Journal
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Volume 428, Issue 4, Pages 3183-3195Publisher
OXFORD UNIV PRESS
DOI: 10.1093/mnras/sts262
Keywords
stars: luminosity function, mass function; galaxies: bulges; galaxies: kinematics and dynamics; galaxies: spiral; dark matter
Categories
Funding
- National Science Foundation Science and Technology Center CfAO [AST-9876783]
- HST grants [GO-12292, GO-11978, GO-11202, GO-11206.02-A]
- NSF through CAREER award [NSF-0642621]
- Packard Foundation through a Packard Research Fellowship
- Royal Society
- Department of Energy [DE-AC02-76SF00515]
- NSF [AST-0808133]
- NWO-VIDI programme [639.042.505]
- NASA through Hubble Space Telescope programmes [GO-10587, GO-10886, GO-10174, 10494, 10798, 11202, 11978, 12292]
- National Science Foundation [PHY99-07949]
- NASA [NAS 5-26555]
- W.M. Keck Foundation
- Alfred P. Sloan Foundation
- National Science Foundation
- US Department of Energy
- National Aeronautics and Space Administration
- Japanese Monbukagakusho
- Max Planck Society
- Higher Education Funding Council for England
- Direct For Mathematical & Physical Scien [808133] Funding Source: National Science Foundation
- Division Of Astronomical Sciences [808133] Funding Source: National Science Foundation
- Division Of Astronomical Sciences
- Direct For Mathematical & Physical Scien [807458] Funding Source: National Science Foundation
- STFC [ST/J001538/1] Funding Source: UKRI
- Science and Technology Facilities Council [ST/H00243X/1, ST/J001538/1] Funding Source: researchfish
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Recent work has suggested that the stellar initial mass function (IMF) is not universal, but rather is correlated with galaxy stellar mass, stellar velocity dispersion or morphological type. In this paper, we investigate variations of the IMF within individual galaxies. For this purpose, we use strong lensing and gas kinematics to measure independently the normalization of the IMF of the bulge and disc components of a sample of five massive spiral galaxies with substantial bulge components taken from the Sloan WFC Edge-on Late-type Lens Survey (SWELLS). We find that the stellar masses of the bulges are tightly constrained by the lensing and kinematic data. A comparison with masses based on stellar population synthesis models fitted to optical and near-infrared photometry favours a Salpeter-like normalization of the IMF. Conversely, the disc masses are less well constrained due to degeneracies with the dark matter halo, but are consistent with Milky Way-type IMFs in agreement with previous studies. The discs are submaximal at 2.2 disc scale lengths, but due to the contribution of the bulges, the galaxies are baryon dominated at 2.2 disc scale lengths. Globally, our inferred IMF normalization is consistent with that found for early-type galaxies of comparable stellar mass (>10(11) M-circle dot). Our results suggest a non-universal IMF within the different components of spiral galaxies, adding to the well-known differences in stellar populations between discs and bulges.
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