Modelling galaxy spectra in presence of interstellar dust – II. From the ultraviolet to the far-infrared
11 Aug 2006-Monthly Notices of the Royal Astronomical Society (Oxford University Press)-Vol. 370, Iss: 3, pp 1454-1478
TL;DR: In this article, the spectral energy distributions (SEDs) of different morphological types of galaxies are derived by using a simple geometrical model for each type of galaxy, based on a robust model of chemical evolution that assumes a suitable prescription for gas infall, initial mass function, star formation rate and stellar ejecta.
Abstract: In this paper, we present spectrophotometric models for galaxies of different morphological type whose spectral energy distributions (SEDs) take into account the effect of dust in absorbing UV-optical light and re-emitting it in the infrared (IR). The models contain three main components: (i) the diffuse interstellar medium (ISM) composed of gas and dust whose emission and extinction properties have already been studied in detail by Piovan et al. (2006), (ii) the large complexes of molecular clouds (MCs) in which new stars are formed and (iii) the stars of any age and chemical composition. The galaxy models stand on a robust model of chemical evolution that assuming a suitable prescription for gas infall, initial mass function, star formation rate and stellar ejecta provides the total amounts of gas and stars present at any age together with their chemical history. The chemical models are taylored in such a way to match the gross properties of galaxies of different morphological type. In order to describe the interaction between stars and ISM in building up the total SED of a galaxy, one has to know the spatial distribution of gas and stars. This is made adopting a simple geometrical model for each type of galaxy. The total gas and star mass provided by the chemical model are distributed over the whole volume by means of suitable density profiles, one for each component and depending on the galaxy type (spheroidal, disk and disk plus bulge). The galaxy is then split in suitable volume elements to each of which the appropriate amounts of stars, MCs and ISM are assigned. Each elemental volume bin is at the same time source of radiation from the stars inside and absorber and emitter of radiation from and to all other volume bins and the ISM in between. They are the elemental seeds to calculate the total SED. Using the results for the properties of the ISM and the Single Stellar Populations (SSPs) presented by Piovan et al. (2006) we derive the SEDs of galaxies of different morphological type. First the technical details of the method are described and the basic relations driving the interaction between the physical components of the galaxy are presented. Second, the main parameters are examined and their effects on the SED of three prototype galaxies (a disk, an elliptical and a starburster) are highlighted. The final part of the paper is devoted to assess the ability of our galaxy models in reproducing the SEDs of a few real galaxies of the Local Universe.
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TL;DR: In this paper, the effect of bursts and mergers and companion chemical pollution and rejuvenation of the stellar content on the integrated light emitted by galaxies is analyzed using both single stellar populations (SSPs) and simple galaxy models.
Abstract: We investigate the color–magnitude diagram (CMD) of cluster galaxies in the hierarchical Λ-CDM cosmological scenario using both single stellar populations (SSPs) and simple galaxy models. First, we analyze the effect of bursts and mergers and companion chemical pollution and rejuvenation of the stellar content on the integrated light emitted by galaxies. The dispersion of the galaxy magnitudes and colors on the M V − (B − V) plane is mainly due to mixing of ages and metallicities of the stellar populations, with mergers weighting more than bursts of similar mass fractions. The analysis is made using the Monte Carlo technique applied to ideal model galaxies reduced to SSPs with galaxy-size mass to evaluate mass, age, and metallicity of each object. We show that separately determining the contributions by bursts and mergers leads to a better understanding of the observed properties of the CMDs of cluster galaxies. Then we repeat the analysis using suitable chemophotometric models of galaxies whose mass is derived from the cosmological predictions of the galaxy content of typical clusters. Using the halo mass function and the Monte Carlo technique, we derive the formation redshift of each galaxy and its photometric history. These are used to simulate the CMD of the cluster galaxies. The main conclusion is that most massive galaxies have acquired the red color they show today in very early epochs and remained the same ever since. The simulations nicely reproduce the red sequence, green valley, and blue cloud, the three main regions of the CMD in which galaxies crowd.
10 citations
01 Jan 2016
TL;DR: A few naturalists, on the other hand, have believed that species undergo modification, and that the existing forms of life are the descendants by true generation of preexisting forms.
Abstract: Until recently the great majority of naturalists believed that species were immutable productions, and had been separately created. This view has been ably maintained by many authors. Some few naturalists, on the other hand, have believed that species undergo modification, and that the existing forms of life are the descendants by true generation of preexisting forms.
10 citations
TL;DR: In this paper, the stacked spectral energy distribution (SED) of MIPS 24$\mu m$ detected Lyman break galaxies (MIPS-LBGs) is fitted by means of spectro-photometric model GRASIL with an "educated" fitting approach which benefits from results of chemical evolution models.
