Modelling the SEDs of spiral galaxies

Popescu, Cristina; Tuffs, R.

doi:10.1051/eas:0934018

Cited by 3 publications

(3 citation statements)

References 44 publications

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“…Their infrared component, however, considerable overpredicts the 250 µm measurements from BLAST (Marsden et al 2009) and COBE (Fixsen et al 1998). Disentangling the dust extinction from these two different populations, using the realistic Driver et al (2008) (or the Popescu & Tuffs 2009) model would be considerably more complicated. Furthermore, greater dust emission may contradict the luminosity density data at low z (Fig.…”

Section: Comparison With Other Modelsmentioning

confidence: 97%

“…We assume cosmological parameters H 0 = 70 km s −1 Mpc −3 , Ω m = 0.3, and Ω Λ = 0.7. Driver et al (2008) have applied the dust model of Popescu & Tuffs (2009) to a survey of ∼ 10 5 nearby galaxies from the Millennium Galaxy Catalog (Allen et al 2006) to determine the wavelengthdependent escape fraction of photons in the local universe. RDF09 have fit this with a series of power-laws and we use this to compute f esc (ǫ).…”

Section: Direct Starlight Emissionmentioning

confidence: 99%

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Modeling the Extragalactic Background Light From Stars and Dust

Finke

Razzaque

Dermer

2010

ApJ

542

660

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The extragalactic background light (EBL) from the far infrared through the visible and extending into the ultraviolet is thought to be dominated by starlight, either through direct emission or through absorption and reradiation by dust. This is the most important energy range for absorbing γ-rays from distant sources such as blazars and gamma-ray bursts and producing electron-positron pairs. In previous work we presented EBL models in the optical through ultraviolet by consistently taking into account the star formation rate (SFR), initial mass function (IMF) and dust extinction, and treating stars on the main sequence as blackbodies. This technique is extended to include post-main sequence stars and reprocessing of starlight by dust. In our simple model, the total energy absorbed by dust is assumed to be re-emitted as three blackbodies in the infrared, one at 40 K representing warm, large dust grains, one at 70 K representing hot, small dust grains, and one at 450 K representing polycyclic aromatic hydrocarbons. We find our best fit model combining the Hopkins and Beacom SFR using the Cole et al. parameterization with the Baldry and Glazebrook IMF agrees with available luminosity density data at a variety of redshifts. Our resulting EBL energy density is quite close to the lower limits from galaxy counts and in some cases below the lower limits, and agrees fairly well with other recent EBL models shortward of about 5 µm. Deabsorbing TeV γ-ray spectra of various blazars with our EBL model gives results consistent with simple shock acceleration theory. We also find that the universe should be optically thin to γ-rays with energies less than 20 GeV.

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Section: Comparison With Other Modelsmentioning

confidence: 97%

Section: Direct Starlight Emissionmentioning

confidence: 99%

Modeling the Extragalactic Background Light From Stars and Dust

Finke

Razzaque

Dermer

2010

ApJ

542

660

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“…For a history of dust modelling in spiral galaxies see the introduction of either T04 or Pierini et al (2004). A more recent discussion of the T04 model can be found in Popescu & Tuffs (2009).…”

