AN INITIAL MASS FUNCTION STUDY OF THE DWARF STARBURST GALAXY NGC 4214

The production rate of ionizing photons in young (≤8 Myr), unresolved stellar clusters in the nearby irregular galaxy NGC 4214 is probed using multi-wavelength Hubble Space Telescope WFC3 data. We normalize the ionizing photon rate by the cluster mass to investigate the upper end of the stellar initial mass function (IMF). We have found that within the uncertainties the upper end of the stellar IMF appears to be universal in this galaxy, and that deviations from a universal IMF can be attributed to stochastic sampling of stars in clusters with masses ≾ 10^3 M_☉. Furthermore, we have found that there does not seem to be a dependence of the maximum stellar mass on the cluster mass. We have also found that for massive clusters, feedback may cause an underrepresentation in Hα luminosities, which needs to be taken into account when conducting this type of analysis.

[1]  C. Lada,et al.  Embedded Clusters in Molecular Clouds , 2003, astro-ph/0301540.

[2]  H Germany,et al.  Diverging UV and Hα fluxes of star-forming galaxies predicted by the IGIMF theory , 2009, 0901.4335.

[3]  Mark Clampin,et al.  The Low End of the Initial Mass Function in Young Large Magellanic Cloud Clusters. I. The Case of R136 , 2000 .

[4]  R. Davies,et al.  Systematic variation of the stellar initial mass function in early-type galaxies , 2012, Nature.

[5]  V. Luridiana,et al.  Confidence limits of evolutionary synthesis models. IV. Moving forward to a probabilistic formulation , 2006 .

[6]  The University of Toledo,et al.  USING Hα MORPHOLOGY AND SURFACE BRIGHTNESS FLUCTUATIONS TO AGE-DATE STAR CLUSTERS IN M83 , 2011, 1103.4026.

[7]  Denis Foo Kune,et al.  Starburst99: Synthesis Models for Galaxies with Active Star Formation , 1999, astro-ph/9902334.

[8]  Baltimore,et al.  Hubble Space Telescope/WFPC2 and VLA Observations of the Ionized Gas in the Dwarf Starburst Galaxy NGC 4214 , 2000 .

[9]  Benjamin D. Johnson,et al.  MODELING THE EFFECTS OF STAR FORMATION HISTORIES ON Hα AND ULTRAVIOLET FLUXES IN NEARBY DWARF GALAXIES , 2011, 1109.2905.

[10]  P. Kroupa,et al.  Galactic-Field Initial Mass Functions of Massive Stars , 2003 .

[11]  M. Fumagalli,et al.  STOCHASTIC STAR FORMATION AND A (NEARLY) UNIFORM STELLAR INITIAL MASS FUNCTION , 2011, 1105.6101.

[12]  Benjamin D. Johnson,et al.  COMPARISON OF Hα AND UV STAR FORMATION RATES IN THE LOCAL VOLUME: SYSTEMATIC DISCREPANCIES FOR DWARF GALAXIES , 2009, 0909.5205.

[13]  B. Elmegreen.  On the Similarity between Cluster and Galactic Stellar Initial Mass Functions , 2006, astro-ph/0605520.

[14]  M. Oey.  ON THE ORIGIN OF THE SALPETER SLOPE FOR THE INITIAL MASS FUNCTION , 2011, 1108.2287.

[15]  D. Nidever,et al.  THE IMPORTANCE OF NEBULAR CONTINUUM AND LINE EMISSION IN OBSERVATIONS OF YOUNG MASSIVE STAR CLUSTERS , 2009, 0911.0447.

[16]  S. Sakai,et al.  An Hα Imaging Survey of Galaxies in the Local 11 Mpc Volume , 2004, 0807.2035.

[17]  P. Massey.  Massive Stars in the Local Group: Implications for Stellar Evolution and Star Formation , 2003 .

[18]  The Luminosity Function of Star Clusters in Spiral Galaxies , 2002, astro-ph/0206295.

[19]  O. I. Wong,et al.  EVIDENCE FOR A NONUNIFORM INITIAL MASS FUNCTION IN THE LOCAL UNIVERSE , 2009, 0902.0384.

[20]  Edward L. Fitzpatrick,et al.  Correcting for the Effects of Interstellar Extinction , 1998, astro-ph/9809387.

[21]  M. M. Hanson,et al.  MASSCLEANage—STELLAR CLUSTER AGES FROM INTEGRATED COLORS , 2010, 1007.3718.

[22]  E. Skillman,et al.  Elemental Abundance Variations and Chemical Enrichment from Massive Stars in Starbursts. II. NGC 1569 , 1996, astro-ph/9706235.

[23]  M. Fumagalli,et al.  SLUG—STOCHASTICALLY LIGHTING UP GALAXIES. I. METHODS AND VALIDATING TESTS , 2011, 1106.3072.

[24]  M. Dopita,et al.  THE LUMINOSITY, MASS, AND AGE DISTRIBUTIONS OF COMPACT STAR CLUSTERS IN M83 BASED ON HUBBLE SPACE TELESCOPE/WIDE FIELD CAMERA 3 OBSERVATIONS , 2010, 1007.5237.

