DEEP 2MASS PHOTOMETRY OF M67 AND CALIBRATION OF THE MAIN-SEQUENCEJ–KSCOLOR DIFFERENCE AS AN AGE INDICATOR

Sarajedini, Ata; Dotter, Aaron; Kirkpatrick, Allison

doi:10.1088/0004-637x/698/2/1872

Cited by 91 publications

(97 citation statements)

References 19 publications

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“…The results are quite similar overall, from the shape of the MDFs to the presence of metallicity gradients and distinct stellar populations (see next section), but the average metallicities found for each galaxy are systematically higher by ∼0.3 dex on average. However, a detailed comparison between different theoretical models goes beyond the goals of our work (for some examples, see Gallart et al 2005;Glatt et al 2008a,b;Goudfrooij et al 2009;Sarajedini et al 2009). …”

Section: Stellar Evolutionary Modelsmentioning

confidence: 99%

“…Distances and reddening values are taken from Karachentsev et al (2007) and from the Schlegel extinction maps (Schlegel et al 1998), respectively. The Dartmouth set of evolutionary models is able to reproduce particularly well the populations of old and intermediate-age clusters, while other models generally fail to simultaneously reproduce all features of the CMD for the correct, spectroscopically measured metallicity (e.g., Glatt et al 2008a,b;Sarajedini et al 2009). We choose a fixed age of 10 Gyr, and metallicities ranging from [Fe/H] = −2.5 to −0.3 in solar units.…”

Section: Metallicity Distribution Functionsmentioning

confidence: 99%

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A close look at the Centaurus A group of galaxies

Crnojević¹,

Grebel²,

Koch³

2010

A&A

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Aims. We study dwarf galaxies in the Centaurus A group to investigate their metallicity and possible environmental effects. The Centaurus A group (at ∼4 Mpc from the Milky Way) contains about 50 known dwarf companions of different morphologies and stellar contents, thus making it a very interesting target to study how these galaxies evolve. Methods. Here we present results for the early-type dwarf galaxy population in this group. We used archival HST/ACS data to study the resolved stellar content of 6 galaxies, together with isochrones from the Dartmouth stellar evolutionary models. Results. We derive photometric metallicity distribution functions of stars on the upper red giant branch via isochrone interpolation. The 6 galaxies are moderately metal-poor ( [Fe/H] = −1.56 to −1.08), and metallicity spreads are observed (internal dispersions of σ[Fe/H] = 0.10−0.41 dex). We also investigate whether intermediate-age stars are present, and discuss how these affect our results. The dwarfs exhibit flat to weak radial metallicity gradients. For the two most luminous, most metal-rich galaxies, we find statistically significant evidence of at least two stellar subpopulations: the more metal-rich stars are found in the center of the galaxies, while the metal-poor ones are more broadly distributed within the galaxies. Conclusions. We find no clear trend in the derived physical properties as a function of (present-day) galaxy position in the group, which may come from the small sample we investigate. We compare our results to the early-type dwarf population of the Local Group, and find no outstanding differences, even though the Centaurus A group is a denser environment that is possibly in a more advanced dynamical stage.

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Section: Stellar Evolutionary Modelsmentioning

confidence: 99%

Section: Metallicity Distribution Functionsmentioning

confidence: 99%

A close look at the Centaurus A group of galaxies

Crnojević¹,

Grebel²,

Koch³

2010

A&A

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“…Hence, for our final comparisons of isochrones with cluster observations, we decided to focus on the lower-MS extension of M 67, given that ugriz and BV I C JK S photometry is available for low-mass stars belonging to this system. [The 2MASS observations (Skrutskie et al 2006) were kindly provided to us by A. Dotter (see Sarajedini et al 2009), while the Johnson-Cousins photometry is from the same CADC website mentioned previously (see footnote 14). ]…”

Section: (Ngc 2682)mentioning

confidence: 99%

Synthetic stellar photometry – I. General considerations and new transformations for broad-band systems

