ISM properties in low-metallicity environments

Madden, S.; Galliano, F.; Jones, A. P.; Sauvage, M.

doi:10.1051/0004-6361:20053890

Cited by 310 publications

(474 citation statements)

References 86 publications

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“…This is also evidenced by the high global value of the Ne[III]/[NeII] ratio (ratio > 1), already seen in other low metallicity dwarf galaxies (Madden et al 2006), which is normally an indication of the hard interstellar radiation field dominated by a young (<5 Myr) stellar population. The peak of the IR SED compares to that of the 1/40 Z galaxy SBS0335-052 (Houck et al 2004) or IC 10 NW (Parkin et al 2009, in prep.).…”

Section: Results Of the Fiducial Sed Modellingmentioning

confidence: 64%

“…The SED results presented here are obtained using the Galactic shape of the ISRF (Mathis et al 1983), but this may not be accurate in our case for metal-poor galaxies. Modeled ISRFs of dwarf galaxies show that dwarf galaxies can certainly have harder global average ISRFs than that of the Galaxy (Madden et al 2006) -an effect attributed to the lower dust attenuation in the low metallicity ISM and, as a consequence, the larger mean free path length of the ionising photons. As we are modelling galaxies on the global scale here, we test several ISRFs which have been determined for low metallicity galaxies to quantify this dependence.…”

Section: Robustness Of the Results With The Assumed Radiation Fieldmentioning

confidence: 99%

“…The 6.3, 7.6, 8.2 and 11.3 μm PAH features are clearly detected as well as significant emission lines. Note that NeIII/NeII ratio = 3.2 (calculated on the IRS spectrum), which is an indication of the hard radiation field dominated by a young population ≤5 Myr (Madden et al 2006). …”

Section: Irsmentioning

confidence: 92%

“…Madden 2005;Engelbracht et al 2005;Wu et al 2007;Engelbracht et al 2008) compared to metal-rich galaxies, in spite of the role the smallest grains play in the energy balance of galaxies (Rubin et al 2009). Some studies suggest that PAH emission depends on the hardness or strengh of the illuminating radiation field (Madden et al 2006;Engelbracht et al 2008;Gordon et al 2008;Bendo et al 2008). The consequence of lowering the metallicity of a galaxy is the decrease in dust opacity resulting in harder and stronger radiation fields.…”

Section: Introductionmentioning

confidence: 99%

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Probing the dust properties of galaxies up to submillimetre wavelengths

Galametz¹,

Madden²,

Galliano³

et al. 2009

A&A

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200

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Aims. We study the dust properties of four low metallicity galaxies by modelling their spectral energy distributions. This modelling enables us to constrain the dust properties such as the mass, the temperature or the composition to characterise the global ISM properties in dwarf galaxies. Methods. We present 870 μm images of four low metallicity galaxies (NGC 1705, Haro 11, Mrk 1089 and UM 311) observed with the Large APEX BOlometer CAmera (LABOCA) on the Atacama Pathfinder EXperiment (APEX) telescope. We modeled their spectral energy distributions combining the submm observations of LABOCA, 2MASS, IRAS, Spitzer photometric data, and the IRS data for Haro 11. Results. We found that the PAH mass abundance is very low in these galaxies, 5 to 50 times lower than the PAH mass fraction of our Galaxy. We also found that a significant mass of dust is revealed when using submm constraints compared to that measured with only mid-IR to far-IR observations extending only to 160 μm. For NGC 1705 and Haro 11, an excess in submillimeter wavelengths was detected when we used our standard dust SED model. We rerun our SED procedure adding a cold dust component (10 K) to better describe the high 870 μm flux derived from LABOCA observations, which significantly improves the fit. We found that at least 70% of the dust mass of these two galaxies can reside in a cold dust component. We also showed that the subsequent dust-to-gas mass ratios, considering HI and CO observations, can be strikingly high for Haro 11 in comparison with what is usually expected for these low-metallicity environments. Furthermore, we derived the star formation rate of our galaxies and compared them to the Schmidt law. Haro 11 falls anomalously far from the Schmidt relation. These results may suggest that a reservoir of hidden gas could be present in molecular form not traced by the current CO observations. While there can be a significant cold dust mass found in Haro 11, the SED peaks at exceptionally short wavelengths (36 μm), also highlighting the importance of the much warmer dust component heated by the massive star clusters in Haro 11. We also derived the total IR luminosities derived from our models and compared them with relations that derive this luminosity from Spitzer bands. We found that the Draine & Li (2007) formula compares well to our direct IR determinations.

