Astronomy and Astrophysics – Astronomy
Scientific paper
May 1992
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992aas...180.1606g&link_type=abstract
American Astronomical Society, 180th AAS Meeting, #16.06; Bulletin of the American Astronomical Society, Vol. 24, p.752
Astronomy and Astrophysics
Astronomy
Scientific paper
The recent discovery of a very high redshift, radio quiet Lya galaxy by Macchetto et al. (1992), detected at z=3.428, may provide new insight on primeval galaxies. This galaxy has been found while searching for cluster neighbours of the damped absorber of the QSO 0000-2619 placed at zabs=3.389 and of the metal rich absorption line system at zabs=3.409 detected in the spectrum of the same QSO by Turnshek et al. (1992). The newly discovered galaxy is characterized by a very faint UV continuum and by a strong Lya emission. A lower limit for the rest equivalent width of the Lya emission line is about 160 Angstroms, while the FWHM is 1000 km s(-1) . A 3 sigma detection at the position of the CIV line is also present. The Lya emission line is compatible with the characteristics of a young galaxy, a few 10(7) y after the beginning of its first star forming phase, according to recent spectral synthesis models.Supernovae remants could also produce such an intense Lya emission if their filling factor is small, which is also expected to occur in the early phase of the galaxy star formation. The presence in the spectrum of the CIV line can be explained by the hard radiation emerging from hot SNR which can photoionize the ISM, producing these high ionization emission lines. A partial contribution can also come from photoionization from hot, massive stars. The continuum is flat over the entire observed wavelength range and the ratio \Lya/CIV is about 0.1, significantly lower than what usually found in Seyfert 1 galaxies.The star formation rate calculated, according to the model by Charlot & Fall, 1991, from the Lya luminosity assuming no dust obscuration, is about 20 hh M_&sun; y(-1) (q_0=0.5), a value which is well inside the range of possibilities one would expect from primeval galaxies and which is smaller than the SFR usually inferred from high redshift radio galaxies.
Giavalisco Mauro
Macchetto Ferdinando
Sparks William B.
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