Population effects on the red giant clump absolute magnitude: the<i>K</i>band

Salaris, Maurizio; Girardi, L.

doi:10.1046/j.1365-8711.2002.05917.x

Cited by 190 publications

(242 citation statements)

References 30 publications

Supporting

Mentioning

214

Contrasting

Order By: Relevance

“…According to Zoccali et al (2008), the bulge's metal content varies from [Fe/H] ∼ −0.3 at b = −12 • to [Fe/H] ∼ −0.1 at b = −4 • and there is a hint of a lack of gradients in the inner regions ). Teramo stellar evolution models indicate that a 0.2 dex variation in metallicity would affect the intrinsic magnitude of the RC by ∼0.10 mag, consistent as well with Salaris & Girardi (2002). If for a solar metallicity population at 8 kpc from the Sun we assume a main metallicity 0.20 dex lower, our method will result in measuring a distance of ∼8.2 kpc instead.…”

Section: Bulge Luminosity Function and Distancessupporting

confidence: 71%

“…(2), in the regions As discussed for the reddening calculations, the assumption of homogeneous stellar populations on the bulge are the main source of uncertainties. The intrinsic magnitude of the RC is known to have a dependence on age and metallicity (Salaris & Girardi 2002;Pietrzyński et al 2003). While the age of the bulge is expected to be homogeneously old (∼10 Gyr), the metallicity is known to change at least along the minor axis (Zoccali et al 2008).…”

Section: Bulge Luminosity Function and Distancesmentioning

confidence: 99%

“…For an old and relatively metal-rich population like the one in the Galactic bulge (e.g. Brown et al 2010, and references therein), the population corrections for red clump absolute K-band magnitude are on the order of 0.1 mag (Salaris & Girardi 2002). For this reason, photometric properties of red clump giants can be used to trace simultaneously extinction and relative distances in the bulge.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Reddening and metallicity maps of the Milky Way bulge from VVV and 2MASS

Gonzalez

Rejkuba

Zoccali

et al. 2011

A&A

134

161

View full text Add to dashboard Cite

Context. The Milky Way bulge is the nearest galactic bulge and the best laboratory for studies of stellar populations in spheroids based on individual stellar abundances and kinematics. The observed properties point to a very complex nature, which is hard to extrapolate from a few fields. Aims. We present a method of obtaining reddening maps and tracing structure and metallicity gradients of the bulge using data from the recently started ESO public survey Vista Variables in the Via Lactea (VVV). The method is used to derive properties of the fields along the minor axis. Methods. We derived the mean J − K s color of the red clump (RC) giants in 1835 subfields in the bulge region with −8 • < b < −0.4 • and 0.2 • < l < 1.7 • , and compare it to the color of RC stars in Baade's window, for which we adopt E(B − V) = 0.55. This allows us to derive the reddening map on a small enough scale to minimize the problems arising from differential extinction. The dereddened magnitudes were then used to build the bulge luminosity function in regions of ∼0.4 • × 0.4 • to obtain the mean RC magnitudes. These were used as distance indicator in order to trace the bulge structure. Finally, for each subfield the derived distance and extinction values were used to obtain photometric metallicities through interpolation of red giant branch colors on a set of empirical ridge lines. The photometric metallicity distributions were compared to metallicity distributions obtained from high-resolution spectroscopy in the same regions. Results. The reddening determination is sensitive to small-scale variations, which are clearly visible in our maps. Our results agree within the errors with literature values based on different methods, although our maps have much higher resolution and more complete coverage. The luminosity function clearly shows the double RC recently discovered in 2MASS and OGLE III datasets, thereby allowing the X-shape morphology of the bulge to be traced. Finally, the mean of the derived photometric metallicity distributions are in remarkable agreement with those obtained from spectroscopy. Conclusions. The VVV survey is a unique tool for mapping the bulge properties by means of the consistent method presented here. The remarkable agreement between our results and those presented in literature for the minor axis allows us to safely extend our method to the whole region covered by the survey.

show abstract

Section: Bulge Luminosity Function and Distancessupporting

confidence: 71%

Section: Bulge Luminosity Function and Distancesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Reddening and metallicity maps of the Milky Way bulge from VVV and 2MASS

Gonzalez

Rejkuba

Zoccali

et al. 2011

A&A

134

161

View full text Add to dashboard Cite

show abstract

“…Dependence of He abundance and contamination from AGB stars Saviane et al (2012) highlighted that the CaT method works on the assumption that V HB depends almost exclusively on [Fe/H], the other stellar parameters playing only a secondary role. While this is true for the age of old stellar systems such as GGCs (Salaris & Girardi 2002;Ferraro et al 2006), cluster-to-cluster differences in helium abundance can instead be significant, and might cause higher residuals in the calibration, if these differences are not correlated with metallicity. In general, halo GGCs share a common He abundance (Buzzoni et al 1983;Zoccali et al 2000;Cassisi et al 2003), but this might be different for BGCs.…”

Section: Metallicitiesmentioning

confidence: 99%

Deriving metallicities from calcium triplet spectroscopy in combination with near-infrared photometry

