Spitzer survey of the Large Magellanic Cloud, Surveying the Agents of a Galaxy's Evolution (sage). IV. Dust properties in the interstellar medium

被引：141

作者：

Bernard, Jean-Philippe ^{[1
]}

Reach, William T. ^{[2
]}

Paradis, Deborah ^{[1
]}

Meixner, Margaret ^{[3
]}

Paladini, Roberta ^{[2
]}

Kawamura, Akiko ^{[4
]}

Onishi, Toshikazu ^{[4
]}

Vijh, Uma

Gordon, Karl ^{[5
]}

Indebetouw, Remy ^{[6
]}

Hora, Joseph L. ^{[7
]}

Whitney, Barbara ^{[8
]}

Blum, Robert ^{[9
]}

Meade, Marilyn ^{[10
]}

Babler, Brian ^{[10
]}

Churchwell, Ed B. ^{[10
]}

Engelbracht, Charles W. ^{[5
]}

For, Bi-Qing ^{[5
]}

Misselt, Karl ^{[5
]}

Leitherer, Claus ^{[3
]}

Cohen, Martin ^{[11
]}

Boulandger, Francois ^{[12
]}

Frogel, Jay A. ^{[13
]}

Fukui, Yasuo ^{[4
]}

Gallagher, Jay ^{[8
]}

Gorjian, Varoujan ^{[14
]}

Harris, Jason ^{[5
]}

Kelly, Douglas ^{[5
]}

Latter, William B. ^{[2
]}

Madden, Suzanne ^{[15
]}

Markwick-Kemper, Ciska ^{[6
]}

Mizuno, Akira ^{[4
]}

Mizuno, Norikazu ^{[4
]}

Mould, Jeremy ^{[16
]}

Nota, Antonella ^{[3
]}

Oey, M. S. ^{[17
]}

Olsen, Knut ^{[5
]}

Panagia, Nino ^{[3
]}

Perez-Gonzalez, Pablo ^{[5
]}

Shibai, Hiroshi ^{[4
]}

Sato, Shuji ^{[4
]}

Smith, Linda ^{[18
]}

Staveley-Smith, Lister ^{[19
]}

Tielens, A. G. G. M. ^{[20
]}

Ueta, Toshiya ^{[20
]}

Van Dyk, Schuyler ^{[2
]}

Volk, Kevin ^{[21
]}

Werner, Michael ^{[14
]}

Zaritsky, Dennis ^{[5
]}

机构：

[1] CESR, Toulouse, France

[2] CALTECH, Spitzer Sci Ctr, Pasadena, CA 91125 USA

[3] Space Telescope Sci Inst, Baltimore, MD 21218 USA

[4] Nagoya Univ, Dept Astrophys, Chikusa Ku, Nagoya, Aichi 46401, Japan

[5] Univ Arizona, Steward Observ, Tucson, AZ 85721 USA

[6] Univ Virginia, Dept Astron, Charlottesville, VA 22903 USA

[7] Harvard Smithsonian, CfA, Cambridge, MA 02138 USA

[8] Space Sci Inst, Boulder, CO 80301 USA

[9] Cerro Tololo Interamer Observ, La Serena, Chile

[10] Univ Wisconsin, Dept Astron, Madison, WI 53706 USA

[11] Univ Calif Berkeley, Radio Astron Lab, Berkeley, CA 94720 USA

[12] Univ Paris 11, Inst Astrophs Spatiale, Orsay, France

[13] AURA Inc, Washington, DC 20005 USA

[14] CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA

[15] CENS, Serv Astrophys, F-91191 Gif Sur Yvette, France

[16] Natl Opt Astron Observ, Tucson, AZ 85726 USA

[17] Univ Michigan, Dept Astron, Ann Arbor, MI 48109 USA

[18] UCL, Dept Phys & Astron, London WC1E 6BT, England

[19] CSIRO, Head Off, Melbourne, Vic 3001, Australia

[20] NASA, Ames Res Ctr, Moffett Field, CA 94035 USA

[21] No Operat Ctr, Gemini Observ, Hilo, HI 96720 USA

来源：

ASTRONOMICAL JOURNAL | 2008年 / 136卷 / 03期

基金：

英国科学技术设施理事会;

关键词：

galaxies : ISM; infrared : galaxies; infrared : ISM; ISM : abundances; ISM : clouds magellanic clouds;

D O I：

10.1088/0004-6256/136/3/919

中图分类号：

P1 [天文学];

学科分类号：

0704 ;

摘要：

The goal of this paper is to present the results of a preliminary analysis of the extended infrared (IR) emission by dust in the interstellar medium ( ISM) of the Large Magellanic Cloud (LMC). We combine Spitzer Surveying the Agents of Galaxy Evolution ( SAGE) and Infrared Astronomical Satellite ( IRAS) data and correlate the infrared emission with gas tracers of Hi, CO, and H a. We present a global analysis of the infrared emission as well as detailed modeling of the spectral energy distribution ( SED) of a few selected regions. Extended emission by dust associated with the neutral, molecular, and diffuse ionized phases of the ISM is detected at all IR bands from 3.6 mu m to 160 mu m. The relative abundance of the various dust species appears quite similar to that in the Milky Way ( MW) in all the regions we have modeled. We construct maps of the temperature of large dust grains. The temperature map shows variations in the range 12.1-34.7 K, with a systematic gradient from the inner to outer regions, tracing the general distribution of massive stars and individual H II regions as well as showing warmer dust in the stellar bar. This map is used to derive the far-infrared ( FIR) optical depth of large dust grains. We find two main departures in the LMC with respect to expectations based on the MW: ( 1) excess mid-infrared (MIR) emission near 70 mu m, referred to as the 70 mu m excess, and ( 2) departures from linear correlation between the FIR optical depth and the gas column density, which we refer to as FIR excess emission. The 70 mu m excess increases gradually from the MW to the LMC to the Small Magellanic Cloud (SMC), suggesting evolution with decreasing metallicity. The excess is associated with the neutral and diffuse ionized gas, with the strongest excess region located in a loop structure next to 30 Dor. We show that the 70 mu m excess can be explained by a modification of the size distribution of very small grains with respect to that in the MW, and a corresponding mass increase of similar or equal to 13% of the total dust mass in selected regions. The most likely explanation is that the 70 mu m excess is due to the production of large very small grains (VSG) through erosion of larger grains in the diffuse medium. This FIR excess could be due to intrinsic variations of the dust/gas ratio, which would then vary from 4.6 to 2.3 times lower than the MW values across the LMC, but X-CO values derived from the IR emission would then be about three times lower than those derived from the Virial analysis of the CO data. We also investigate the possibility that the FIR excess is associated with an additional gas component undetected in the available gas tracers. Assuming a constant dust abundance in all ISM phases, the additional gas component would have twice the known H I mass. We show that it is plausible that the FIR excess is due to cold atomic gas that is optically thick in the 21 cm line, while the contribution by a pure H-2 phase with no CO emission remains a possible explanation.

引用

页码：919 / 945

页数：27

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