Casagrande¹,

VandenBerg²

2014

Monthly Notices of the Royal Astronomical Society

257

321

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After a pedagogical introduction to the main concepts of synthetic photometry, colours and bolometric corrections in the Johnson-Cousins, 2MASS, and HST-ACS/WFC3 photometric systems are generated from MARCS synthetic fluxes for various [Fe/H] and [α/Fe] combinations, and virtually any value of E(B − V) 0.7. The successes and failures of model fluxes in reproducing the observed magnitudes are highlighted. Overall, extant synthetic fluxes predict quite realistic broad-band colours and bolometric corrections, especially at optical and longer wavelengths: further improvements of the predictions for the blue and ultraviolet spectral regions await the use of hydrodynamic models where the microturbulent velocity is not treated as a free parameter. We show how the morphology of the colour-magnitude diagram (CMD) changes for different values of [Fe/H] and [α/Fe]; in particular,how suitable colour combinations can easily discriminate between red giant branch and lower main sequence populations with different [α/Fe], due to the concomitant loops and swings in the CMD. We also provide computer programs to produce tables of synthetic bolometric corrections as well as routines to interpolate in them. These colour-T eff -metallicity relations may be used to convert isochrones for different chemical compositions to various bandpasses assuming observed reddening values, thus bypassing the standard assumption of a constant colour excess for stars of different spectral type. We also show how such an assumption can lead to significant systematic errors. The MARCS transformations presented in this study promise to provide important constraints on our understanding of the multiple stellar populations found in globular clusters (e.g., the colours of lower main sequence stars are predicted to depend strongly on [α/Fe]) and of those located towards/in the Galactic bulge.

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“…M67 is an ideal object for the purpose of model calibration, because it is a simple stellar system, with age and metallicity determinations from fitting stellar models to the colour-magnitude diagram (CMD). A current measure of M67 age is 3.5 -4 Gyr (see Sarajedini, Dotter & Kirkpatrick (2009)). M67 is also a desirable object for these models because it is approximately solar in metallicity and has got solar scaled element abundance ratios, which matches with the models (see discussion in M11, and their Figure 21).…”

Section: The Age-metallicity-stellar Library Degeneracymentioning

confidence: 99%

firefly (Fitting IteRativEly For Likelihood analYsis): a full spectral fitting code

Wilkinson

Maraston

Goddard

et al. 2017

Monthly Notices of the Royal Astronomical Society

172

177

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We present a new spectral fitting code, FIREFLY, for deriving the stellar population properties of stellar systems. FIREFLY is a chi-squared minimisation fitting code that fits combinations of single-burst stellar population models to spectroscopic data, following an iterative bestfitting process controlled by the Bayesian Information Criterion. No priors are applied, rather all solutions within a statistical cut are retained with their weight. Moreover, no additive or multiplicative polynomia are employed to adjust the spectral shape. This fitting freedom is envisaged in order to map out the effect of intrinsic spectral energy distribution (SED) degeneracies, such as age, metallicity, dust reddening on galaxy properties, and to quantify the effect of varying input model components on such properties. Dust attenuation is included using a new procedure, which was tested on Integral Field Spectroscopic (IFS) data in a previous paper. The fitting method is extensively tested with a comprehensive suite of mock galaxies, real galaxies from the Sloan Digital Sky Survey and Milky Way globular clusters. We also assess the robustness of the derived properties as a function of signal-to-noise ratio and adopted wavelength range. We show that FIREFLY is able to recover age, metallicity, stellar mass and even the star formation history remarkably well down to a S/N ∼ 5, for moderately dusty systems. Code and results are publicly available at WWW.ICG.PORT.AC.UK/FIREFLY.

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DEEP 2MASS PHOTOMETRY OF M67 AND CALIBRATION OF THE MAIN-SEQUENCEJ–K_SCOLOR DIFFERENCE AS AN AGE INDICATOR

Cited by 91 publications

References 19 publications

A close look at the Centaurus A group of galaxies

A close look at the Centaurus A group of galaxies

Synthetic stellar photometry – I. General considerations and new transformations for broad-band systems

firefly (Fitting IteRativEly For Likelihood analYsis): a full spectral fitting code

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