Mauro

Bidin

Geisler

et al. 2014

A&A

View full text Add to dashboard Cite

Context. When they are established with sufficient precision, the ages, metallicities and kinematics of Galactic globular clusters (GGCs) can shed much light on the dynamical and chemical evolution of the Galactic halo and bulge. While the most fundamental way of determining GC abundances is by means of high-resolution spectroscopy, in practice this method is limited to only the brighter stars in the nearest and less reddened objects. This restriction has, over the years, led to the development of a large number of techniques that measure the overall abundance indirectly from parameters that correlate with overall metallicity. One of the most efficient methods is measuring the equivalent width (EW) of the calcium II triplet (CaT) at λ ≈ 8500 Å in red giants, which are corrected for the luminosity and temperature effects using the V magnitude differences from the horizontal branch (HB). Aims. We establish a similar method in the near-infrared (NIR), by combining the power of the differential magnitudes technique with the advantages of NIR photometry to minimize differential reddening effects. Methods. We used the K s magnitude difference between the star and the reddest part of the HB (RHB) or of the red clump (RC) to generate reduced equivalent widths (rEW) from previously presented datasets. Then we calibrated these rEW against three previously reported different metallicity scales; one of which we corrected using high-resolution spectroscopic metallicities. Results. We calculated the calibration relations for the two datasets and the three metallicity scales and found that they are approximately equivalent, with almost negligible differences. We compared our NIR calibrations with the corresponding optical ones, and found them to be equivalent, which shows that the luminosity-corrected rEW using the K s magnitude is compatible with the one obtained from the V magnitude. We then used the metallicities obtained from the calibration to investigate the internal metallicity distributions of the GCs. Conclusions. We have established that the ([Fe/H]:rEW) relation is independent of the magnitude used for the luminosity correction and find that the calibration relations change only slightly for different metallicity scales. The CaT technique using NIR photometry is thus a powerful tool to derive metallicities. In particular, it can be used to study the internal metallicity spread of a GC. We confirm the presence of at least two metallicity populations in NGC 6656 and find that several other GCs present peculiar metallicity distributions.

show abstract

“…To calculate the distance a correction for population effects has to be applied (Gullieuszik et al 2007), because of the differences in the stellar content of LMC red clump stars and the Galactic red clumps on which the Alves (2000) calibration is based. Salaris & Girardi (2002) estimated the population effects on the RC absolute magnitude in the K band of ΔM RC K = −0.03. The mean distance value is (m − M) 0 = 18.46 ± 0.07.…”

Section: Period-[fe/h] Relationsmentioning

confidence: 99%

Properties of RR Lyrae stars in the inner regions of the Large Magellanic Cloud

Borissova¹,

Rejkuba²,

Minniti

et al. 2009

A&A

View full text Add to dashboard Cite

Context. RR Lyrae variable stars are the primary Population II distance indicator. Likewise, the Large Magellanic Cloud (LMC) constitutes a key step in the extragalactic distance scale. Aims. By combining near-IR photometry and spectroscopically measured metallicities for a homogeneous sample of 50 RR Lyr stars in the LMC, we investigate the metallicity dependence of the period-luminosity relation in the near-infrared (IR), use the newly derived relations to re-derive the distance to the LMC, and compare the distance moduli obtained from RR Lyr and red clump stars. Methods. This paper presents new (single-epoch) J-band and (multi-epoch) K s -band photometry of RR Lyr stars in 7 different LMC fields, observed with the near-IR camera SOFI at ESO's New Technology Telescope. Additional K s -band data for another two LMC fields were taken with the ISPI infrared array at CTIO's Blanco 4m telescope. The near-IR photometry was cross-correlated with the MACHO and OGLE databases, resulting in a catalog of 62 RR Lyr stars with BVRI JK s photometry. A subsample of 50 stars also has spectroscopically measured metallicities. Results. In the deep JK color-magnitude diagrams of 7 fields, red giant branch, red clump and RR Lyr stars are detected. The majority of RR Lyr stars are located within the instability strip with near-IR colors between 0.14 ≤ (J − K s ) 0 < 0.32. The period-luminosity relation only has a very mild dependence on metallicity in the K band, consistent with no dependence: M Ks = 2.11(±0.17) log P + 0.05(±0.07) [Fe/H] − 1.05. In the J band the currently available data do not allow firm conclusions regarding the metallicity dependence of the period-luminosity relation. Conclusions. The distance modulus of the LMC, derived using our near-IR period-luminosity-metallicity relation for RR Lyr stars, is (m − M) 0 = 18.53 ± 0.13, in very good agreement with the distance modulus from the red clump stars, 18.46 ± 0.07. However, LMC modulus derived from the RR Lyrae stars depends on the parallax of the star RR Lyrae.

show abstract

Population effects on the red giant clump absolute magnitude: theKband

Cited by 190 publications

References 30 publications

Reddening and metallicity maps of the Milky Way bulge from VVV and 2MASS

Reddening and metallicity maps of the Milky Way bulge from VVV and 2MASS

Deriving metallicities from calcium triplet spectroscopy in combination with near-infrared photometry

Properties of RR Lyrae stars in the inner regions of the Large Magellanic Cloud

Contact Info

Product

Resources

About