the stellar mass from z=1 to z=0. We perform a multiwavelength study of an LIRGs sample in the Extended Chandra Deep Field South at z=0.7, selected at 24 \mu\m by MIPS onboard Spitzer Space Telescope and detected in 17 filters. Data go from the near-ultraviolet to the mid-infrared. This multiwavelengths dataset allows us to place strong constraints on the spectral energy distributions (SEDs) of galaxies, and thus to efficiently derive physical parameters such as the SFR, the total infrared luminosity, attenuation parameters, and star formation history. An important part of this work is elaboration of a mock catalogue that allows us to have a reliability criterion for the derived parameters. We studied LIRGs by means of an SED-fitting code CIGALE. At first, this code creates synthetic spectra from the Maraston stellar population models. The stellar population spectra are attenuated by using a synthetic Calzetti-based attenuation law before adding the dust emission as given by the infrared SED library. The originality of CIGALE is that it allows us to perform consistent fits of the dust-affected ultaviolet-to-infrared wavelength range. This technique appears to be a very powerful tool in the case where we can have access to a dataset that is well-sampled over a wide range of wavelengths. We are able to derive a star formation history and to estimate the fraction of infrared luminosity reprocessed by an active galactic nucleus. We study the dust temperatures of our galaxies detected at 70 \mu\m and find them colder than predicted by models. We also study the relation between the SFR and the stellar mass and do not find a tight correlation between either of them, but instead a flat distribution and a large scatter, which is interpreted in terms of variations in star formation history.

Photometric data of galaxies ranging from rest-frame far-UV to far-IR allow to derive galaxy prop... more Photometric data of galaxies ranging from rest-frame far-UV to far-IR allow to derive galaxy properties in a robust way by fitting the attenuated stellar emission and the related dust emission at the same time. For this purpose we have written a code which uses model spectra composed of the Maraston stellar population models, synthetic attenuation functions based on a modified Calzetti law, spectral line templates, and the Dale & Helou dust emission models. Depending on the input redshifts filter fluxes are computed for the model set and compared to the galaxy photometry by carrying out a Bayesian analysis. The code is tested by analysing a subset of the SINGS sample of nearby galaxies. We illustrate the quality of the results by comparing them to literature data and discuss the importance of IR data for the reliability of the fitting.

Photometric data of galaxies covering the rest-frame wavelength range from far-UV to far-IR make ... more 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. 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 are 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. For up to 17 filters between 0.15 and 160 mum, we find robust results for the mass, star formation rate, effective age of the stellar population at 4000 A, bolometric luminosity, luminosity absorbed by dust, and attenuation in the far-UV. 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 10^11 M_sol towards higher total stellar masses. The dustiest sample galaxies are present in the same mass range. [abridged]

Astronomy & Astrophysics, 2010

Aims. We explore spectral energy distributions (SEDs), star formation, and dust extinction proper... more Aims. We explore spectral energy distributions (SEDs), star formation, and dust extinction properties of galaxies in the Local Universe. Methods. The AKARI All-Sky Survey provided the first bright point source catalog detected at 90 µm. Starting from this catalog, we selected galaxies by matching AKARI sources with those in the IRAS PSCz. Next, we have measured total GALEX FUV and NUV flux densities by a photometry software we have specifically developed for this purpose. Then, we have matched this sample with SDSS and 2MASS galaxies. By this procedure, we obtained the basic sample which consists of 776 galaxies. After removing objects with photometry contaminated by foreground sources (mainly in SDSS), we have defined the "secure sample" which contains 607 galaxies. Using this galaxy sample, we have explored various properties of galaxies related to star formation and dust extinction. Results. The sample galaxies have redshifts < ∼ 0.15, and their 90-µm luminosities range from 10 6 to 10 12 L ⊙ , with a peak at 10 10 L ⊙ . The SEDs display a large variety, especially more than four orders of magnitude at M-FIR , but if we sort the sample with respect to 90 µm, their average SED shows a coherent trend: the more luminous at 90 µm, the redder the global SED becomes. The M r -NUV − r color-magnitude relation of our sample does not show bimodality, and the distribution is centered on the green valley between the blue cloud and red sequence seen in optical surveys. We have established formulae to convert FIR luminosity from AKARI bands to the total infrared (IR) luminosity L TIR . With these formulae, we calculated the star formation directly visible with FUV and hidden by dust. The luminosity related to star formation activity (L SF ) is dominated by L TIR even if we take into account the far-infrared (FIR) emission from dust heated by old stars. At high star formation rate (SFR) (> 20 M ⊙ yr −1 ), the fraction of directly visible SFR, SFR FUV , decreases. We also estimated the FUV attenuation A FUV from FUV-to-total IR (TIR) luminosity ratio. We also examined the L TIR /L FUV -UV slope (FUV − NUV) relation. The majority of the sample has L TIR /L FUV ratios 5 to 10 times lower than expected from the local starburst relation, while some LIRGs and all the ULIRGs of this sample have higher L TIR /L FUV ratios. We found that the attenuation indicator L TIR /L FUV is correlated to the stellar mass of galaxies, M * , but there is no correlation with specific SFR (SSFR), SFR/M * , and dust attenuation L TIR /L FUV . Conclusions. Together, these results show that the AKARI FIS All-Sky Survey gives a representative sample of SF galaxies in the Local Universe. This sample will be a comprehensive standard of various properties of SF galaxies to be compared with, e.g., high-z SF galaxies.

