The herschel Virgo cluster survey: IX. Dust-to-gas mass ratio and metallicity gradients in four Virgo spiral galaxies
Por:
Magrini L., Bianchi S., Corbelli E., Cortese L., Hunt L., Smith M., Vlahakis C., Davies J., Bendo G.J., Baes M., Boselli A., Clemens M., Casasola V., De Looze I., Fritz J., Giovanardi C., Grossi M., Hughes T., Madden S., Pappalardo C., Pohlen M., Di Serego Alighieri S., Verstappen J.
Publicada:
1 ene 2011
Resumen:
Context. Using Herschel data from the open time key project the Herschel Virgo Cluster Survey (HeViCS), we investigated the relationship between the metallicity gradients expressed by metal abundances in the gas phase as traced by the chemical composition of HII regions, and in the solid phase, as traced by the dust-to-gas mass ratio. Aims. We derived the radial gradient of the dust-to-gas mass ratio for all galaxies observed by HeViCS whose metallicity gradients are available in the literature. They are all late type Sbc galaxies, namely NGC 4254, NGC 4303, NGC 4321, and NGC 4501. Methods. We fitted PACS and SPIRE observations with a single-temperature modified blackbody, inferred the dust mass, and calculated two dimensional maps of the dust-to-gas mass ratio, with the total mass of gas from available HI and CO maps. HI moment-1 maps were used to derive the geometric parameters of the galaxies and extract the radial profiles. We examined different dependencies on metallicity of the CO-to-H 2 conversion factor (XCO), used to transform the 12CO observations into the amount of molecular hydrogen. Results. We found that in these galaxies the dust-to-gas mass ratio radial profile is extremely sensitive to choice of the XCO value, since the molecular gas is the dominant component in the inner parts. We found that for three galaxies of our sample, namely NGC 4254, NGC 4321, and NGC 4501, the slopes of the oxygen and of the dust-to-gas radial gradients agree up to ~0.6-0.7 R 25 using XCO values in the range 1/3-1/2 Galactic X CO. For NGC 4303 a lower value of XCO ~ 0.1 × 1020 is necessary. Conclusions. We suggest that such low X CO values might be due to a metallicity dependence of XCO (from close to linear for NGC 4254, NGC 4321, and NGC 4501 to superlinear for NGC 4303), especially in the radial regions RG < 0.6-0.7 R 25 where the molecular gas dominates. On the other hand, the outer regions, where the atomic gas component is dominant, are less affected by the choice of XCO, and thus we cannot put constraints on its value there. © 2011 ESO.
Filiaciones:
Magrini L.:
INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi, 5, 50125 Firenze, Italy
Bianchi S.:
INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi, 5, 50125 Firenze, Italy
Corbelli E.:
INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi, 5, 50125 Firenze, Italy
Cortese L.:
European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei Munchen, Germany
Hunt L.:
INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi, 5, 50125 Firenze, Italy
Smith M.:
Department of Physics and Astronomy, Cardiff University, Parade Cardiff, CF24 3AA, United Kingdom
Vlahakis C.:
Departamento de Astronomia, Universidad de Chile, Casilla 36-D, Santiago, Chile
Davies J.:
Department of Physics and Astronomy, Cardiff University, Parade Cardiff, CF24 3AA, United Kingdom
Bendo G.J.:
Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, United Kingdom
Baes M.:
Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281 S9, 9000 Gent, Belgium
Boselli A.:
Laboratoire d'Astrophysique de Marseille, UMR 6110 CNRS, 38 rue F. Joliot-Curie, 13388 Marseille, France
Clemens M.:
Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio 5, 35122 Padova, Italy
Casasola V.:
INAF, Istituto di Radioastronomia, Via P. Gobetti 101, 40129 Bologna, Italy
De Looze I.:
Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281 S9, 9000 Gent, Belgium
Fritz J.:
Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281 S9, 9000 Gent, Belgium
Giovanardi C.:
INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi, 5, 50125 Firenze, Italy
Grossi M.:
CAAUL, Observatorio Astronomico de Lisboa, Universidade de Lisboa, Tapada de Ajuda, 1349-018 Lisboa, Portugal
Hughes T.:
Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871, China
Madden S.:
Service d'Astrophysique, CEA/Saclay, l'Orme des Merisiers, 91191 Gif-sur-Yvette, France
Pappalardo C.:
INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi, 5, 50125 Firenze, Italy
Pohlen M.:
Department of Physics and Astronomy, Cardiff University, Parade Cardiff, CF24 3AA, United Kingdom
Di Serego Alighieri S.:
INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi, 5, 50125 Firenze, Italy
Verstappen J.:
Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281 S9, 9000 Gent, Belgium
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