Document Type


Publication Date


Publication Title

Astrophysical Journal


We report the detection of a galaxy associated with the damped Lyα absorbing cloud seen at z = 2.309 toward the QSO PHL 957 (zem = 2.681). The galaxy was discovered in deep Fabry-Perot narrow-band CCD frames and was subsequently imaged spectroscopically. In addition to a strong but narrow Lyα emission line (FLyα = 5.6 × 10-16 ergs s-1 cm-2, FWHM ∼ 700 km s-1) and weaker C IV and He II lines, the object shows continuum at V ∼ 24, with a slope (in Fν) rising slightly toward the red, similar to what is seen in high-redshift radio galaxies; however, the galaxy does not correspond to any known radio source in the literature. The detected emission lines and continuum are most easily interpreted as light from hot, recently formed stars, implying not only a sizable star formation rate (SFR ≥ 5 M⊙ yr-1) but also a scarcity of dust, which readily quenches Lyα photons. The emission region appears to be marginally resolved spatially and is located 48 to the NW of the QSO, corresponding to a projected distance of 270h-1 kpc (for q0 = 0.1); the velocity difference with respect to the damped Lya cloud is ∼350 km s-1. The spatial correlation of the absorbing cloud and the companion galaxy supports the interpretation of damped Lyα clouds as objects fundamentally different from the lower column density Lyα forest clouds, which show weak or no clustering. The absorption trough itself shows no Lya emission, extended or unresolved, in either the Fabry-Perot frames or in deep, moderate resolution (∼3 Å FWHM), two-dimensional spectra, down to a limiting flux (3 σ) for an unresolved line of 2 ×10-17 ergs s-1 cm-2, ∼30 times fainter than the Lyα flux detected from the companion galaxy. The lack of strong Lya emission from the absorbing cloud can be interpreted as evidence either for a low SFR or for heavy dust obscuration.


Cosmology, Galaxies: formation, Quasars




2 PART 2





Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.


© The Authors


Archived as published.



To view the content in your browser, please download Adobe Reader or, alternately,
you may Download the file to your hard drive.

NOTE: The latest versions of Adobe Reader do not support viewing PDF files within Firefox on Mac OS and if you are using a modern (Intel) Mac, there is no official plugin for viewing PDF files within the browser window.