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28 March 2024 |
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Gas Motion Statistics of Lya Emitters at z~2 Using UV and Optical Emission Lines | Takuya Hashimoto
; Masami Ouchi
; Kazuhiro Shimasaku
; Yoshiaki Ono
; Kimihiko Nakajima
; Michael Rauch
; Janice Lee
; Sadanori Okamura
; | Date: |
11 Jun 2012 | Abstract: | We present the results of Magellan/MMIRS and Keck/NIRSPEC spectroscopy for
five Lya emitters (LAEs) at z=2.2 for which high-resolution Lya spectra are
available. We detect Ha emission for all five objects and [OII], Hb, and/or
[OIII] emission for some, from which the systemic velocity is measured. We
obtain the offset of Lya line with respect to the systemic velocity,
Delta_v_Lya. For a sample of eight z~2-3 LAEs without AGN from our study and
the literature, we find the average offset velocity of Delta_v_Lya = 145
^{+45}_{-23} km s^{-1}, which is significantly smaller than that of Lyman Break
Galaxies (LBGs), Delta_v_Lya ~ 400 km s^{-1}. Since any of the LAEs with
positive Delta_v_Lya has an asymmetric Lya profile that cannot be explained by
static gas cloud models, this average Delta_v_Lya implies that most LAEs have a
gas outflow but with a systematically smaller velocity than those of LBGs.
Interestingly, we find an anti-correlation between Lya equivalent width (EW)
and Delta_v_Lya in the compilation of the LAE and LBG samples that galaxies
with stronger Lya emission have smaller Delta_v_Lya. Although its physical
origin is unknown, this anti-correlation result would challenge the hypothesis
that a strong outflow produces a large Lya EW because of reduced numbers of
resonant scattering through the inter-stellar medium. If LAEs at z>6 have
similarly small Delta_v_Lya, some reionization models need to revise the amount
of Lya photons scattered by the inter-galactic medium. | Source: | arXiv, 1206.2316 | Services: | Forum | Review | PDF | Favorites |
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