Effective temperature of ionizing stars of extragalactic HII regions

Abstract

The effective temperature (Teff) of the radiation field of the ionizing star(s) of a large sample of extragalactic HII regions was estimated using the R= log([OII](3727)/[OIII]5007) index. We used a grid of photoionization models to calibrate the Teff-R relation finding that it has a strong dependence with the ionizing parameter while it shows a weak direct dependence with the metallicity (variations in Z imply variations in U) of both the stellar atmosphere of the ionizing star and the gas phase of the HII region. Since the R index varies slightly with the Teff for values larger than 40 kK, the R index can be used to derive the Teff in 30-40 kK range. A large fraction of the ionization parameter variation is due to differences in the temperature of the ionizing stars and then the use of the (relatively) low Teff dependent S2=[S II](6717+31)/Ha emission-line ratio to derive the ionization parameter is preferable over others in the literature. We propose linear metallicity dependent relationships between S2 and U. Teff and metallicity estimations for a sample of 865 HII regions, whose emission-line intensities were compiled from the literature, do not show any Teff-Z correlation. On the other hand it seems to be hints of the presence of an anti-correlation between Teff-U. We found that the majority of the studied HII regions (87%) present Teff values in the range between 37 and 40 kK, with an average value of 38.5 kK. We also studied the variation of Teff as a function of the galactocentric distance for 14 spiral galaxies. Our results are in agreement with the idea of the existence of positive Teff gradients along the disk of spiral galaxies.

arXiv commentAccepted for publication in MNRAS. 13 pages. 8 figures

References in corpus (60)

