Possible M dwarf enrichment in the semistellar nucleus of M31

Faber, S. M.; French, H. B.

doi:10.1086/157644

Cited by 166 publications

(224 citation statements)

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“…Further observations by many groups (see e.g. Whitford 1977;Frogel et al 1978;Cohen 1978;Faber & French 1980;Carter, Visvanathan & Pickles 1986;Alloin & Bica 1989;Delisle & Hardy 1992) have led to conflicting results. Conroy & van Dokkum (2012b) observed the central 15 pc of M31 (4 ) and inferred a mass-to-light ratio consistent with an IMF slope between Chabrier and Salpeter.…”

Section: Discussionmentioning

confidence: 99%

“…Throughout the second half of the 20th century, several papers highlighted and detected specific stellar absorption features that are prominent in the spectra of low mass stars, but absent in high mass counterparts (e.g. Wing-Ford band FeH λ9916: Wing & Ford 1969, Schiavon, Barbuy & Singh 1997, Cushing et al 2003; sodium NaI λ8190: Faber & French 1980. A lack of both high signalto-noise and detailed stellar populations models, coupled with the challenges of spectroscopy in the far red and nearinfrared, meant that arguments for a varying IMF were inconclusive.…”

Section: Introductionmentioning

confidence: 99%

“…The core has been known to have prominent sodium absorption and this has been interpreted as an increased dwarf abundance by some (e.g. Faber & French 1980) and sodium enhancement by others (e.g. Alloin & Bica 1989).…”

Section: Introductionmentioning

confidence: 99%

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The initial mass functions of M31 and M32 through far red stellar absorption features

Zieleniewski

Houghton

Thatte

et al. 2015

Mon. Not. R. Astron. Soc.

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Using the Oxford Short Wavelength Integral Field specTrograph, 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 λ8190 index shows a flat equivalent width profile at ∼ 0.4Å through the majority of the bulge, with a strong gradient up to 0.8Å in the central 10 (38 pc); the Wing-Ford FeH λ9916 index is measured to be constant at 0.4Å for all radii; and calcium triplet CaT λ8498, 8542, 8662 shows a gradual increase through the bulge towards the centre. M32 displays flat profiles for all three indices, with FeH at ∼ 0.5Å, very high CaT at ∼ 0.8Å and low NaI at ∼ 0.1Å. 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 [α/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.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The initial mass functions of M31 and M32 through far red stellar absorption features

Zieleniewski

Houghton

Thatte

et al. 2015

Mon. Not. R. Astron. Soc.

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“…The debate centered on whether this enhancement is due primarily to an increase in the dwarf star contribution or an increase in the [Na/Fe] abundance. If interpreted as the former, the implied mass-to-light ratio would be M/L B ≈ 28 (Faber & French 1980), which would be in strong conflict with dynamical constraints (Saglia et al 2010). Note that while the best-fit models are offset low compared to the data, the trend of CaT strength with the inferred IMF is similar between the models and the data.…”

Section: The Nuclear Bulge Of M31mentioning

confidence: 92%

The Stellar Initial Mass Function in Early-Type Galaxies From Absorption Line Spectroscopy. Ii. Results

Conroy

Dokkum

2012

ApJ

506

571

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The spectral absorption lines in early-type galaxies contain a wealth of information regarding the detailed abundance pattern, star formation history, and stellar initial mass function (IMF) of the underlying stellar population. Using our new population synthesis model that accounts for the effect of variable abundance ratios of 11 elements, we analyze very high quality absorption line spectra of 38 early-type galaxies and the nuclear bulge of M31. These data extend to 1 μm and they therefore include the IMF-sensitive spectral features Na i, Ca ii, and FeH at 0.82 μm, 0.86 μm, and 0.99 μm, respectively. The models fit the data well, with typical rms residuals 1%. Strong constraints on the IMF and therefore the stellar mass-to-light ratio, (M/L) stars , are derived for individual galaxies. We find that the IMF becomes increasingly bottom-heavy with increasing velocity dispersion and [Mg/Fe]. At the lowest dispersions and [Mg/Fe] values the derived IMF is consistent with the Milky Way (MW) IMF, while at the highest dispersions and [Mg/Fe] values the derived IMF contains more low-mass stars (is more bottom-heavy) than even a Salpeter IMF. Our best-fit (M/L) stars values do not exceed dynamically based M/L values. We also apply our models to stacked spectra of four metal-rich globular clusters in M31 and find an (M/L) stars that implies fewer low-mass stars than a MW IMF, again agreeing with dynamical constraints. We discuss other possible explanations for the observed trends and conclude that variation in the IMF is the simplest and most plausible.

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“…To illustrate possibilities for studying the process of star formation in infrared-luminous galactic nuclei, I will describe and expand on a recent study of M82 (Rieke et al-1980)Given the continuing controversy over the stellar content of a well-behaved nucleus like that of M31 (Faber and French 1980;Persson et al 1980), it may seem surprising that much of use can be deduced about the content of M82. However, conditions in the latter galaxy are sufficiently extreme to compensate for our inability to observe some of the traditional indicators of stellar content.…”

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confidence: 99%

Rapid Star Formation in Galactic Nuclei

Rieke

1981

Symp. - Int. Astron. Union

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A large percentage of spiral galaxies are forming stars at a very high rate in their nuclei. There are indications that the process of star formation is modified significantly in these regions, compared with the solar neighborhood.The star formation may be fueled by interstellar material that is captured by the nucleus. Further work is needed to explore these possibilities and to establish the evolutionary connections among galactic nuclei, various types of which can be distinguished by their radically different infrared properties.

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Possible M dwarf enrichment in the semistellar nucleus of M31

Cited by 166 publications

References 0 publications

The initial mass functions of M31 and M32 through far red stellar absorption features

The initial mass functions of M31 and M32 through far red stellar absorption features

The Stellar Initial Mass Function in Early-Type Galaxies From Absorption Line Spectroscopy. Ii. Results

Rapid Star Formation in Galactic Nuclei

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