%0 Generic %1 zieleniewski2015initial %A Zieleniewski, Simon %A Houghton, Ryan C. W. %A Thatte, Niranjan %A Davies, Roger L. %D 2015 %K absorption imf lines variation %T The initial mass functions of M31 and M32 through far red stellar absorption features %U http://arxiv.org/abs/1506.02654 %X Using the Oxford Short Wavelength Integral Field specTrograph (SWIFT), we investigate radial variations of several initial mass function (IMF) dependent absorption features in M31 and M32. We obtain high signal-to-noise spectra at six pointings along the major axis of M31 out to ~ 700'' (2.7 kpc) and a single pointing of the central 10 pc for M32. In M31 the sodium NaI łambda8190 index shows a flat equivalent width profile at ~ 0.4 \AA through the majority of the bulge, with a strong gradient up to 0.8 \AA in the central 10'' (38 pc); the Wing-Ford FeH łambda9916 index is measured to be constant at 0.4 \AA for all radii; and calcium triplet CaT łambda8498, 8542, 8662 shows a gradual increase through the bulge towards the centre. M32 displays flat profiles for all three indices, with FeH at ~ 0.5 \AA, very high CaT at ~ 0.8 \AA and low NaI at ~ 0.1 \AA. We analyse these data using stellar population models. We find that M31 is well described on all scales by a Chabrier IMF, with a gradient in sodium enhancement of Na/Fe ~ +0.3 dex in the outer bulge, rising within the central 10'' to perhaps Na/Fe ~ +1.0 dex in the nuclear region. We find M32 is described by a Chabrier IMF and young stellar age in line with other studies. Models show that CaT is much more sensitive to metallicity and \alpha/Fe than to IMF. We note that the centres of M31 and M32 have very high stellar densities and yet we measure Chabrier IMFs in these regions.

@misc{zieleniewski2015initial, abstract = {Using the Oxford Short Wavelength Integral Field specTrograph (SWIFT), we investigate radial variations of several initial mass function (IMF) dependent absorption features in M31 and M32. We obtain high signal-to-noise spectra at six pointings along the major axis of M31 out to ~ 700'' (2.7 kpc) and a single pointing of the central 10 pc for M32. In M31 the sodium NaI {\lambda}8190 index shows a flat equivalent width profile at ~ 0.4 {\AA} through the majority of the bulge, with a strong gradient up to 0.8 {\AA} in the central 10'' (38 pc); the Wing-Ford FeH {\lambda}9916 index is measured to be constant at 0.4 {\AA} for all radii; and calcium triplet CaT {\lambda}8498, 8542, 8662 shows a gradual increase through the bulge towards the centre. M32 displays flat profiles for all three indices, with FeH at ~ 0.5 {\AA}, very high CaT at ~ 0.8 {\AA} and low NaI at ~ 0.1 {\AA}. We analyse these data using stellar population models. We find that M31 is well described on all scales by a Chabrier IMF, with a gradient in sodium enhancement of [Na/Fe] ~ +0.3 dex in the outer bulge, rising within the central 10'' to perhaps [Na/Fe] ~ +1.0 dex in the nuclear region. We find M32 is described by a Chabrier IMF and young stellar age in line with other studies. Models show that CaT is much more sensitive to metallicity and [{\alpha}/Fe] than to IMF. We note that the centres of M31 and M32 have very high stellar densities and yet we measure Chabrier IMFs in these regions.}, added-at = {2015-06-10T06:34:51.000+0200}, author = {Zieleniewski, Simon and Houghton, Ryan C. W. and Thatte, Niranjan and Davies, Roger L.}, biburl = {https://www.bibsonomy.org/bibtex/29cd303b3ebcca83ab5c768122b162e39/miki}, description = {[1506.02654] The initial mass functions of M31 and M32 through far red stellar absorption features}, interhash = {6bc296b0f8937d834e5ba4b5a1d45ea5}, intrahash = {9cd303b3ebcca83ab5c768122b162e39}, keywords = {absorption imf lines variation}, note = {cite arxiv:1506.02654Comment: 11 pages, 9 figures, accepted for publication in MNRAS}, timestamp = {2015-06-10T06:34:51.000+0200}, title = {The initial mass functions of M31 and M32 through far red stellar absorption features}, url = {http://arxiv.org/abs/1506.02654}, year = 2015 }