• Starburst99: Synthesis Models for Galaxies with Active Star Formation
• Theoretical Modeling of Starburst Galaxies
• Metallicity Calibrations and the Mass-Metallicity Relation for Star-Forming Galaxies
• Using Strong Lines to Estimate Abundances in Extragalactic HII Regions and Starburst Galaxies
• The 'Forbidden' Abundance of Oxygen in the Sun
• The Galactic O-Star Spectroscopic Survey (GOSSS). II. Bright Southern Stars
• Spectroscopy of Outlying H II Regions in Spiral Galaxies: Abundances and Radial Gradients
• The 2013 Release of Cloudy
• The Composition Gradient in M101 Revisited. II. Electron Temperatures and Implications for the Nebular Abundance Scale
• The Galactic O-Star Spectroscopic Survey. I. Classification System and Bright Northern Stars in the Blue-Violet at R~2500
• New calibrations for abundance determinations in HII regions
• Extragalactic chemical abundances: do HII regions and young stars tell the same story? The case of the spiral galaxy NGC 300
• On the oxygen abundance determination in HII regions: High - metallicity regions
• Abundances of metal-rich H II regions in M51
• Deriving model-based T${}_e$-consistent chemical abundances in ionised gaseous nebulae
• The Physical Properties and Effective Temperature Scale of O-type Stars as a Function of Metallicity. II. Analysis of 20 More Magellanic Cloud Stars, and Results from the Complete Sample
• The flat oxygen abundance gradient in the extended disk of M83
• Integral field spectroscopy of a sample of nearby galaxies: II. Properties of the H ii regions
• Gas Metallicities in the Extended Disks of NGC 1512 and NGC 3621. Chemical Signatures of Metal Mixing or Enriched Gas Accretion?
• The localized chemical pollution in NGC 5253 revisited: Results from deep echelle spectrophotometry
• A VLT study of metal-rich extragalactic H II regions. I. Observations and empirical abundances
• The ionizing stars of extragalactic H II regions
• The Star Formation Rate Function for Redshift z~4-7 Galaxies: Evidence for a Uniform Build-Up of Star-Forming Galaxies During the First 3 Gyr of Cosmic Time
• Chemical abundances in M31 from HII regions
• Precision abundance analysis of bright HII galaxies
• "Counterpart" method for abundance determinations in HII regions
• Structure and Feedback in 30 Doradus II. Structure and Chemical Abundances
• The VLT-FLAMES Tarantula Survey XIV. The O-Type Stellar Content of 30 Doradus
• The temperature and ionization structure of the emitting gas in HII galaxies: Implications for the accuracy of abundance determinations
• The Physical Properties and Effective Temperature Scale of O-type Stars as a Function of Metallicity. III. More Results from the Magellanic Clouds
• New Radial Abundance Gradients for NGC 628 and NGC 2403
• An Empirical Test and Calibration of H II Region Diagnostics
• The VLT-FLAMES Tarantula Survey XVIII. Classifications and radial velocities of the B-type stars
• Chemical Abundances of H II Regions in the Starburst Galaxy NGC 1705
• The metal abundance of circumnuclear star forming regions in early type spirals. Spectrophotometric observations
• Analyzing derived metallicities and ionization parameters from model-based determinations in ionized gaseous nebulae
• The Runaways and Isolated O-Type Star Spectroscopic Survey of the SMC (RIOTS4)
• Calibration of Nebular Emission-Line Diagnostics: I. Stellar Effective Temperatures
• Photoionization models of the CALIFA HII regions. I. Hybrid models
• Massive star formation in Wolf-Rayet galaxies: II. Optical spectroscopy results
• Discovery of An Extremely Metal--Poor Galaxy: Optical Spectroscopy of UGCA 292
• The ionising cluster of 30 Doradus.IV. Stellar kinematics
• The ionized gas at the center of IC 10: A possible localized chemical pollution by Wolf-Rayet stars
• Kinematics of gas and stars in the circumnuclear starforming ring of NGC 3351
• Ages and metallicities of circumnuclear star formation regions from Gemini IFU observations
• GIANO Y-band spectroscopy of dwarf stars: Phosphorus, Sulphur, and Strontium abundances
• Structure and Feedback in 30 Doradus I: Observations
• Embedded Clusters in Giant Extragalactic HII Regions III. Extinction and Star Formation
• Interaction effects on galaxy pairs with Gemini/GMOS- II: Oxygen abundance gradients
• Interaction effects on galaxy pairs with Gemini/GMOS- I: Electron density
• O stars effective temperature and HII regions ionization parameter gradients in the Galaxy
• High resolution spectroscopy of the BCD galaxy Haro 15: II. Chemodynamics
• Integral field spectroscopy of HII regions in M33
• The Gini Coefficient as a Tool for Image Family Idenitification in Strong Lensing Systems with Multiple Images
• Abundance determination of multiple star-forming regions in the HII galaxy SDSS J165712.75+321141.4
• The circumnuclear environment of the peculiar galaxy NGC 3310
• On the derivation of dynamical masses of the stellar clusters in the circumnuclear region of NGC2903
• On the hardening of the ionizing radiation in HII regions across galactic discs through softness parameters
• Single-Star HII Regions as a Probe of Massive Star Spectral Energy Distributions
• Implications of the kinematical structure of circumnuclear star-forming regions on their derived properties

Cited by in corpus (12)

• Extreme Emission-Line Galaxies in SDSS. I. Empirical and model-based calibrations of chemical abundances
• MUSE spectroscopy of the ULX NGC 1313 X-1: a shock-ionised bubble, an X-ray photoionised nebula, and two supernova remnants
• Nature and chemical abundances of a sample of Lyman-$\alpha$ emitter objects at high redshift
• Alone on a wide wide sea. The origin of SECCO 1, an isolated star-forming gas cloud in the Virgo cluster
• Gas phase metallicity determinations in nearby AGNs with SDSS-IV MaNGA: evidence of metal poor accretion
• Effective temperature of ionizing stars of extragalactic HII regions -- II: nebular parameter relations based on CALIFA data
• Metal-THINGS: On the metallicity and ionization of ULX sources in NGC 925
• Revisiting the hardening of the stellar ionizing radiation in galaxy disks
• Chemical abundance of LINER galaxies -- Metallicity calibrations based on SDSS-IV MaNGA
• Metal-THINGS: The association and optical characterization of SNRs with HI holes in NGC 6946
• Chemical Abundance of the LINER galaxy UGC 4805 with SDSS-IV MaNGA
• Inner and outer star forming regions over the disks of spiral galaxies. II. A comparative of physical properties and evolutionary stages