EFFECTS OF α-ELEMENT ENHANCEMENT AND THE THERMALLY PULSING-ASYMPTOTIC GIANT BRANCH ON SURFACE BRIGHTNESS FLUCTUATION MAGNITUDES AND BROADBAND COLORS

We investigate the effects of α-element enhancement and the thermally pulsing-asymptotic giant branch (TP-AGB) stars on the surface brightness fluctuation (SBF) magnitudes and broadband colors of simple stellar populations and compare to the empirical calibrations. We consider a broad range of ages and metallicities using the recently updated Teramo BaSTI isochrones. We find that the α-element-enhanced I-band SBF magnitudes are about 0.35 mag brighter and their integrated V − I colors are about 0.02 mag redder, mostly because of oxygen-enhancement effects on the upper red giant branch and AGB. We also demonstrate, using both the Teramo BaSTI and Padova isochrones, the acute sensitivity of SBF magnitudes to the presence of TP-AGB stars, particularly in the near-IR, but in the I band as well. Empirical SBF trends therefore hold great promise for constraining this important but still highly uncertain stage of stellar evolution. In a similar vein, non-negligible disparities are found among several different models available in the literature due to intrinsic model uncertainties.

[1]  L. Loinard,et al.  Tracers of stellar mass-loss. I. Optical and near-IR colours and surface brightness fluctuations , 2009, 0908.4133.

[2]  G. Raimondo.  JOINT ANALYSIS OF NEAR-INFRARED PROPERTIES AND SURFACE BRIGHTNESS FLUCTUATIONS OF LARGE MAGELLANIC CLOUD STAR CLUSTERS , 2009, 0907.1408.

[3]  Eric W. Peng,et al.  THE ACS FORNAX CLUSTER SURVEY. V. MEASUREMENT AND RECALIBRATION OF SURFACE BRIGHTNESS FLUCTUATIONS AND A PRECISE VALUE OF THE FORNAX–VIRGO RELATIVE DISTANCE , 2009, 0901.1138.

[4]  A. Dotter,et al.  STELLAR POPULATION MODELS AND INDIVIDUAL ELEMENT ABUNDANCES. II. STELLAR SPECTRA AND INTEGRATED LIGHT MODELS , 2008, 0812.1563.

[5]  On surface brightness fluctuations: probabilistic and statistical bases - I. Stellar population and theoretical surface brightness fluctuations , 2008, 0809.4491.

[6]  C. Maraston,et al.  NEAR-INFRARED PHOTOMETRY OF FOUR STELLAR CLUSTERS IN THE SMALL MAGELLANIC CLOUD , 2008, 0809.0495.

[7]  Santi Cassisi,et al.  A LARGE STELLAR EVOLUTION DATABASE FOR POPULATION SYNTHESIS STUDIES. IV. INTEGRATED PROPERTIES AND SPECTRA , 2008, 0809.0265.

[8]  Darko Jevremovic,et al.  The Dartmouth Stellar Evolution Database , 2008, 0804.4473.

[9]  Astronomy,et al.  Optical Surface Brightness Fluctuations of Shell Galaxies toward 100 Mpc , 2008, 0802.2509.

[10]  Belgium,et al.  Evolution of asymptotic giant branch stars. II. Optical to far-infrared isochrones with improved TP- , 2007, 0711.4922.

[11]  J. Ferguson,et al.  Spectral models for solar-scaled and α-enhanced stellar populations , 2007, Monthly Notices of the Royal Astronomical Society.

[12]  A. Dotter,et al.  Stellar Population Models and Individual Element Abundances. I. Sensitivity of Stellar Evolution Models , 2007, 0706.0808.

[13]  E. Baron,et al.  The ACS Survey of Galactic Globular Clusters. II. Stellar Evolution Tracks, Isochrones, Luminosity Functions, and Synthetic Horizontal-Branch Models , 2007, 0706.0847.

[14]  A. Pietrinferni,et al.  A Large Stellar Evolution Database for Population Synthesis Studies. III. Inclusion of the Full Asymptotic Giant Branch Phase and Web Tools for Stellar Population Analyses , 2006, astro-ph/0612669.

[15]  R. Schiavon.  Population Synthesis in the Blue. IV. Accurate Model Predictions for Lick Indices and UBV Colors in Single Stellar Populations , 2006, astro-ph/0611464.

[16]  R. Peletier,et al.  Stellar Populations as Building Blocks of Galaxies , 2007 .

[17]  S. F. Sanchez,et al.  IFU observations of the core of Abell 2218 , 2006, Proceedings of the International Astronomical Union.

[18]  L. Infante,et al.  An I-band calibration of surface brightness fluctuation measurements at blue colours , 2006 .

[19]  S. Faber,et al.  On the Age and Metallicity Estimation of Spiral Galaxies Using Optical and Near-Infrared Photometry , 2006, astro-ph/0605425.

[20]  Antonio Marin-Franch,et al.  Surface-brightness fluctuations in stellar populations. IAC-star models for the optical and near-IR , 2006 .

[21]  A. Cimatti,et al.  Evidence for TP-AGB Stars in High-Redshift Galaxies, and Their Effect on Deriving Stellar Population Parameters , 2006, astro-ph/0604530.

[22]  A. Pietrinferni,et al.  A Large Stellar Evolution Database for Population Synthesis Studies. II. Stellar Models and Isochrones for an α-enhanced Metal Distribution , 2006, astro-ph/0603721.

[23]  D. VandenBerg,et al.  The Victoria-Regina Stellar Models: Evolutionary Tracks and Isochrones for a Wide Range in Mass and Metallicity that Allow for Empirically Constrained Amounts of Convective Core Overshooting , 2005, astro-ph/0510784.