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Section: Results Of the Fiducial Sed Modellingmentioning

confidence: 64%

Section: Robustness Of the Results With The Assumed Radiation Fieldmentioning

confidence: 99%

Section: Irsmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

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Probing the dust properties of galaxies up to submillimetre wavelengths

Galametz¹,

Madden²,

Galliano³

et al. 2009

A&A

Self Cite

200

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show abstract

“…are best match by models with young instantaneous bursts rather than continuous star formation models which systematically over-predict this ratio. ] 122 ratios are higher in the dwarf galaxies than in metal-rich galaxies, which is a clear indication of harder radiation fields (e.g., Madden et al 2006). At low metallicity, the model predictions for those line ratios are higher by a factor of ∼5 than in the high-metallicity grid (for a given set of n H and U) because the radiation field of the starburst is harder.…”

Section: Conditions In the H  Region: High-metallicity Casementioning

confidence: 94%

TheHerschelDwarf Galaxy Survey

Cormier

Madden

Lebouteiller

et al. 2015

A&A

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399

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Context. The far-infrared (FIR) lines are important tracers of the cooling and physical conditions of the interstellar medium (ISM) and are rapidly becoming workhorse diagnostics for galaxies throughout the universe. There are clear indications of a different behavior of these lines at low metallicity that needs to be explored. Aims. Our goal is to explain the main differences and trends observed in the FIR line emission of dwarf galaxies compared to more metal-rich galaxies, and how this translates in ISM properties. ] 57 µm fine-structure cooling lines in a sample of 48 low-metallicity star-forming galaxies of the guaranteed time key program Dwarf Galaxy Survey. We correlate PACS line ratios and line-to-L TIR ratios with L TIR , L TIR /L B , metallicity, and FIR color, and interpret the observed trends in terms of ISM conditions and phase filling factors with Cloudy radiative transfer models. Results. We find that the FIR lines together account for up to 3 percent of L TIR and that star-forming regions dominate the overall emission in dwarf galaxies. Compared to metal-rich galaxies, the ratios of Harboring compact phases of a low filling factor and a large volume filling factor of diffuse gas, the ISM of low-metallicity dwarf galaxies has a more porous structure than that of metal-rich galaxies. Methods

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Spitzer Survey of the Large Magellanic Cloud: Surveying the Agents of a Galaxy’s Evolution (SAGE): Initial Results

Meixner

Indebetouw

Whitney³

et al. 2008

Astrophysics and Space Science Proceedings

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We are performing a uniform and unbiased imaging survey of the Large Magellanic Cloud (LMC, ~7°×7°), using the IRAC (3.6, 4.5, 5.8 and 8 µm) and MIPS (24, 70, and 160 µm) instruments on board the Spitzer Space Telescope (Spitzer) in order to survey the agents of a galaxy's evolution (SAGE), the interstellar medium (ISM) and stars in the LMC. This paper provides an overview of the SAGE legacy project including observing strategy, data processing and initial results. Three key science goals determined the coverage and depth of the survey. The detection of diffuse ISM with column densities >1.2x10 21 H cm -2 permits detailed studies of dust processes in the ISM. SAGE's point source sensitivity enables a complete census of newly formed stars with masses >3 M  that will determine the current star formation rate in the LMC. SAGE's detection of evolved stars with mass loss rates >1x10 -8 M  yr -1 will quantify the rate at which evolved stars inject mass into the ISM of the LMC. The observing strategy includes two epochs in 2005, separated by three months, that both mitigate instrumental artifacts and constrain source variability. The SAGE data are non-proprietary. The data processing includes IRAC and MIPS pipelines and a database for mining the point source catalogs, which will be released to the community in support of Spitzer proposal cycles 4 and 5. We present initial results on the epoch 1 data for a region near N79 and N83. The MIPS 70 and 160 µm images of the diffuse dust emission of the N79/N83 region reveal a similar distribution to the gas emissions, especially the HI 21 cm emission. The measured point source sensitivity for the epoch 1 data is consistent with expectations for the survey. The point source counts are highest for the IRAC 3.6 µm band and decrease dramatically towards longer wavelengths consistent with the fact that stars dominate the point source catalogs and that the dusty objects detected at the longer wavelengths are rare in comparison. The SAGE epoch 1 point source catalog has ~4×10 6 sources and more are anticipated when the epoch 1 and 2 data are combined. Using Milky Way (MW) templates as a guide, we adopt a simplified point source classification to identify three candidate groups, stars without dust, dusty evolved stars and young stellar objects, that offers a starting point for this work. We outline a strategy for identifying foreground MW stars, that may comprise as much as 18% of the source list, and background galaxies , that may comprise ~12% of the source list.

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ISM properties in low-metallicity environments

Cited by 310 publications

References 86 publications

Probing the dust properties of galaxies up to submillimetre wavelengths

Probing the dust properties of galaxies up to submillimetre wavelengths

TheHerschelDwarf Galaxy Survey

Spitzer Survey of the Large Magellanic Cloud: Surveying the Agents of a Galaxy’s Evolution (SAGE): Initial Results

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