Astronomy & Astrophysics, 2009

We select galaxies in UV rest-frame at z=0, z~0.7 and z~1 together with a sample of LBGs at z~1, ... more We select galaxies in UV rest-frame at z=0, z~0.7 and z~1 together with a sample of LBGs at z~1, the samples are built in order to sample the same range of luminosity at any redshift. The evolution of the IR and UV luminosities with z is analysed for individual galaxies as well as in terms of luminosity functions. The L_IR/L_UV ratio is used to measure dust attenuation. This ratio does not exhibit a strong evolution with z for the bulk of our sample galaxies but some trends are found for galaxies with a strong dust attenuation and for UV luminous sources: galaxies with L_IR/L_UV>10 are more frequent at z>0 than at z=0 and the largest values of L_IR/L_UV are found for UV faint objects; conversely the most luminous galaxies of our samples (L_UV> 2 10^{10} L_sun$), detected at z=1, exhibit a lower dust attenuation than the fainter ones. L_IR/L_UV increases with the K rest-frame luminosity of the galaxies at all the redshifts considered and shows a residual anti-correlation with L_UV. The most massive and UV luminous galaxies exhibit quite large specific star formation rates. LBGs exhibit systematically lower dust attenuation than UV selected galaxies of same luminosity but similar specific star formation rates. The analysis of the UV+IR luminosity functions leads to the conclusion that up to z = 1 most of the star formation activity of UV selected galaxies is emitted in IR. Whereas we are able to retrieve all the star formation from our UV selection at z=0.7, at z = 1 we miss a large fraction of galaxies more luminous than ~ 10^{11} L_sun. The effect is found larger for Lyman Break Galaxies.

Astronomy & Astrophysics, 2011

Dust attenuation curves in external galaxies are useful to study their dust properties as well as... more Dust attenuation curves in external galaxies are useful to study their dust properties as well as to interpret their intrinsic spectral energy distributions. In particular the presence or absence of a UV bump at 2175 A remains an open issue which has consequences on the interpretation of broad band colours of distant galaxies. We study the dust attenuation curve in the UV range at z >1. In particular we search for the presence of a UV bump. We use deep photometric data of the CDFS obtained with intermediate and broad band filters by the MUSYC project to sample the UV rest-frame of galaxies with 1<z <2. Herschel/PACS and Spitzer/MIPS data are used to measure the dust emission. 30 galaxies were selected with high S/N in all bands. Their SEDs from the UV to the far-IR are fitted using the CIGALE code and the characteristics of the dust attenuation curve are obtained. The mean dust attenuation curve we derive exhibits a UV bump at 2175A whose amplitude corresponds to 35 % (76%) that of the MW (LMC2 supershell) extinction curve. An analytical expression of the average attenuation curve is given, it is found slightly steeper than the Calzetti et al. one, although at a 1 sigma level. Our galaxy sample is used to study the derivation of the slopes of the UV continuum from broad band colours, including the GALEX FUV-NUV colour. Systematic errors induced by the presence of the bump are quantified. We compare dust attenuation factors measured with CIGALE to the slope of the UV continuum and find that there is a large scatter around the relation valid for local starbursts (0.7 mag). The uncertainties on the determination of the UV slope lead to an extra systematic error of the order of 0.3 to 0.7 mag on dust attenuation when a filter overlaps the UV bump.

