TY - JOUR
T1 - Spectroscopic properties of the z ≈ 4.5 Lyα emitters
AU - Dawson, Steve
AU - Rhoads, James E.
AU - Malhotra, Sangeeta
AU - Stern, Daniel
AU - Dey, Arjun
AU - Spinrad, Hyron
AU - Jannuzi, Buell T.
AU - Wang, Junxian
AU - Landes, Emily
PY - 2004/12/20
Y1 - 2004/12/20
N2 - We present Keck Low Resolution Imaging Spectrometer optical spectra of 17 Lyα-emitting galaxies and one Lyman break galaxy at z ≈ 4.5 discovered in the Large Area Lyman Alpha survey. The survey has identified a sample of ∼350 candidate Lyα-emitting galaxies at z ≈ 4.5 in a search volume of 1.5 × 106 comoving Mpc3. We targeted 25 candidates for spectroscopy; hence, the 18 confirmations presented herein suggest a selection reliability of 72%. The large equivalent widths (median Wλrest ≈ 80 Å) but narrow physical widths (Δv < 500 km s-1) of the Lyα emission lines, along with the lack of accompanying high-ionization state emission lines, suggest that these galaxies are young systems powered by star formation rather than by active galactic nucleus activity. Theoretical models of galaxy formation in the primordial universe suggest that a small fraction of Lyα-emitting galaxies at z ≈ 4.5 may still be nascent, metal-free objects. Indeed, we find with 90% confidence that three to five of the confirmed sources show W λrest > 240 Å, exceeding the maximum Lyα equivalent width predicted for normal stellar populations. Nonetheless, we find no evidence for He II λ1640 emission in either individual or composite spectra, indicating that although these galaxies are young, they are not truly primitive, Population III objects.
AB - We present Keck Low Resolution Imaging Spectrometer optical spectra of 17 Lyα-emitting galaxies and one Lyman break galaxy at z ≈ 4.5 discovered in the Large Area Lyman Alpha survey. The survey has identified a sample of ∼350 candidate Lyα-emitting galaxies at z ≈ 4.5 in a search volume of 1.5 × 106 comoving Mpc3. We targeted 25 candidates for spectroscopy; hence, the 18 confirmations presented herein suggest a selection reliability of 72%. The large equivalent widths (median Wλrest ≈ 80 Å) but narrow physical widths (Δv < 500 km s-1) of the Lyα emission lines, along with the lack of accompanying high-ionization state emission lines, suggest that these galaxies are young systems powered by star formation rather than by active galactic nucleus activity. Theoretical models of galaxy formation in the primordial universe suggest that a small fraction of Lyα-emitting galaxies at z ≈ 4.5 may still be nascent, metal-free objects. Indeed, we find with 90% confidence that three to five of the confirmed sources show W λrest > 240 Å, exceeding the maximum Lyα equivalent width predicted for normal stellar populations. Nonetheless, we find no evidence for He II λ1640 emission in either individual or composite spectra, indicating that although these galaxies are young, they are not truly primitive, Population III objects.
KW - Galaxies: evolution
KW - Galaxies: high-redshift
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U2 - 10.1086/425572
DO - 10.1086/425572
M3 - Article
AN - SCOPUS:13944271075
VL - 617
SP - 707
EP - 717
JO - Astrophysical Journal
JF - Astrophysical Journal
SN - 0004-637X
IS - 2 I
ER -