Mild radial variations of the stellar IMF in the bulge of M31
Using new, homogeneous, long-slit spectroscopy in the wavelength range from ∼0.35 to ∼1 μm, we study radial gradients of optical and near-infrared (NIR) initial mass function (IMF)-sensitive features along the major axis of the bulge of M31, out to a galactocentric distance of ∼200 arcsec (∼800 pc)....
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| Main Authors: | , , , |
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| Format: | Article (Journal) |
| Language: | English |
| Published: |
2021 May 26
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| In: |
Monthly notices of the Royal Astronomical Society
Year: 2021, Volume: 505, Issue: 1, Pages: 415-434 |
| ISSN: | 1365-2966 |
| DOI: | 10.1093/mnras/stab1136 |
| Online Access: | Verlag, lizenzpflichtig, Volltext: https://doi.org/10.1093/mnras/stab1136 Verlag, lizenzpflichtig, Volltext: https://academic.oup.com/mnras/article/505/1/415/6253217 
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| Author Notes: | F. La Barbera, A. Vazdekis, I. Ferreras and A. Pasquali |
| Summary: | Using new, homogeneous, long-slit spectroscopy in the wavelength range from ∼0.35 to ∼1 μm, we study radial gradients of optical and near-infrared (NIR) initial mass function (IMF)-sensitive features along the major axis of the bulge of M31, out to a galactocentric distance of ∼200 arcsec (∼800 pc). Based on state-of-the-art stellar population synthesis models with varying Na abundance ratio, we fit a number of spectral indices, from different chemical species (including TiO’s, Ca, and Na indices), to constrain the low-mass (≲0.5 M⊙) end slope (i.e. the fraction of low-mass stars) of the stellar IMF, as a function of galactocentric distance. Outside a radial distance of ∼10 arcsec, we infer an IMF similar to a Milky Way-like distribution, while at small galactocentric distances, an IMF radial gradient is detected, with a mildly bottom-heavy IMF in the few inner arcsec. We are able to fit Na features (both NaD and Na I8190), without requiring extremely high Na abundance ratios. [Na/Fe] is ∼0.4 dex for most of the bulge, rising up to ∼0.6 dex in the innermost radial bins. Our results imply an overall, luminosity-weighted, IMF and mass-to-light ratio for the M31 bulge, consistent with those for a Milky Way-like distribution, in contrast to results obtained, in general, for most massive early-type galaxies. |
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| Item Description: | Gesehen am 17.09.2021 |
| Physical Description: | Online Resource |
| ISSN: | 1365-2966 |
| DOI: | 10.1093/mnras/stab1136 |