Abstract: The stacked spectral energy distribution (SED) of Multiband Imaging Photometer for Spitzer (MIPS) 24$\mu m$ detected Lyman break galaxies (MIPS-LBGs) is fitted by means of spectro-photometric model GRASIL with an "educated" fitting approach which benefits from results of chemical evolution models. The star formation rate(SFR)-age-metallicity degeneracies of SED modelling are broken by using SFH and chemical enrichment history suggested by chemical models, which also provide dust mass, dust abundance and chemical elements locked in dust component. We derive the total mass $M_{tot}$, stellar mass $M_{\ast}$, gas mass $M_{g}$, dust mass $M_{d}$, age and SFR of the stacked MIPS-LBG in a self-consistent way. Our estimate of $M_{\ast}= 8\times 10^{10}$ agrees with other works based on UV-optical SED fitting. We suggest that MIPS-LBGs at $z\sim3$ are young (0.3-0.6 Gyr), massive ($M_{tot} \sim 10^{11} M_{\odot}$), dusty ($M_{d} \sim 10^{8} M_{\odot}$), metal rich ($Z \sim Z_{\odot} $) progenitors of elliptical galaxies suffering a strong burst of star formation (SFR $\sim 200 M_{\odot}/yr$). Our estimate of $M_{d}=7 \times 10^{7} M_{\odot}$ of the stacked MIPS-LBG is about a factor of eight lower than the estimated value based on single temperature grey-body fitting, suggesting that self-consistent SED models are needed to estimate dust mass. By comparing with the Milky Way molecular cloud and dust properties, we suggest that denser and dustier environments and flatter dust size distribution are likely in high redshift massive star forming galaxies. These dust properties, as well as the different types of SFHs, can cause different SED shapes between high redshift star-forming ellipticals and local star-burst templates. This discrepancy of SED shapes could in turn explain the non detection at submillimeter wavelengths, of IR luminous ($L_{IR} \succeq 10^{12} L_{\odot} $) MIPS-LBGs.
8 citations
TL;DR: In this paper, the stacked spectral energy distribution (SED) 24 μm Lyman break galaxies (MIPS-LBGs) detected by the Multiband Imaging Photometer for Spitzer (MPS-MIPS) is fitted by means of the spectrophotometric model GRASIL with an "educated" fitting approach which benefits from the results of chemical evolution models.
Abstract: The stacked spectral energy distribution (SED) 24 μm Lyman break galaxies (MIPS-LBGs) detected by the Multiband Imaging Photometer for Spitzer (MIPS) is fitted by means of the spectrophotometric model GRASIL with an "educated" fitting approach which benefits from the results of chemical evolution models. The star formation rate-age-metallicity degeneracies of SED modeling are broken by using star formation history (SFH) and chemical enrichment history suggested by chemical models. The dust mass, dust abundance, and chemical pattern of elements locked in the dust component are also directly provided by chemical models. Using our new "fitting" approach, we derive the total mass M tot, stellar mass M *, gas mass Mg , dust mass Md , age, and star formation rate (SFR) of the stacked MIPS-LBG in a self-consistent way. Our estimate of M * = 8 × 1010 of the stacked MIPS-LBG agrees with other works based on UV-optical SED fitting. We suggest that the MIPS-LBGs at z ~ 3 are young (0.3-0.6 Gyr), massive (M tot ~ 1011 M ☉), dusty (Md ~ 108 M ☉), and metal-rich (Z ~ Z ☉) progenitors of elliptical galaxies undergoing a strong burst of star formation (SFR ~ 200 M ☉ yr–1). Our estimate of Md = 7 × 107 M ☉ of the stacked MIPS-LBG is about a factor of eight lower than the estimated value based on single temperature graybody fitting, suggesting that self-consistent SED models are needed to estimate dust mass. By comparing with Milky Way molecular cloud and dust properties, we suggest that denser and dustier environments and flatter dust size distribution are likely in high-redshift massive star-forming galaxies. These dust properties, as well as the different types of SFHs, can cause different SED shapes between high-redshift star-forming ellipticals and local starburst templates. This discrepancy of SED shapes could in turn explain the non-detection at submillimeter wavelengths of IR luminous (L IR⪰1012 L ☉) MIPS-LBGs.
4 citations
TL;DR: In this paper, a semi-empirical model for the infrared emission of dust around star-forming sites in galaxies is presented, which combines a simple model of radiative transfer in dust clouds with a state-of-the-art model of the microscopic optical properties of dust grains pioneered by Draine & Li.
Abstract: We present a semi-empirical model for the infrared emission of dust around star-forming sites in galaxies. Our approach combines a simple model of radiative transfer in dust clouds with a state-of-the-art model of the microscopic optical pr operties of dust grains pioneered by Draine & Li. In combination with the STARBURST99 stellar spectral synthesis package, this framework is able to produce synthetic spectra for galaxies which extend from the Lyman limit through to the far-infrared. We use it to probe how model galaxy spectra depend upon the physical characteristics of their dust grain populatio ns, and upon the energy sources which heat that dust. We compare the predictions of our model with the 8- and 24-µm luminosities of sources in the Spitzer First Look Survey, and conclude by using the models to analyse the relative merits of various colour diagnostics in distingui shing systems out to a redshift of 2 with ongoing star formation from those with only old stellar populations.
