- ID:
- ivo://CDS.VizieR/J/ApJ/513/168
- Title:
- HST observations of carbon in spiral galaxies
- Short Name:
- J/ApJ/513/168
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present measurements of the gas-phase abundance ratio C/O in six H II regions in the spiral galaxies M101 and NGC 2403, based on ultraviolet spectroscopy using the Faint Object Spectrograph on the Hubble Space Telescope. The ratios of C to O increase systematically with O/H in both galaxies, from log(C/O){~=}-0.8 at log(O/H){~=}-4.0 to log(C/O){~=}-0.1 at log(O/H){~=}-3.4. C/N shows no correlation with O/H. The rate of increase of C/O is somewhat uncertain because of uncertainty as to the appropriate UV reddening law and uncertainty in the metallicity dependence on grain depletions. However, the trend of increasing C/O with O/H is clear, confirming and extending the trend in C/O indicated previously from observations of irregular galaxies. Our data indicate that the radial gradients in C/H across spiral galaxies are steeper than the gradients in O/H. Comparing the data to chemical-evolution models for spiral galaxies shows that models in which the massive star yields do not vary with metallicity predict radial C/O gradients that are much flatter than the observed gradients.
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- ID:
- ivo://CDS.VizieR/J/A+A/391/945
- Title:
- HST photometry of 74 galactic globular clusters
- Short Name:
- J/A+A/391/945
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the complete photometric database and the color-magnitude diagrams for 74 Galactic globular clusters observed with the HST/WFPC2 camera in the F439W and F555W bands. A detailed discussion of the various reduction steps is also presented, and of the procedures to transform instrumental magnitudes into both the HST F439W and F555W flight system and the standard Johnson B and V systems. We also describe the artificial star experiments which have been performed to derive the star count completeness in all the relevant branches of the color magnitude diagram. The entire photometric database and the completeness function will be made available on the Web immediately after the publication of the present paper.
- ID:
- ivo://CDS.VizieR/J/ApJ/521/577
- Title:
- HST studies of the WLM globular cluster
- Short Name:
- J/ApJ/521/577
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained V and I images of the lone globular cluster that belongs to the dwarf Local Group irregular galaxy known as WLM. The color-magnitude diagram of the cluster shows that it is a normal old globular cluster with a well-defined giant branch reaching to M_V_=-2.5, a horizontal branch at M_V_=+0.5, and a subgiant branch extending to our photometry limit of M_V_=+2.0. A best fit to theoretical isochrones indicates that this cluster has a metallicity of [Fe/H]=-1.52{+/-}0.08 and an age of 14.8{+/-}0.6 Gyr, thus indicating that it is similar to normal old halo globulars in our Galaxy. From the fit we also find that the distance modulus of the cluster is 24.73{+/-}0.07 and the extinction is A_V_=0.07{+/-}0.06, both values that agree within the errors with data obtained for the galaxy itself by others.
