A Color-Magnitude Diagram in Field #3 of the Palomar—Groningen Survey

Ng, Y. K.; Bertelli, G.; Bressan, A.; Chiosi, C.

doi:10.1007/978-94-011-2434-8_129

Cited by 7 publications

(7 citation statements)

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“…They applied this method to the OGLE‐I data and then found the ratio of total to selective extinction R VI ≡ A V / E ( V − I ) = 2.44. This is consistent with Ng et al (1996). Stanek (1996) applied this method to the OGLE‐I data to obtain differential extinction A V and reddening E ( V − I ) in a 40 × 40 arcmin 2 region of Baade's window, with a resolution of ∼30 arcsec.…”

Section: Introductionsupporting

confidence: 63%

“…Schultheis et al (1999) and Dutra et al (2003) constructed K ‐band extinction maps of the Galactic central region with a resolution of 4 arcmin by using J and K photometry of the upper giant branch stars in Deep Near Infrared Survey (DENIS) and Two‐Micron All‐Sky Survey (2MASS) data, respectively. Some determinations of the extinction towards Baade's window have been performed with a number of different techniques, including those of stellar simulation (Ng et al 1996), mean magnitudes of red clump stars (Kiraga, Paczyński & Stanek 1997), the absolute magnitude of RR Lyrae stars (Alcock et al 1998b) and magnitude of the K‐giants (Gould, Popowski & Terndrup 1998). The large‐scale extinction map of the GB was made by using the mean colour of all stars in the MACHO project photometry (Popowski, Cook & Becker 2003b).…”

Section: Introductionmentioning

confidence: 99%

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Extinction map of the Galactic centre: OGLE-II Galactic bulge fields

Sumi

2004

Monthly Notices of the Royal Astronomical Society

120

207

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We present the reddening [E(V−I)] and extinction maps in the V band (AV) and the I band (AI) for 48 Optical Gravitational Lensing Experiment II (OGLE‐II) Galactic bulge (GB) fields, covering a range of −11° < l < 11°, with the total area close to 11 deg2. These measurements are based on two‐band photometry of red clump giant (RCG) stars in OGLE‐II VI maps of the GB. We confirm the anomalous value of the ratio of total to selective extinction RVI≡AV/E(V−I) = 1.9–2.1, depending on the line of sight, as measured recently by Udalski. By using the average value of RVI= 1.964 with the standard deviation sdev= 0.085, we measured E(V−I), AV and AI, and we obtained extinction and reddening maps with a high spatial resolution of 26.7–106.8 arcsec, depending on the stellar density of each field. We have assumed that average, reddening corrected colours of RCGs are the same in every field. The maps cover the ranges 0.42 < E(V−I) < 3.5, 0.83 < AV < 6.9 and 0.41 < AI < 3.4 mag, respectively. The zero‐points of these maps are calibrated by using V−K colours of 20 RR Lyrae ab variables (RRab) in Baade's window. The apparent reddening corrected I‐band magnitudes of the RCGs change by +0.4 mag while the Galactic coordinate l varies from +5° to −5°, indicating that these stars are in the Galactic bar. The reddening corrected colour of RRab and RCGs in the GB are consistent with colours of local stars, while in the past these colours were claimed to be different.

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Section: Introductionsupporting

confidence: 63%

Section: Introductionmentioning

confidence: 99%

Extinction map of the Galactic centre: OGLE-II Galactic bulge fields

Sumi

2004

Monthly Notices of the Royal Astronomical Society

120

207

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“… References : fl =Flynn et al (2006); o =Ojha (2001); fe =Feast (2000); k =Kuijken & Gilmore (1989b); n =Ng et al (1997); s =Spagna et al (1996); d =Dehnen & Binney (1998); x =Xue et al (2008); and g =Guo et al (2010). …”

