Issue |
A&A
Volume 474, Number 3, November II 2007
|
|
---|---|---|
Page(s) | 807 - 814 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361:20077884 | |
Published online | 23 October 2007 |
Checking the reliability of equivalent width R23 for estimating the metallicities of galaxies
1
National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing 100012, PR China e-mail: ycliang@bao.ac.cn
2
GEPI, Observatoire de Paris-Meudon, 92195 Meudon, France
3
Department of Physics, Hebei Normal University, Shijiazhuang 050016, PR China
4
Department of Physics, Harbin University, Haerbin 150086, PR China
Received:
15
May
2007
Accepted:
8
August
2007
Aims.We verify whether the O/H abundances of galaxies can be derived from the equivalent width (EW) R23 instead of the extinction-corrected flux R23, and eventually propose a method of improving the reliability of this empirical method, which is often used for the non-flux calibrated spectra of galaxies.
Methods.We select 37 173 star-forming galaxies from the Second Data Release of the Sloan Digital Sky Survey (SDSS-DR2), which offers a wide range of properties to test the EW method.
Results.The EW-R23 method brings with it a significant bias: for the bulk of SDSS galaxies, it may affect the determination of (O/H) by factors ranging from –0.2 to 0.1 dex and for some galaxies by factors ranging from –0.5 to 0.2 dex. We characterize this discrepancy (or bias) by
)/(
,
which is virtually independent of dust extinction, while tightly correlating with Dn(4000), although at a lower significance, with (
) colors.
Conclusions.The EW-R23 method cannot be used as a proxy for the extinction-corrected flux R23 method. From analytical third-order polynomial fits of α versus () colors, we have been able to correct the EW-R23 method. With this additional and easy correction, the EW-R23 method provides O/H abundance values similar to those derived from the extinction-corrected flux R23 method with an accuracy of ±0.1 dex for >92% of the SDSS galaxies.
Key words: galaxies: abundances / galaxies: evolution / galaxies: ISM / galaxies: photometry / galaxies: spiral / galaxies: starburst
© ESO, 2007
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.