Abundances of Metal-rich H II Regions in M51

By F. Bresolin, D. Garnett, Robert C. Kennicutt Jr.. 2004

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We have obtained multiobject spectroscopy of H II regions in the spiral galaxy M51 with the Keck I telescope and the Low Resolution Imaging Spectrometer. For 10 objects we have detected the auroral line [N II] λ5755, while [S III] λ6312 has been measured in seven of these. This has allowed us to measure the electron temperature of the gas and to derive oxygen, sulfur, and nitrogen abundances for the 10 H II regions. Contrary to expectations from previous photoionization models of a few H II regions in M51 and from strong-line abundance indicators, the O/H abundance is below the solar value for most objects, with the most metal-rich H II regions, P203 and CCM 72, having log(O/H) = -3.16 [~1.4(O/H)☉] and log(O/H) = -3.29 [~1.0 (O/H)☉], respectively. The reduction of O/H by factors of up to 2 or 3 with respect to previous indirect determinations has important consequences for the calibration of empirical abundance indicators, such as R23, in the abundance and excitation range found in the central regions of spiral galaxies. The abundance gradients in these galaxies can therefore be considerably flatter than those determined by using such empirical calibrations. The H II regions with a measured electron temperature span the range (0.19-1.04) R0 in galactocentric radius and indicate a shallow abundance gradient for M51: -0.02 ± 0.01 dex kpc-1. The S/O abundance ratio is found to be similar to previous determinations of its value in other spiral galaxies, log(S/O) ≈ -1.6. Therefore, we find no evidence for a variation in massive-star initial mass function or nucleosynthesis at high oxygen abundance. An overabundance of nitrogen is measured, with log(N/O) ≃ -0.6. On the basis of our new abundances, we revise the effective yield for M51, now found to be almost 4 times lower than previous estimates, and we discuss this result in the context of chemical evolution in galactic disks. Features from Wolf-Rayet stars (the blue bump at 4660 Å and the C III line at 5696 Å) are detected in a large number of H II regions in M51, with the C III λ5696 line found preferentially in the central, most metal-rich objects.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/befc474b298f01c5d4108dd7b86068819b9b105d

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GALAXY PAIRS IN THE SLOAN DIGITAL SKY SURVEY. I. STAR FORMATION, ACTIVE GALACTIC NUCLEUS FRACTION, AND THE LUMINOSITY/MASS–METALLICITY RELATION (2008, unknown): “It is well known that at high metallicities these strong line diagnostics show a positive offset relative to the metallicities determined from electron temperature methods (e.g., Bresolin et al. 2004; Bresolin 2007).”
THE MASS–METALLICITY RELATION WITH THE DIRECT METHOD ON STACKED SPECTRA OF SDSS GALAXIES (2012, background): “Because the strength of the auroral lines, especially [O iii] λ4363, is a 4 The original data can be found in Bresolin et al. (2004, 2005, 2009a, 2009b), Bresolin (2007), Campbell et al. (1986), Castellanos et al. (2002), de Blok & van der Hulst (1998), Esteban et al. (2009), Fierro et al. (1986),…”
On Extending the Mass-Metallicity Relation of Galaxies by 2.5 Decades in Stellar Mass (2006, methodology): “Recent work with nearby spiral galaxies has shown that bright-line oxygen abundances overestimate the true oxygen abundances by roughly 0.2–0.3 dex at metallicities solar and above (e.g., Stasińska 2002; Kennicutt et al. 2003a; Bresolin et al. 2004).”
Oxygen Abundance Determination in H II Regions: The Strong Line Intensities-Abundance Calibration Revisited (2005, methodology): “Our abundance scale is close to that of Bresolin et al. (2004): the average difference between the original and rederived oxygen abundances for the H ii regions of M51 is 0.03 dex.”
THE SPATIALLY RESOLVED STAR FORMATION LAW FROM INTEGRAL FIELD SPECTROSCOPY: VIRUS-P OBSERVATIONS OF NGC 5194 (2009, methodology): “Bresolin et al. (2004) measured the oxygen and sulfur abundance gradient in NGC 5194 using multi-object spectroscopy of 10 H II regions spanning a large range in radii.”
THE PdBI ARCSECOND WHIRLPOOL SURVEY (PAWS): ENVIRONMENTAL DEPENDENCE OF GIANT MOLECULAR CLOUD PROPERTIES IN M51 (2014, background): “Bresolin et al. (2004), and Moustakas et al. (2010) both found a metallicity close to solar with only a shallow radial gradient of −(0.02 ± 0.01) dex kpc−1, so we do not expect metallicity-dependent variations in the conversion factor across the PAWS FoV (see, e.g., Leroy et al. 2011, 2012).”
Probing the dust properties of galaxies up to submillimetre wavelengths. II. Dust-to-gas mass ratio trends with metallicity and the submm excess in dwarf galaxies (2011, background): “…would, in fact, make the galaxy move rightward, close to the James et al. (2002) relationship but we prefer to keep the value 8.7 estimated by Bresolin et al. (2004), which is based on high-quality Hii region observations and calculated in the arms of the galaxy, where star-forming regions…”
THE PdBI ARCSECOND WHIRLPOOL SURVEY (PAWS). I. A CLOUD-SCALE/MULTI-WAVELENGTH VIEW OF THE INTERSTELLAR MEDIUM IN A GRAND-DESIGN SPIRAL GALAXY (2013, methodology): “…conversion factor of XCO = min[4,675× I−0.32CO ]× 10 20 Z′ −.65 derived by Narayanan et al. (2012) we expect a range of (1− 3)× 1020 cm−2 (K km s−1)−1 for our measured ICO per pixel and assuming solar metallicity as observed for the PAWS FoV (Bresolin et al. 2004; Moustakas et al. 2010), i.e.”
Velocity-metallicity correlation for high-z DLA galaxies: evidence of a mass-metallicity relation? (2006, background): “In addition, the magnitude of such gradients in the discs of nearby spirals has been questioned recently (Bresolin et al. 2004).”
A VLT study of metal-rich extragalactic H II regions - I. Observations and empirical abundances (2005, methodology): “Recently Bresolin et al. (2004), in their study of metalrich H regions in the galaxy M 51, showed that the predicted T [S ] –”
Metallicity Calibrations and the Mass-Metallicity Relation for Star-forming Galaxies (2008, methodology): “Comparisons among the metallicities estimated using these methods reveal large discrepancies (e.g., Pilyugin 2001; Bresolin et al. 2004; Garnett et al. 2004b).”
THE YELLOW SUPERGIANT PROGENITOR OF THE TYPE II SUPERNOVA 2011dh IN M51 (2011, methodology): “Using the metallicity gradient derived by Bresolin et al. (2004) for H ii regions in M51, we adopt a metallicity at the SN position of ∼ 0.9 ± 0.1Z .”
Optical Star Formation Rate Indicators (2005, unknown): “…that the theoretical calibration of R23 is discrepant by 0.2–0.5 dex relative to electron-temperature abundance measurements, and may require revision to lower abundances (J. Moustakas et al. 2006b, in preparation; Pilyugin 2001; Kennicutt et al. 2003; Garnett et al. 2004; Bresolin et al. 2004).”