The Initial Mass Function of the Galactic Bulge down to ∼0.15<i>M</i><sub>⊙</sub>

Zoccali, M.; Cassisi, S.; Frogel, J. A.; Gould, Andrew; Ortolani, S.; Renzini, A.; Rich, R. Michael; Stephens, Andrew W.

doi:10.1086/308359

Cited by 169 publications

(197 citation statements)

References 39 publications

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“…The studies of the IMF by Kroupa et al (1993) and Zoccali et al (2000) support this IMF. Alternatively, we also consider the IMF of Scalo (1986, S86),…”

Section: Binary Population Synthesismentioning

confidence: 72%

Producing Type Iax supernovae from a specific class of helium-ignited WD explosions

Wang

Justham

Han

2013

A&A

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Context. It has recently been proposed that one subclass of Type Ia supernovae (SNe Ia) is sufficiently distinct and sufficiently common to be classified separately from the bulk of SNe Ia; the suggested class name is Type Iax supernovae (SNe Iax), after SN 2002cx. However, their progenitors are still uncertain. Aims. We study whether the population properties of this class might be understood if the events originate from a subset of subChandrasekhar mass explosions. In this potential progenitor population, a carbon-oxygen white dwarf (CO WD) accumulates a helium layer from a non-degenerate helium star; ignition of that helium layer then leads to ignition of the CO WD. Methods. We incorporated detailed binary evolution calculations for the progenitor systems into a binary population synthesis model to obtain rates and delay times for these events. Results. The predicted Galactic event rate of these explosions is ∼1.5 × 10 −3 yr −1 according to our standard model, in good agreement with the measured rates of SNe Iax. In addition, predicted delay times are ∼70 Myr−800 Myr, consistent with the fact that most of SNe Iax have been discovered in late-type galaxies. If the explosions are assumed to be double detonations -following current model expectations -then, based on the CO WD masses at explosion, we also estimate the distribution of resulting SN brightness (−13 > ∼ M bol > ∼ −19 mag), which can reproduce the empirical diversity of SNe Iax. Conclusions. We speculate on why binaries with non-degenerate donor stars might lead to SNe Iax if similar systems with degenerate donors do not. We suggest that the high mass of the helium layer necessary for ignition at the lower accretion rates typically delivered from non-degenerate donors might be necessary to produce SN 2002cx-like characteristics, perhaps even by changing the nature of the CO ignition.

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“…The studies of the IMF by Kroupa et al (1993) and Zoccali et al (2000) support this IMF. Alternatively, we also consider the IMF of Scalo (1986, S86),…”

Section: Binary Population Synthesismentioning

confidence: 72%

Producing Type Iax supernovae from a specific class of helium-ignited WD explosions

Wang

Justham

Han

2013

A&A

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“…This IMF is based on Salpeter's mass function for the more massive stars (Salpeter 1955); i.e., dN=dM / m À with ¼ À2:35. For lower masses, the IMF is flatter, as determined from bulge star counts at 6 projected distance from the GC (Zoccali et al 2000; exponent À2.0 for 1 M > M > 0:7M and À1.65 for M < 0:7M ). For the lowest masses, there is a correction to the exponent due to binaries (Miralda-Escudé & Gould 2000).…”

Section: Model Parametersmentioning

confidence: 95%

Really Cool Stars and the Star Formation History at the Galactic Center

Blum

Ramírez

Sellgren

et al. 2003

ApJ

131

248

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We present =D ¼ 550-1200 near-infrared H and K spectra for a magnitude-limited sample of 79 asymptotic giant branch and cool supergiant stars in the central %5 pc (diameter) of the Galaxy. We use a set of similar spectra obtained for solar neighborhood stars with known T eff and M bol that is in the same range as the Galactic center (GC) sample to derive T eff and M bol for the GC sample. We then construct the H-R diagram for the GC sample. Using an automated maximum likelihood routine, we derive a coarse star formation history of the GC. We find that (1) roughly 75% of the stars formed in the central few parsecs are older than 5 Gyr; (2) the star formation rate (SFR) is variable over time, with a roughly 4 times higher SFR in the last 100 Myr compared to the average SFR; (3) our model can match dynamical limits on the total mass of stars formed only by limiting the initial mass function to masses above 0.7 M (this could be a signature of mass segregation or of the bias toward massive star formation from the unique star formation conditions in the GC); (4) blue supergiants account for 12% of the total sample observed, and the ratio of red to blue supergiants is roughly 1.5; and (5) models with isochrones with ½Fe=H ¼ 0:0 over all ages fit the stars in our H-R diagram better than models with lower [Fe/H]

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“…For instance, an index α = 1.35 would produce ∼20% less events. A flat mass function at the low mass end seems to be favored by the luminosity function towards the Bulge (Holtzman et al 1998;Zoccali et al 2000). However there remains uncertainties in the binaries fraction, and also a flat mass function would be in conflict with the distribution of time-scales of observed microlensing events towards the Galactic Centre.…”

Section: Lens Mass Functionmentioning

confidence: 98%

The Sagittarius dwarf galaxy as a microlensing target

Cseresnjes¹,

Alard²

2001

A&A

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Abstract. We estimate the optical depth, time-scale distribution and fraction of microlensing events originating from sources in the Sagittarius dwarf galaxy (Sgr) lensed by deflectors in the Milky Way. These events have a time-scale longer by a factor ∼1.3 than the MW/MW events and occur mainly on sources fainter than V ∼ 21 mag below Sgr's turn off. The fraction of events involving a source in Sgr depends on the location and extinction of the field and on the limiting magnitude of the survey. The contribution of the MW/Sgr events is negligible ( < ∼ 1%) at very low latitudes (|b| < ∼ 2 • ) but increases continuously towards higher |b| and becomes dominant near the highest density region of the dwarf galaxy. Sgr is present within the fields of current microlensing surveys and any optical depth map inferred from observations will become biased by the presence of Sgr towards higher |b| where the contribution of MW/Sgr events is significant. Systematic spectroscopic measurements on the sources of all the microlensing events may allow detection of this kind of event for which the degeneracy on the lens mass can be significantly reduced.

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The Initial Mass Function of the Galactic Bulge down to ∼0.15M_⊙

Cited by 169 publications

References 39 publications

Producing Type Iax supernovae from a specific class of helium-ignited WD explosions

Producing Type Iax supernovae from a specific class of helium-ignited WD explosions

Really Cool Stars and the Star Formation History at the Galactic Center

The Sagittarius dwarf galaxy as a microlensing target

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The Initial Mass Function of the Galactic Bulge down to ∼0.15M⊙

Cited by 169 publications

References 39 publications

Producing Type Iax supernovae from a specific class of helium-ignited WD explosions

Producing Type Iax supernovae from a specific class of helium-ignited WD explosions

Really Cool Stars and the Star Formation History at the Galactic Center

The Sagittarius dwarf galaxy as a microlensing target

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Product

Resources

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The Initial Mass Function of the Galactic Bulge down to ∼0.15M_⊙