NEW DETECTIONS OF LY ALPHA EMISSION IN YOUNG GALAXIES

被引:52
作者
TERLEVICH, E [1 ]
DIAZ, AI [1 ]
TERLEVICH, R [1 ]
VARGAS, MLG [1 ]
机构
[1] UNIV AUTONOMA MADRID,FAC CIENCIAS,DEPT FIS TEOR,E-28049 MADRID,SPAIN
关键词
H-II REGIONS; GALAXIES; -; ABUNDANCES; FORMATION; STARBURST; ULTRAVIOLET;
D O I
10.1093/mnras/260.1.3
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We report IUE observations of two extremely low-metallicity H II galaxies. Ly alpha emission was detected in both galaxies. Our results confirm previous findings that young br unevolved galaxies exhibit weak or absent Ly alpha emission combined with a strong UV continuum, and that the Ly alpha/H beta ratio and metal content are correlated in the sense that the lower the abundance, the larger the ratio. This supports the hypothesis that in the higher metallicity systems Ly a is destroyed by dust absorption. At redshifts of between 2 and 3, Ly alpha emission comparable to the strongest detected in H II galaxies [L(Ly alpha) approximately 5 x 10(42) erg s-1] would be barely visible; this fact can explain the relative lack of success in detecting Ly alpha emission associated with low-metallicity damped Ly alpha systems in QSOs. Our results cast doubt on claims of detection of high-redshift young galaxies associated with active galaxies, or with strong Ly alpha and both C IV and He II, since they may represent very extended narrow-line regions photoionized by radiation with a power-law spectrum rather than by normal hot stars.
引用
收藏
页码:3 / 8
页数:6
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