Astrophysical Journal, 2011

We introduce a fast Markov Chain Monte Carlo (MCMC) exploration of the astrophysical parameter sp... more We introduce a fast Markov Chain Monte Carlo (MCMC) exploration of the astrophysical parameter space using a modified version of the publicly available code CIGALE (Code Investigating GALaxy emission). The original CIGALE builds a grid of theoretical Spectral Energy Distribution (SED) models and fits to photometric fluxes from Ultraviolet (UV) to Infrared (IR) to put contraints on parameters related to both formation and evolution of galaxies. Such a grid-based method can lead to a long and challenging parameter extraction since the computation time increases exponentially with the number of parameters considered and results can be dependent on the density of sampling points, which must be chosen in advance for each parameter. Markov Chain Monte Carlo methods, on the other hand, scale approximately linearly with the number of parameters, allowing a faster and more accurate exploration of the parameter space by using a smaller number of efficiently chosen samples. We test our MCMC version of the code CIGALE (called CIGALEMC) with simulated data. After checking the ability of the code to retrieve the input parameters used to build the mock sample, we fit theoretical SEDs to real data from the well known and studied SINGS sample. We discuss constraints on the parameters and show the advantages of our MCMC sampling method in terms of accuracy of the results and optimization of CPU time.

Astronomy & Astrophysics, 2011

The nearby universe remains the best laboratory to understand physical properties of galaxies and... more The nearby universe remains the best laboratory to understand physical properties of galaxies and is a reference for any comparison with high redshift observations. The all sky (or very large) surveys performed from the ultraviolet (UV) to the far-infrared (far-IR) gives us large datasets with a very large wavelength coverage to perform a reference study. We want to investigate dust attenuation characteristics as well as star formation rate (SFR) calibrations on a sample of nearby galaxies observed over 13 bands from 0.15 to 160 microns. A sample of 363 galaxies is built from the AKARI /FIS all sky survey cross-correlated with SDSS and GALEX surveys. Broad band spectral energy distributions are fitted with the CIGALE code optimized to analyze variations in dust attenuation curves and SFR measurements and based on an energetic budget between the stellar and dust emission. Our galaxy sample is primarily selected in far-IR and mostly constituted of massive, actively star forming galaxies. There is some evidence for a dust attenuation law slightly steeper than that used for starburst galaxies but we are unable to constrain the presence or not of a bump at 220 nm. We confirm that a time dependent dust attenuation is necessary to perform the best fits. Various calibrations of the dust attenuation in the UV as a function of UV-optical colours are discussed. A calibration of the current star formation rate combining UV and total IR emissions is proposed with an accurate estimation of dust heating by old stars: for the whole sample 17 % of the total dust luminosity is not related to the recent star formation

Astronomy & Astrophysics, 2009

Aims. Photometric data of galaxies covering the rest-frame wavelength range from far-UV to far-IR... more 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.

ABSTRACT We found that the rapid decline of SFR density from z = 1 to z = 0 is accompanied by a r... more ABSTRACT We found that the rapid decline of SFR density from z = 1 to z = 0 is accompanied by a rapid decline of the contribution of infrared (IR) galaxies [1]. Making use of FUV (GALEX) and FIR (IRAS/Spitzer) data, we have established a method to estimate the star-formation luminosity function (LF), that is a LF of galaxy luminosity produced by newly formed stars [1]. In this work, we have calculated the distribution function of SFR of galaxies (SFR function) as a function of redshift at z = 0-1 from UV and FIR selected galaxies in the CDFS. We found that, though the FUV- and FIR-based SFR functions agree until z = 0.7, the FUV-based one becomes significantly lower than FIR based one at z = 1. As for integrated value, this means that the SFR density is at least 40% underestimated, even after adding the contribution from obscured star formation.