[C<scp>ii</scp>] 158 Micron Observations of IC 10: Evidence for Hidden Molecular Hydrogen in Irregular Galaxies

Madden, S. C.; Poglitsch, A.; Geis, N.; Stacey, G. J.; Townes, C. H.

doi:10.1086/304247

Cited by 242 publications

(313 citation statements)

References 54 publications

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“…Since H 2 may exist in the C ϩ zones because of self-shielding, the ratio X of H 2 mass to CO Jϭ1 -0 luminosity may be significantly higher in the Magellanic Clouds than in the Galaxy (Israel, 1997). Madden et al (1997) arrive at a similar conclusion from [CII] observations of IC10, an irregular galaxy with low metallicity.…”

Section: ϩ Halos Around Molecular Cores In the Magellanic Clouds Ansupporting

confidence: 85%

Photodissociation regions in the interstellar medium of galaxies

Hollenbach

Tielens²

1999

Rev. Mod. Phys.

728

712

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The interstellar medium of galaxies is the reservoir out of which stars are born and into which stars inject newly created elements as they age. The physical properties of the interstellar medium are governed in part by the radiation emitted by these stars. Far-ultraviolet (6 eVϽh Ͻ13.6 eV) photons from massive stars dominate the heating and influence the chemistry of the neutral atomic gas and much of the molecular gas in galaxies. Predominantly neutral regions of the interstellar medium in which the heating and chemistry are regulated by far ultraviolet photons are termed PhotoDissociation Regions (PDRs). These regions are the origin of most of the non-stellar infrared (IR) and the millimeter and submillimeter CO emission from galaxies. The importance of PDRs has become increasingly apparent with advances in IR and submillimeter astronomy. The IR emission from PDRs includes fine structure lines of C, C ϩ , and O; rovibrational lines of H 2 ; rotational lines of CO; broad mid-IR features of polycyclic aromatic hydrocarbons; and a luminous underlying IR continuum from interstellar dust. The transition of H to H 2 and C ϩ to CO occurs within PDRs. Comparison of observations with theoretical models of PDRs enables one to determine the density and temperature structure, the elemental abundances, the level of ionization, and the radiation field. PDR models have been applied to interstellar clouds near massive stars, planetary nebulae, red giant outflows, photoevaporating planetary disks around newly formed stars, diffuse clouds, the neutral intercloud medium, and molecular clouds in the interstellar radiation field-in summary, much of the interstellar medium in galaxies. Theoretical PDR models explain the observed correlations of the [CII] 158 m with the CO Jϭ1 -0 emission, the CO Jϭ1 -0 luminosity with the interstellar molecular mass, and the [CII] 158 m plus [OI] 63 m luminosity with the IR continuum luminosity. On a more global scale, PDR models predict the existence of two stable neutral phases of the interstellar medium, elucidate the formation and destruction of star-forming molecular clouds, and suggest radiation-induced feedback mechanisms that may regulate star formation rates and the column density of gas through giant molecular clouds. [S0034-6861(99)01001-6] CONTENTS

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Section: ϩ Halos Around Molecular Cores In the Magellanic Clouds Ansupporting

confidence: 85%

Photodissociation regions in the interstellar medium of galaxies

Hollenbach

Tielens²

1999

Rev. Mod. Phys.

728

712

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“…Thus, there could be a non negligeable amount of molecular gas not traced by CO (e.g. Poglitsch et al 1995;Madden et al 1997). In order to reach the D/G value expected by chemical models, a large molecular gas mass on the order of 10 10 M would be required to account for the "missing" gas mass, that is to say an order of magnitude more molecular gas than that deduced from current CO upper limits.…”

Section: Dust-to-gas Mass Ratiosmentioning

confidence: 98%

“…In order to reach the D/G value expected by chemical models, a large molecular gas mass on the order of 10 10 M would be required to account for the "missing" gas mass, that is to say an order of magnitude more molecular gas than that deduced from current CO upper limits. Molecular hydrogen could be embedded in [CII] emiting envelopes as described in Madden et al (1997) for the low-metallicity galaxy IC 10. The high L CII /L CO value ( 4 × 10 5 ) deduced by Bergvall et al (2000) and also seen in other low metallicity galaxies (Madden 2000) is coherent with this theory.…”

Section: Dust-to-gas Mass Ratiosmentioning

confidence: 99%

Probing the dust properties of galaxies up to submillimetre wavelengths

Galametz¹,

Madden²,

Galliano³

et al. 2009

A&A

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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“…The emission is strongly correlated with H 2 [17] and can be used to estimate the H 2 mass. As an example we can have a look at IC 10 where Madden et al [99] speculate that, as a consequence of the strong UV field and low metallicity, small CO cores are formed, surrounded by extensive [C II] emitting regions containing H 2 . H 2 masses based on the CO flux would therefore be severely underestimated.…”

Section: Gas Contentmentioning

confidence: 99%

Star Forming Dwarf Galaxies

Bergvall¹

2011

Astrophysics and Space Science Proceedings

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Star forming dwarf galaxies (SFDGs) have a high gas content and low metallicities, reminiscent of the basic entities in hierarchical galaxy formation scenarios. In the young universe they probably also played a major role in the cosmic reionization. Their abundant presence in the local volume and their youthful character make them ideal objects for detailed studies of the initial stellar mass function (IMF), fundamental star formation processes and its feedback to the interstellar medium. Occasionally we witness SFDGs involved in extreme starbursts, giving rise to strongly elevated production of super star clusters and global superwinds, mechanisms yet to be explored in more detail. SFDGs is the initial state of all dwarf galaxies and the relation to the environment provides us with a key to how different types of dwarf galaxies are emerging. In this review we will put the emphasis on the exotic starburst phase, as it seems less important for present day galaxy evolution but perhaps fundamental in the initial phase of galaxy formation.

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[Cii] 158 Micron Observations of IC 10: Evidence for Hidden Molecular Hydrogen in Irregular Galaxies

Cited by 242 publications

References 54 publications

Photodissociation regions in the interstellar medium of galaxies

Photodissociation regions in the interstellar medium of galaxies

Probing the dust properties of galaxies up to submillimetre wavelengths

Star Forming Dwarf Galaxies

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