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”Stellar Populations of Lyman Alpha Emitters at z~6-7: Constraints on
the Escape Fraction of Ionizing Photons from Galaxy Building Blocks”
『赤方偏移約 6-7 のライマン・アルファ輝線銀河の星の種族: 銀河の部品からの
電離光子離脱率への制限』
Abstract:
Lya emitters (LAEs) are a galaxy population commonly seen at high
redshift. Studying the stellar population of LAEs is essential to
understand their physical nature and to reveal the relationship
between LAEs and other high-redshift galaxies. At z ~ 6-7, a few
studies have reported on stellar populations of LAEs, but they are all
based on a very small sample and consensus has not been reached.
We investigate the stellar populations of LAEs at z=5.7 and 6.6 in a
0.65 deg^2 sky of the Subaru/XMM-Newton Deep Survey Field. We produce
stacked multiband images at each redshift from 165 (z=5.7) and 91
(z=6.6) objects, to derive typical spectral energy distributions
(SEDs) of z ~ 6-7 LAEs for the first time. The stacked LAEs have as
blue UV continua as the HST/WFC3 z-dropout galaxies of similar Muv,
but at the same time they have red UV-to-optical colors with detection
in the 3.6um band. Using SED fitting we find that the stacked LAEs
have low stellar masses of ~ (3-10) x 10^7 Msun, very young ages of ~
1-3 Myr, negligible dust extinction, and strong nebular emission from
the ionized ISM, although the z=6.6 object is fitted similarly well
with high-mass models without nebular emission; inclusion of nebular
emission reproduces the red UV-to-optical color while keeping the UV
color sufficiently blue. From the minimum contribution of nebular
emission required to fit the observed SEDs, we place an upper limit on
the escape fraction of ionizing photons to be f_esc ~ 0.6 at z=5.7 and
~ 0.9 at z=6.6.
連絡先
名前：小林正和,
備考
テレビ参加不可
12月24日(金)
キャンパス
三鷹
セミナー名
VLBIコロキウム
臨時・定例の別
定例
日時
12月24日（金曜日）15時～16時
場所
南研2階VLBIセミナー室
講演者
新沼浩太郎
所属
水沢VLBI観測所
タイトル
The Quick Follow-up Observation of the Largest X-ray Flare from the TeV
blazar Mrk 421
内容
We carried out the VLBI follow-up observations of the largest X-ray
flare from Mrk 421, which was detected in Feb 16, 2010 with MAXI (ATel
#2444), using the Japanese VLBI Network (JVN) array. It is usually
expected that the delayed increasing of the flux density in the radio
band be seen after the high-energy flare. In order to examine it, a
quick VLBI follow-up observation is essential. Here we report that the
VLBI follow-up observation for the largest flare at the first epoch was
carried out Mar 7, 2010, which is 19 days after the detection of X-ray
flare with MAXI. The observations at the total of five epochs were done
using JVN array at approximately 20-day intervals. Through the follow-up
observation of Mrk 421, a significant radio flux variation was not seen.
We discuss an adiabatic expansion loss by setting an upper limit on the
decay time from radio observations in my talk.