The first detection of Far-Infrared emission associated with an extended HI disk. The case of NGC 891

Popescu, Cristina; Tuffs, R.

doi:10.1051/0004-6361:20031443

Cited by 44 publications

(50 citation statements)

References 32 publications

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“…The extended radial distribution of the dust has been confirmed for our Galaxy using COBE/DIRBE data [10]. Analysis of ISO data for several galaxies [1], [27], [28] as well as SCUBA observations of NGC 891 in 450µm and 850µm [2], also indicate a more extended radial distribution for the dust than for the stars. Another interesting result that came out of their analysis was the dust mass.…”

Section: Band Give a Mean Ratio Of Hsupporting

confidence: 65%

Radiation Transfer Models in Galaxies

Kylafis¹,

Xilouris²

2005

AIP Conference Proceedings

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Abstract. The dust in galaxies makes radiation transport calculations in them absolutely necessary. It is not only common practice in Astrophysics, but also wisdom, to try to make as simple models as possible to simulate physical systems. For spiral galaxies, however, this turned out to be catastrophic. For years, the major question of the opacity of spiral galaxies kept the community divided, because the models were too simple. A spiral galaxy appears, to first order, to have exponential distributions of stars and dust, which cannot be approximated with uniform distributions. We will review the radiative transfer methods used in galaxies and we will comment on their pluses and minuses. We will also present some of the main results of the application of one of the methods to the observations.

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Section: Band Give a Mean Ratio Of Hsupporting

confidence: 65%

Radiation Transfer Models in Galaxies

Kylafis¹,

Xilouris²

2005

AIP Conference Proceedings

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“…This has been found in other galaxies before (e.g., M51; Calzetti et al 2005), but it is interesting to note that the same holds true even for faint dwarfs such as Holmberg I. We note that there is also diffuse dust emission present in our objects (e.g., Holmberg II and IC 2574) that is likely heated by the underlying stellar population or by UV photons that are leaking from the H ii regions (see Cannon et al [2006b] for a detailed discussion on the diffuse dust component in the Local Group galaxy NGC 6822; see also, e.g., Popescu et al [2002], Popescu & Tuffs [2003], and Hinz et al [2006]). …”

Section: Spatial Comparison To Hmentioning

confidence: 66%

Dust and Atomic Gas in Dwarf Irregular Galaxies of the M81 Group: The SINGS and THINGS View

Walter

Cannon

Roussel

et al. 2007

ApJ

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We present observations of the dust and atomic gas phase in seven dwarf irregular galaxies of the M81 group from the Spitzer SINGS and VLA THINGS surveys. The Spitzer observations provide a first glimpse of the nature of the nonatomic ISM in these metal-poor (Z $ 0:1 Z ), quiescent (SFR $ 0:001Y0:1 M yr À1 ) dwarf galaxies. Most detected dust emission is restricted to H i column densities >1 ; 10 21 cm À2 , and almost all regions of high H i column density (>2:5 ; 10 21 cm À2 ) have associated dust emission. Spitzer spectroscopy of two regions in the brightest galaxies (IC 2574 and Holmberg II ) show distinctly different spectral shapes and aromatic features, although the galaxies have comparable gas-phase metallicities. This result emphasizes that the strength of the aromatic features is not a simple linear function of metallicity. We estimate dust masses of $10 4 Y10 6 M for the M81 dwarf galaxies, resulting in an average dust-to-gas ratio (M dust /M H i ) of $3 ; 10 À4 (1:5 ; 10 À3 if only the H i that is associated with dust emission is considered); this is an order of magnitude lower than the typical value derived for the SINGS spirals. The dwarf galaxies are underluminous per unit star formation rate at 70 m as compared to the more massive galaxies in SINGS by a factor of $2. However, the average 70/160 m ratio in the sample dwarf galaxies is higher than what is found in the other galaxies of the SINGS sample. This can be explained by a combination of a lower dust content in conjunction with a higher dust temperature in the dwarfs.

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“…In Papers I and II we verified that the derived geometrical parameters from Xilouris et al correctly predicted the dust emission SEDs of the 5 nearby edge-on galaxies. Observationally it was also confirmed that the dust disk not only has a larger scalelength than the stellar disk Davies et al 1999), but was detected to physically extend well beyond the stellar disk (Popescu & Tuffs 2003; see also Hinz et al 2006, for dwarf galaxies). From resolved studies of galaxies it was also found that there is a large scale distribution of diffuse dust having a face-on opacity that decreases with radius (Boissier et al 2004;Popescu et al 2005;Pérez-González et al 2006;Boissier et al 2007;Muñoz-Mateos et al 2009).…”

Section: The Distribution Of Stars and Dustmentioning

confidence: 72%

Modelling the spectral energy distribution of galaxies

Popescu

Tuffs

Dopita

et al. 2011

A&A

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210

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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The first detection of Far-Infrared emission associated with an extended HI disk. The case of NGC 891

Cited by 44 publications

References 32 publications

Radiation Transfer Models in Galaxies

Radiation Transfer Models in Galaxies

Dust and Atomic Gas in Dwarf Irregular Galaxies of the M81 Group: The SINGS and THINGS View

Modelling the spectral energy distribution of galaxies

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