Section: Photometric Models For Dust Attenuation In Spiral Galaxiesmentioning

confidence: 99%

Galaxy Zoo: dust in spiral galaxies★

Masters¹,

Nichol²,

Bamford³

et al. 2010

Monthly Notices of the Royal Astronomical Society

141

168

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We investigate the effect of dust on spiral galaxies by measuring the inclination dependence of optical colours for 24 276 well‐resolved Sloan Digital Sky Survey (SDSS) galaxies visually classified via the Galaxy Zoo project. We find clear trends of reddening with inclination which imply a total extinction from face‐on to edge‐on of 0.7, 0.6, 0.5 and 0.4 mag for the ugri passbands (estimating 0.3 mag of extinction in z band). We split the sample into ‘bulgy’ (early‐type) and ‘discy’ (late‐type) spirals using the SDSS fracdeV (or fDeV) parameter and show that the average face‐on colour of ‘bulgy’ spirals is redder than the average edge‐on colour of ‘discy’ spirals. This shows that the observed optical colour of a spiral galaxy is determined almost equally by the spiral type (via the bulge–disc ratio and stellar populations), and reddening due to dust. We find that both luminosity and spiral type affect the total amount of extinction, with discy spirals at Mr∼−21.5 mag having the most reddening – more than twice as much as both the lowest luminosity and most massive, bulge‐dominated spirals. An increase in dust content is well known for more luminous galaxies, but the decrease of the trend for the most luminous has not been observed before and may be related to their lower levels of recent star formation. We compare our results with the latest dust attenuation models of Tuffs et al. We find that the model reproduces the observed trends reasonably well but overpredicts the amount of u‐band attenuation in edge‐on galaxies. This could be an inadequacy in the Milky Way extinction law (when applied to external galaxies), but more likely indicates the need for a wider range of dust–star geometries. We end by discussing the effects of dust on large galaxy surveys and emphasize that these effects will become important as we push to higher precision measurements of galaxy properties and their clustering.

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Modelling the spectral energy distribution of galaxies

Popescu

Tuffs

Dopita

et al. 2011

A&A

207

454

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We present a self-consistent model of the spectral energy distributions (SEDs) of spiral galaxies from the ultraviolet (UV) to the mid-infrared (MIR)/far-infrared (FIR)/submillimeter (submm) based on a full radiative transfer calculation of the propagation of starlight in galaxy disks. This model predicts not only the total integrated energy absorbed in the UV/optical and re-emitted in the infrared/submm, but also the colours of the dust emission based on an explicit calculation of the strength and colour of the UV/optical radiation fields heating the dust, and incorporating a full calculation of the stochastic heating of small dust grains and PAH molecules. The geometry of the translucent components of the model is empirically constrained using the results from the radiation transfer analysis of Xilouris et al. on spirals in the middle range of the Hubble sequence, while the geometry of the optically thick components is constrained from physical considerations with a posteriori checks of the model predictions with observational data. Following the observational constraints, the model has both a distribution of diffuse dust associated with the old and young disk stellar populations as well as a clumpy component arising from dust in the parent molecular clouds in star forming regions. In accordance with the fragmented nature of dense molecular gas in typical star-forming regions, UV light from massive stars is allowed to either freely stream away into the diffuse medium in some fraction of directions or be geometrically blocked and locally absorbed in clumps. These geometrical constraints enable the dust emission to be predicted in terms of a minimum set of free parameters: the central face-on dust opacity in the B-band τ f B , a clumpiness factor F for the star-forming regions, the star-formation rate SFR, the normalised luminosity of the old stellar population old and the bulge-to-disk ratio B/D. We show that these parameters are almost orthogonal in their predicted effect on the colours of the dust/PAH emission. In most practical applications B/D will actually not be a free parameter but (together with the angular size θ gal and inclination i of the disk) act as a constraint derived from morphological decomposition of higher resolution optical images. This also extends the range of applicability of the model along the Hubble sequence. We further show that the dependence of the dust emission SED on the colour of the stellar photon field depends primarily on the ratio between the luminosities of the young and old stellar populations (as specified by the parameters SFR and old) rather than on the detailed colour of the emissions from either of these populations. The model is thereby independent of a priori assumptions of the detailed mathematical form of the dependence of SFR on time, allowing UV/optical SEDs to be dereddened without recourse to population synthesis models. Utilising these findings, we show how the predictive power of radiative transfer calculations can be combined with measurements of θ ...

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Modelling the SEDs of spiral galaxies

Cited by 3 publications

References 44 publications

Modeling the Extragalactic Background Light From Stars and Dust

Modeling the Extragalactic Background Light From Stars and Dust

Galaxy Zoo: dust in spiral galaxies★

Modelling the spectral energy distribution of galaxies

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