Section: Testing the Methodsmentioning

confidence: 99%

Limits on the local dark matter density

Garbari

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Lake

2011

Monthly Notices of the Royal Astronomical Society

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We revisit systematics in determining the local dark matter density (rho_dm) from the vertical motion of stars in the Solar Neighbourhood. Using a simulation of a Milky Way-like galaxy, we determine the data-quality required to detect the dark matter density at its expected local value. We introduce a new method for recovering rho_dm that uses moments of the Jeans equations, combined with a Monte Carlo Markov Chain technique to marginalise over the unknown parameters. Given sufficiently good data, we show that our method can recover the correct local dark matter density even in the face of disc inhomogeneities, non-isothermal tracers and a non-separable distribution function. We illustrate the power of our technique by applying it to Hipparcos data [Holmberg & Flynn 2000,2004]. We first make the assumption that the A and F star tracer populations are isothermal. This recovers rho_dm=0.003^{+0.009}_{-0.007}Msun/pc^3 (with 90 per cent confidence), consistent with previous determinations. However, the vertical dispersion profile of these tracers is poorly known. If we assume instead a non-isothermal profile similar to the blue disc stars from SDSS DR-7 [Abazajian et al. 2009] measured by Bond et al. (2009), we obtain a fit with a very similar chi^2 value, but with rho_dm=0.033^{+0.008}_{-0.009}Msun/pc^3 (with 90 per cent confidence). This highlights that it is vital to measure the vertical dispersion profile of the tracers to recover an unbiased estimate of the local dark matter density.Comment: 25 pages, 21 figures; accepted for publication in MNRA

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“…Whereas there are some indications for the presence of intermediate‐mass stars (see Rich 1999 for a review), studies of Baade's Window population (e.g. Frogel 1988; Holtzman et al 1993; Ortolani et al 1995; Ng et al 1996) generally indicate that the bulk of star formation occurred at old ages. Only the very central regions of the bulge show unequivocal evidences of recent star formation (e.g.…”

Section: The Clump In Other Galaxy Systemsmentioning

confidence: 99%

Population effects on the red giant clump absolute magnitude, and distance determinations to nearby galaxies

Girardi

Salaris

2001

Monthly Notices of the Royal Astronomical Society

265

346

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The red giant clump has been recently argued to be a reliable distance indicator for the galaxies in the Local Group. The accuracy of distance determinations based on this method, however, depends on the possible presence of systematic magnitude differences (ΔMIRC) between the local clump revealed by the Hipparcos colour–magnitude diagram (CMD), and the clump stars observed in distant galaxies. In this paper, we re‐address the problem of these systematic ‘population’ effects. First, we present tables with the theoretically predicted I‐band clump magnitude as a function of age and metallicity. Simple equations, taken from basic population synthesis theory, are provided for the easy computation of the mean clump magnitude for any given galaxy model. We use our models to explain in some detail what determines the distribution of masses, ages and metallicities of clump stars in a galaxy. Such an approach has so far been neglected in the analysis of clump data related with distance determinations. We point out that, in galaxies with recent/ongoing star formation (e.g. the discs of spirals), the age distribution of clump stars is strongly biased towards younger (∼1–3 Gyr) ages, and hence towards higher metallicities. Obviously, this does not happen in galaxies with predominantly old stellar populations (e.g. ellipticals and bulges). We construct detailed models for the clump population in the local (Hipparcos) sample, the bulge, Magellanic Clouds and Carina dSph galaxy. In all cases, star formation rates and chemical enrichment histories are taken from the literature. The Hipparcos model is shown to produce distributions of metallicities, colours, and magnitudes, that are similar to those derived from spectroscopic and Hipparcos data. The bulge, Magellanic Clouds, and Carina dSph models are used to analyse the values of ΔMIRC for these different stellar systems. We show how the clump–RR Lyrae data from Udalski are well reproduced by the models. However, despite the similarity between the models and data, the models indicate that the linear ΔMIRC versus [Fe/H] relations that have been derived from the same data (such as by Udalski and Popowski) are not general. In fact, the distribution of clump stars has several factors hidden in it – e.g. the age–metallicity relation, the rate of past star formation – that cannot be described by such relations. The model behaviour is also supported by empirical data for open clusters by Sarajedini and Twarog et al. We argue that Udalski's data for Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC) star clusters do not allow a good assessment of the age dependence of the clump magnitude. Moreover, we remark that similar analyses of cluster data should better include clump stars with ages 1–2 Gyr, which turn out to be very important in determining the mean clump in galaxies with recent star formation. Finally, we provide revised clump distances to the bulge, Magellanic Clouds and Carina dSph, and further comment on their reliability. The largest ΔMIRC values are found for the...

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A Color-Magnitude Diagram in Field #3 of the Palomar—Groningen Survey

Cited by 7 publications

References 0 publications

Extinction map of the Galactic centre: OGLE-II Galactic bulge fields

Extinction map of the Galactic centre: OGLE-II Galactic bulge fields

Limits on the local dark matter density

Population effects on the red giant clump absolute magnitude, and distance determinations to nearby galaxies

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