71 research outputs found
The Stellar Mass, Star Formation Rate and Dark Matter Halo Properties of LAEs at
We present average stellar population properties and dark matter halo masses
of \lya emitters (LAEs) from SED fitting and clustering analysis,
respectively, using objects () in four separate
fields of deg in total. With an average stellar mass of and star formation rate of , the LAEs lie on an extrapolation
of the star-formation main sequence (MS) to low stellar mass. Their effective
dark matter halo mass is estimated to be $4.0_{-2.9}^{+5.1} \times 10^{10}\
{\mathrm M_\odot}1.22^{+0.16}_{-0.18}z \sim 21.8\, \pm\, 0.396\%.
However, the difference in the bias values can be explained if cosmic variance
is taken into account. If such a low halo mass implies a low HI gas mass, this
result appears to be consistent with the observations of a high \lya escape
fraction. With the low halo masses and ongoing star formation, our LAEs have a
relatively high stellar-to-halo mass ratio (SHMR) and a high efficiency of
converting baryons into stars. The extended Press-Schechter formalism predicts
that at z=0z \sim 2$ as some previous
studies have reported for the LMC itself.Comment: 34 pages, 15 figures, 6 tables. Accepted for publication in PAS
A hard ionizing spectrum in z=3-4 Lyα emitters with intense [OIII] emission: Analogs of galaxies in the reionization era?
We present Keck/MOSFIRE spectra of the diagnostic nebular emission lines [O iii]λλ5007,4959, [O ii]λ3727, and Hβ for a sample of 15 redshift z≃3.1\mbox-3.7 Lyα emitters (LAEs) and Lyman break galaxies (LBGs). In conjunction with spectra from other surveys, we confirm earlier indications that LAEs have a much higher [O iii]/[O ii] line ratio than is seen in similar redshift LBGs. By comparing their distributions on a [O iii]/[O ii] versus R23 diagram, we demonstrate that this difference cannot arise solely because of their lower metallicities but most likely is due to a harder ionizing spectrum. Using measures of Hβ and recombination theory, we demonstrate, for a subset of our LAEs, that ξion—the number of Lyman continuum photons per UV luminosity—is indeed 0.2–0.5 dex larger than for typical LBGs at similar redshifts. Using photoionization models, we estimate the effect this would have on both [O iii]/[O ii] and R23 and conclude such a hard spectrum can only partially explain such intense line emission. The additional possibility is that such a large [O iii]/[O ii] ratio is in part due to density rather than ionization bound nebular regions, which would imply a high escape fraction of ionizing photons. We discuss how further observations could confirm this possibility. Clearly LAEs with intense [O iii] emission represent a promising analog of those z > 7 sources with similarly strong lines that are thought to be an important contributor to cosmic reionization
The dominant origin of diffuse Lyα halos around Lyα emitters explored by spectral energy distribution fitting and clustering analysis
The physical origin of diffuse Lyα halos (LAHs) around star-forming galaxies is still a matter of debate. We present the dependence of LAH luminosity [L(Lyα)_H] on the stellar mass (M⋆), star formation rate, color excess [E(B − V)⋆], and dark matter halo mass (M_h) of the parent galaxy for ∼900 Lyα emitters (LAEs) at z ∼ 2 divided into ten subsamples. We calculate L(Lyα)_H using the stacked observational relation between L(Lyα)H and central Lyα luminosity of Momose et al. (2016, MNRAS, 457, 2318), which we find agrees with the average trend of VLT/MUSE-detected individual LAEs. We find that our LAEs have relatively high L(Lyα)_H despite low M⋆ and M_h, and that L(Lyα)_H remains almost unchanged with M⋆ and perhaps with M_h. These results are incompatible with the cold stream (cooling radiation) scenario and the satellite-galaxy star-formation scenario, because the former predicts fainter L(Lyα)_H and both predict steeper L(Lyα)_H vs. M⋆ slopes. We argue that LAHs are mainly caused by Lyα photons escaping from the main body and then scattering in the circum-galactic medium. This argument is supported by LAH observations of Hα emitters (HAEs). When LAHs are taken into account, the Lyα escape fractions of our LAEs are about ten times higher than those of HAEs with similar M⋆ or E(B − V)⋆, which may partly arise from lower H I gas masses implied from lower M_h at fixed M⋆, or from another Lyα source in the central part
The dominant origin of diffuse Ly halos around LAEs explored by SED fitting and clustering analysis
The physical origin of diffuse Ly halos (LAHs) around star-forming
galaxies is still a matter of debate. We present the dependence of LAH
luminosity () on the stellar mass (), ,
color excess (), and dark matter halo mass () of the
parent galaxy for Ly emitters (LAEs) at divided
into ten subsamples. We calculate using the stacked
observational relation between and central Ly
luminosity by Momose et al. (2016), which we find agrees with the average trend
of VLT/MUSE-detected individual LAEs. We find that our LAEs have relatively
high despite low and , and that
remains almost unchanged with and perhaps with
. These results are incompatible with the cold stream (cooling
radiation) scenario and the satellite-galaxy star-formation scenario, because
the former predicts fainter and both predict steeper
vs. slopes. We argue that LAHs are mainly
caused by Ly photons escaping from the main body and then scattered in
the circum-galactic medium. This argument is supported by LAH observations of
H emitters (HAEs). When LAHs are taken into account, the Ly
escape fractions of our LAEs are about ten times higher than those of HAEs with
similar or , which may partly arise from lower HI gas
masses implied from lower at fixed , or from another
Ly source in the central part.Comment: Published in PASJ; 35 pages, 13 figures, 6 table
Median Surface Brightness Profiles of Lyman- Haloes in the MUSE Extremely Deep Field
We present the median surface brightness profiles of diffuse Ly
haloes (LAHs) around star-forming galaxies by stacking 155 spectroscopically
confirmed Ly emitters (LAEs) at 3<z<4 in the MUSE Extremely Deep Field
(MXDF), with median Ly luminosity . After correcting for a systematic surface brightness
offset we identified in the datacube, we detect extended Ly emission
out to a distance of 270 kpc. The median Ly surface brightness profile
shows a power-law decrease in the inner 20 kpc, and a possible flattening trend
at larger distance. This shape is similar for LAEs with different Ly
luminosities, but the normalisation of the surface brightness profile increases
with luminosity. At distances larger than 50 kpc, we observe strong overlap of
adjacent LAHs, and the Ly surface brightness is dominated by the LAHs
of nearby LAEs. We find no clear evidence of redshift evolution of the observed
Ly profiles when comparing with samples at 4<z<5 and 5<z<6. Our results
are consistent with a scenario in which the inner 20 kpc of the LAH is powered
by star formation in the central galaxy, while the LAH beyond a radius of 50
kpc is dominated by photons from surrounding galaxies.Comment: Submitted to A&
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