3 citations
References
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TL;DR: In this article, the spectral evolution of stellar populations at ages between 100,000 yr and 20 Gyr at a resolution of 3 A across the whole wavelength range from 3200 to 9500 A for a wide range of metallicities.
Abstract: We present a new model for computing the spectral evolution of stellar populations at ages between 100,000 yr and 20 Gyr at a resolution of 3 A across the whole wavelength range from 3200 to 9500 A for a wide range of metallicities. These predictions are based on a newly available library of observed stellar spectra. We also compute the spectral evolution across a larger wavelength range, from 91 A to 160 micron, at lower resolution. The model incorporates recent progress in stellar evolution theory and an observationally motivated prescription for thermally-pulsing stars on the asymptotic giant branch. The latter is supported by observations of surface brightness fluctuations in nearby stellar populations. We show that this model reproduces well the observed optical and near-infrared colour-magnitude diagrams of Galactic star clusters of various ages and metallicities. Stochastic fluctuations in the numbers of stars in different evolutionary phases can account for the full range of observed integrated colours of star clusters in the Magellanic Clouds. The model reproduces in detail typical galaxy spectra from the Early Data Release (EDR) of the Sloan Digital Sky Survey (SDSS). We exemplify how this type of spectral fit can constrain physical parameters such as the star formation history, metallicity and dust content of galaxies. Our model is the first to enable accurate studies of absorption-line strengths in galaxies containing stars over the full range of ages. Using the highest-quality spectra of the SDSS EDR, we show that this model can reproduce simultaneously the observed strengths of those Lick indices that do not depend strongly on element abundance ratios [abridged].
10,384 citations
TL;DR: The Sloan Digital Sky Survey (SDSS) as mentioned in this paper provides the data to support detailed investigations of the distribution of luminous and non-luminous matter in the Universe: a photometrically and astrometrically calibrated digital imaging survey of pi steradians above about Galactic latitude 30 degrees in five broad optical bands.
Abstract: The Sloan Digital Sky Survey (SDSS) will provide the data to support detailed investigations of the distribution of luminous and non- luminous matter in the Universe: a photometrically and astrometrically calibrated digital imaging survey of pi steradians above about Galactic latitude 30 degrees in five broad optical bands to a depth of g' about 23 magnitudes, and a spectroscopic survey of the approximately one million brightest galaxies and 10^5 brightest quasars found in the photometric object catalog produced by the imaging survey. This paper summarizes the observational parameters and data products of the SDSS, and serves as an introduction to extensive technical on-line documentation.
10,039 citations
Donald G. York1, Jennifer Adelman2, John E. Anderson2, Scott F. Anderson3 +148 more•Institutions (29)
TL;DR: The Sloan Digital Sky Survey (SDSS) as discussed by the authors provides the data to support detailed investigations of the distribution of luminous and non-luminous matter in the universe: a photometrically and astrometrically calibrated digital imaging survey of π sr above about Galactic latitude 30° in five broad optical bands to a depth of g' ~ 23 mag.
Abstract: The Sloan Digital Sky Survey (SDSS) will provide the data to support detailed investigations of the distribution of luminous and nonluminous matter in the universe: a photometrically and astrometrically calibrated digital imaging survey of π sr above about Galactic latitude 30° in five broad optical bands to a depth of g' ~ 23 mag, and a spectroscopic survey of the approximately 106 brightest galaxies and 105 brightest quasars found in the photometric object catalog produced by the imaging survey. This paper summarizes the observational parameters and data products of the SDSS and serves as an introduction to extensive technical on-line documentation.
9,835 citations
TL;DR: Starburst99 as mentioned in this paper is a comprehensive set of model predictions for spectrophotometric and related properties of galaxies with active star formation, which is an improved and extended version of the data set previously published by Leitherer & Heckman.
Abstract: Starburst99 is a comprehensive set of model predictions for spectrophotometric and related properties of galaxies with active star formation. The models are an improved and extended version of the data set previously published by Leitherer & Heckman. We have upgraded our code by implementing the latest set of stellar evolution models of the Geneva group and the model atmosphere grid compiled by Lejeune et al. Several predictions which were not included in the previous publication are shown here for the first time. The models are presented in a homogeneous way for five metallicities between Z = 0.040 and 0.001 and three choices of the initial mass function. The age coverage is 106—109 yr. We also show the spectral energy distributions which are used to compute colors and other quantities. The full data set is available for retrieval at a Web site, which allows users to run specific models with nonstandard parameters as well. We also make the source code available to the community.
4,212 citations
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