[25]  D. Calzetti,et al.  NEW CONSTRAINTS ON MASS-DEPENDENT DISRUPTION OF STAR CLUSTERS IN M51 , 2011, 1101.2869.

[26]  C. Leitherer,et al.  Hubble Space Telescope Ultraviolet Imaging and Spectroscopy of the Bright Starburst in the Wolf-Rayet Galaxy NGC 4214 , 1996 .

[27]  P. Kroupa,et al.  The relation between the most-massive star and its parental star cluster mass , 2009, 0909.1555.

[28]  Benjamin D. Johnson,et al.  A GALEX ULTRAVIOLET IMAGING SURVEY OF GALAXIES IN THE LOCAL VOLUME , 2010, 1009.4705.

[29]  F. Walter,et al.  The Interaction between the Interstellar Medium and Star Formation in the Dwarf Starburst Galaxy NGC 4214 , 2000, astro-ph/0011098.

[30]  E. Pellegrini,et al.  THE OPTICAL DEPTH OF H ii REGIONS IN THE MAGELLANIC CLOUDS , 2012, 1202.3334.

[31]  A. Kinney,et al.  The Dust Content and Opacity of Actively Star-forming Galaxies , 1999, astro-ph/9911459.

[32]  J. Eldridge.  Stochasticity, a variable stellar upper mass limit, binaries and star formation rate indicators , 2011, 1106.4311.

[33]  M. Dopita,et al.  Supernova remnants, planetary nebulae and the distance to NGC 4214 , 2010 .

[34]  J. MacKenty,et al.  The Young Stellar Population of NGC 4214 as Observed with the Hubble Space Telescope. II. Results , 2007, 0708.3510.

[35]  J. M. Apell'aniz.  Accepted for publication in the Astrophysical Journal Biases on initial mass function determinations. II. Real multiple systems and chance superpositions 1 , 2022 .

[36]  Glenn E. Ciolek,et al.  From Darkness to Light: Origin and Evolution of Young Stellar Clusters , 2007 .

[37]  M. Cervino V. Luridiana.  Physical limits to the validity of synthesis models - The Lowest Luminosity Limit , 2003 .

[38]  J. Gallagher,et al.  On the formation of star clusters in the merger NGC 6240 , 2003, astro-ph/0306446.

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

[40]  B. Elmegreen,et al.  The cluster birthline in M33 , 2009, 0901.1530.

[41]  D. Weinberg,et al.  On the evolutionary history of stars and their fossil mass and light , 2006, astro-ph/0604534.

[42]  S. Bamford,et al.  Galaxy and Mass Assembly (GAMA): the star formation rate dependence of the stellar initial mass function , 2011, 1104.2379.

[43]  M. Cerviño,et al.  Modeling the ionizing spectra of H II regions: individual stars versus stellar ensembles , 2010, 1010.3031.

[44]  R. Walterbos,et al.  THE STELLAR MASS DISTRIBUTION IN THE GIANT STAR FORMING REGION NGC 346 , 2007, 0710.0558.

[45]  A. Hopkins,et al.  Extragalactic constraints on the initial mass function , 2008, 0809.2518.

[46]  J. Alves,et al.  No evidence of mass segregation in massive young clusters , 2008, 0811.3213.

[47]  A. Seth,et al.  THE ACS NEARBY GALAXY SURVEY TREASURY. VII. THE NGC 4214 STARBURST AND THE EFFECTS OF STAR FORMATION HISTORY ON DWARF MORPHOLOGY , 2011, 1104.0033.

[48]  J. Anderson,et al.  MIXED POPULATIONS IN GLOBULAR CLUSTERS: ET TU, 47 TUC? , 2009, 0904.1626.

[49]  Thierry Montmerle,et al.  From darkness to light : origin and evolution of young stellar clusters : proceedings of a meeting held in Cargèse, Corsica, France, 3-8 April 2000 , 2001 .

[50]  K. Glazebrook,et al.  Evidence for a Nonuniversal Stellar Initial Mass Function from the Integrated Properties of SDSS Galaxies , 2007, 0711.1309.

[51]  G. Gavazzi,et al.  HIGH-MASS STAR FORMATION IN NORMAL LATE-TYPE GALAXIES: OBSERVATIONAL CONSTRAINTS TO THE INITIAL MASS FUNCTION , 2009, 0910.3521.

[52]  C. Conroy,et al.  CONFIRMATION OF ENHANCED DWARF-SENSITIVE ABSORPTION FEATURES IN THE SPECTRA OF MASSIVE ELLIPTICAL GALAXIES: FURTHER EVIDENCE FOR A NON-UNIVERSAL INITIAL MASS FUNCTION , 2011, 1102.3431.

[53]  J. Lee,et al.  On how leakage can affect the star formation rate estimation using Hα luminosity , 2012, 1204.4502.

[54]  Cambridge,et al.  A Universal Stellar Initial Mass Function? A critical look at variations in extreme environments , 2010, 1001.2965.

[55]  J. C. Lee,et al.  A METHOD FOR MEASURING VARIATIONS IN THE STELLAR INITIAL MASS FUNCTION , 2010, 1007.3188.