Monte Carlo simulations of the halo white dwarf population

Abstract

Abstract. The interpretation of microlensing results towards the Large Magellanic Cloud (LMC) still remains controversial. While white dwarfs have been proposed to explain these results and, hence, to contribute significantly to the mass budget of our Galaxy, there are also several constraints on the role played by white dwarfs. In this paper we analyze self-consistently and simultaneously four different results, namely, the local halo white dwarf luminosity function, the microlensing results reported by the MACHO team towards the LMC, the results of Hubble Deep Field (HDF) and the results of the EROS experiment, for several initial mass functions and halo ages. We find that the proposed log-normal initial mass functions do not contribute to solve the problem posed by the observed microlensing events and, moreover, they overproduce white dwarfs when compared to the results of the HDF and of the EROS survey. We also find that the contribution of hydrogen-rich white dwarfs to the dynamical mass of the halo of the Galaxy cannot be more than ∼4%.

Testing the Initial–Final Mass Relationship of White Dwarfs

“…(6.6) can be easily solved. Taking into account the luminosity functions obtained in García-Berro & Torres (1997), García-Berro et al (1999) and Isern et al (1998), García-Berro et al (2004) for the disk and the halo populations, respectively, the number of white dwarfs for each of the Alhambra fields -see Fig. 6.1 -can be obtained.…”

“…This means that these objects have imprinted a memory of the various episodes that the Galaxy has been subject to over its history, constituting useful objects to probe its structure and evolution. Moreover, it is thought that white dwarfs could also contribute significantly to the baryonic dark matter (García-Berro et al 2004). For all these reasons, it is essential to improve our knowledge about the white dwarf population from all the possible points of view.…”

“…Finally, we have estimated the number of white dwarfs that might be found in the Alhambra Survey. Taking into account the luminosity functions obtained in García-Berro & Torres (1997), García-Berro et al (1999) and Isern et al (1998), García-Berro et al (2004) for the disk and the halo populations, respectively, we consider that a total of 300 white dwarfs are expected to be detected in the Alhambra survey. It is worth to emphasize the relevance of this number, since the actual number of spectroscopically identified white dwarfs is of the order of 2500.…”

White dwarfs with hydrogen-deficient atmospheres and the dark matter content of the Galaxy

“…A detailed description of our Monte Carlo simulator has been already presented in García-Berro et al (1999), García-Berro et al (2004), Camacho et al (2007) and Torres et al (2002). Consequently, we will only summarize the most important inputs here.…”

“…In a series of previous papers we have exhaustively analyzed the contributions of the halo populations of carbon-oxygen (CO) and oxygen-neon (ONe) white dwarfs with pure hydrogen atmospheres (García-Berro et al 2004;Camacho et al 2007). We have also extended our previous studies to include the population of halo red dwarfs (Torres et al 2008).…”