[24]  M. Mouhcine,et al.  New near-infrared surface brightness fluctuation models , 2005, astro-ph/0511823.

[25]  M. Cantiello,et al.  New Optical and Near-Infrared Surface Brightness Fluctuation Models. II. Young and Intermediate-Age Stellar Populations , 2005, astro-ph/0509020.

[26]  J. Tonry,et al.  The Advanced Camera for Surveys Virgo Cluster Survey. V. Surface Brightness Fluctuation Calibration for Giant and Dwarf Early-Type Galaxies , 2005 .

[27]  Hyun-chul Lee,et al.  α-Enhanced Integrated Lick/IDS Spectral Indices and Milky Way and M31 Globular Clusters and Early-Type Galaxies , 2005 .

[28]  David R. Alexander,et al.  Low-Temperature Opacities , 2005, astro-ph/0502045.

[29]  C. Maraston.  Evolutionary population synthesis: models, analysis of the ingredients and application to high‐z galaxies , 2004, astro-ph/0410207.

[30]  A. Pietrinferni,et al.  Color Transformations and Bolometric Corrections for Galactic Halo Stars: α-Enhanced versus Scaled-Solar Results , 2004, astro-ph/0408111.

[31]  C. Maraston,et al.  Probing the Red Giant Branch Phase Transition: Near-Infrared Photometry of Six Intermediate-Age Large Magellanic Cloud Clusters , 2004 .

[32]  S. Cassisi,et al.  A Large Stellar Evolution Database for Population Synthesis Studies. I. Scaled Solar Models and Isochrones , 2004, astro-ph/0405193.

[33]  C. Maraston,et al.  Probing the RGB-phase transition: Near-IR photometry of six intermediate age LMC clusters , 2004, astro-ph/0403410.

[34]  G. Bruzual,et al.  Stellar population synthesis at the resolution of 2003 , 2003, astro-ph/0309134.

[35]  G. Chabrier.  Galactic Stellar and Substellar Initial Mass Function , 2003, astro-ph/0304382.

[36]  Napoli,et al.  New Optical and Near-Infrared Surface Brightness Fluctuation Models: A Primary Distance Indicator Ranging from Globular Clusters to Distant Galaxies? , 2003, astro-ph/0303325.

[37]  S. Yi.  Uncertainties of Synthetic Integrated Colors as Age Indicators , 2002, astro-ph/0210202.

[38]  Rodger I. Thompson,et al.  Measuring Distances and Probing the Unresolved Stellar Populations of Galaxies Using Infrared Surface Brightness Fluctuations , 2002, astro-ph/0210129.

[39]  Garching,et al.  Stellar population models of Lick indices with variable element abundance ratios , 2002, astro-ph/0209250.

[40]  D. Alexander,et al.  The Y2 Isochrones for α-Element Enhanced Mixtures , 2002, astro-ph/0208175.

[41]  V. Narayanan,et al.  Early-type galaxy distances from the Fundamental Plane and surface brightness fluctuations , 2001, astro-ph/0111183.

[42]  Hyun-chul Lee.  Spectrophotometric Evolution of Old Stellar Systems , 2001, astro-ph/0107039.

[43]  P. Quinn,et al.  K-band versus I-band surface brightness fluctuations as distance indicators , 2001, astro-ph/0105025.

[44]  Gerard A. Luppino,et al.  The SBF Survey of Galaxy Distances. IV. SBF Magnitudes, Colors, and Distances , 2000, astro-ph/0011223.

[45]  P. Kroupa.  On the variation of the initial mass function , 2000, astro-ph/0009005.

[46]  J. Blakeslee,et al.  Stellar populations and surface brightness fluctuations: new observations and models , 2000, astro-ph/0008218.

[47]  N. Benı́tez,et al.  The Photometric Performance and Calibration of the Hubble Space Telescope Advanced Camera for Surveys , 2005, astro-ph/0507614.

[48]  Michael C. Liu,et al.  Theoretical Predictions for Surface Brightness Fluctuations and Implications for Stellar Populations of Elliptical Galaxies , 2000, astro-ph/0004367.

[49]  J. Tonry,et al.  The Surface Brightness Fluctuation Survey of Galaxy Distances. II. Local and Large-Scale Flows , 1999, astro-ph/9907062.

[50]  G. Worthey.  Abundance Ratio Trends and Nucleosynthesis in Elliptical Galaxies and Spheroids , 1998 .

[51]  H. Ford,et al.  Final Results from the Hubble Space Telescope Key Project to Measure the Hubble Constant , 1998, astro-ph/9801080.

[52]  J. Tonry,et al.  The SBF Survey of Galaxy Distances. I. Sample Selection, Photometric Calibration, and the Hubble Constant , 1996, astro-ph/9609113.

[53]  G. Worthey.  Comprehensive stellar population models and the disentanglement of age and metallicity effects , 1994 .

[54]  Oscar Straniero,et al.  The alpha -enhanced Isochrones and Their Impact on the FITS to the Galactic Globular Cluster System , 1993 .

[55]  G. Worthey.  The dependence of the brightness fluctuation distance indicator on stellar population age and metallicity , 1993 .

[56]  Sandra M. Faber,et al.  MG and Fe absorption features in elliptical galaxies , 1992 .

[57]  J. Tonry.  Surface Brightness Fluctuations: A Bridge from M31 to the Hubble Constant , 1991 .

[58]  J. Scalo.  The stellar initial mass function , 1986 .

[59]  I. Iben,et al.  Asymptotic Giant Branch Evolution and Beyond , 1983 .

[60]  E. Salpeter.  The Luminosity function and stellar evolution , 1955 .