Chemical abundances of the H II regions NGC 5461 and NGC 5471 in M 101, Derived from echelle spectrophotometry

Abstract

We present high resolution spectroscopic data of the two giant extragalactic H ii regions NGC 5461 and NGC 5471 in M 101. We calculate the physical conditions in the two nebulae with a large number of diagnostics, and determine their chemical abundances by applying ionization correction factors (icfs) to the observed ionic abundances. The comparison of the icfs based on photo-ionization models (Luridiana & Peimbert 2001; Luridiana et al. 1999) to those computed following the prescriptions by Mathis & Rosa (1991) shows large discrepancies for several elements, including nitrogen, neon and chlorine.

The nature of the Wolf-Rayet galaxy Mrk 209 from photoionization models

“…In order to calculate averages of the electron temperature, ionic fractions and ionization correction factors, we have considered volumetric integrations which fit better the observed values for models with a spherical geometry (Luridiana et al 2002) …”

On the electron temperatures in high-metallicity H ii regions

“…We believe that our criteria allow us to pick out the spectra of H ii regions with reliable measurements of at least one auroral line ([N ii ]λ5755, [O ii ]λ7325 and [O iii ]λ4363). Our final list consists of 76 spectra of H ii regions taken from Guseva, Izotov & Thuan (2000), Luridiana et al (2002), Vermeij et al (2002), Kennicutt, Bresolin & Garnett (2003), Lee et al (2003), Tsamis et al (2003), Peimbert (2003), Vílchez & Iglesias‐Páramo (2003), Bresolin, Garnett & Kennicutt (2004), Izotov & Thuan (2004), Garnett, Kennicutt & Bresolin (2004), Lee & Skillman (2004), Lee, Salzer & Melbourne (2004), Bresolin et al (2005), Thuan & Izotov (2005), Crockett et al (2006) and Bresolin (2007). The measured [O ii ]λ3727 +λ3729, [O iii ]λ4363, [O iii ]λ4959 +λ5007, [N ii ]λ5755, [N ii ]λ6548 +λ6584, [S ii ]λ6717 +λ6731 and [O ii ]λ7320 +λ7330 line intensities are listed in Table A1, which is available online.…”

On the electron temperature determination in high-metallicity H II regions

“…Recent measurements of the oxygen and nitrogen line intensities in high‐metallicity (12 + log (O/H) > 8.25) H ii regions were taken from Castellanos, Díaz & Terlevich (2002), Luridiana et al (2002), Peimbert (2003), Kennicutt, Bresolin & Garnett (2003), Tsamis et al (2003), Bresolin, Garnett & Kennicutt (2004) and Bresolin et al (2005). These spectroscopic data (40 data points) form the basis of the present study.…”