第177回: 2011/05/19(木) 15:30-16:30†
田村 陽一 氏 (東京大学・天文学教育研究センター)
「ASTE搭載用超伝導転移端センサ型ボロメータカメラとALMA初期科学運用」
"The new TES bolometer camera for ASTE and the ALMA early science operation"
東京大学天文センター・国立天文台・北海道大学は、チリ・アタカマ砂漠に設置された
ASTE望遠鏡への搭載を目的とした超伝導転移端センサ型ボロメータカメラ開発を、
2009年より推進している。本カメラは本年7月にASTE望遠鏡に搭載され、1100、850ミクロン
（将来的には450ミクロンも）における地上天文観測を開始する予定だ。
その観測対象は、遠方銀河・銀河団、ガンマ線バースト、マゼラン雲、原始惑星系円盤と
多岐にわたる。本講演の前半では、ASTE観測所の現状、本サブミリ波カメラプロジェクトの
サイエンスケース、および進捗を紹介する。
本講演の後半では、いよいよ開始されるALMAの初期科学運用に触れたい。
3月末に観測提案公募の情報が、のべ100ページに迫る複数の文書とともに公表された。
この公募の独特な点は、世界各国の電波天文学者の注目の高さもさることながら、
観測提案者・提案内容に課せられた条件の多さにあると言える。ひとりのユーザの視点から、
初期運用フェイズのALMAの性能・観測公募の内容を読み解きたい。
第178回: 2011/06/16(木) 15:30-16:30†
Michael Richmond 氏 (Rochester Institute of Technology)
"Looking for eclipsing RR Lyr stars in the MACHO database"
The MACHO Project collected photometry of many RR Lyrae stars from its observations of the Milky Way's bulge.
We examined the lightcurves of 3256 stars identified as RRab Lyr variables by Kund et al. 2008,
subtracting an empirical model of the pulsation lightcurve and searching for periodic variation in the residuals.
There are no systems which show the brief dips in light characteristic of detached eclipsing binary systems.
We discuss the results for objects which show the largest residual periodic modulation,
most of which are probably due to aliases of the fundamental period.
(See http://arxiv.org/abs/1106.0697.)
第179回: 2011/06/30(木) 15:30-16:30†
田中 賢幸 氏 (東京大学・IPMU)
"A new method to identify AGNs and the nature of low-luminosity AGNs"
We develop a new method to identify AGNs using optical spectra of galaxies.
The newly developed method is fairly sensitive to low-luminosity AGNs and
also it allows us to cleanly subtract emission line fluxes due to star formation
and extract pure AGN emission, which is crucial to characterize AGN activities.
We study the nature of the identified low-luminosity AGNs with black hole masses,
accretion rates and host galaxy properties.
Our findings include
(1) AGNs reside in massive galaxies (>1010 M_sun),
(2) accretion rates increase with increasing host galaxy star formation rates, and
(3) black hole growth rates increase with increasing host galaxy growth rates.
We discuss implications of these findings for the BH-galaxy co-evolution.
第180回: 2011/07/07(木) 15:30-16:30†
橋本 哲也 氏 (国立天文台)
"A hint of AGN feedback: Shock heating of ISM induced by a jet in NGC 1068"
We present J-band long-slit spectroscopic observation of
NGC 1068 classified as a Seyfert 2 galaxy. J-band observations
with OAO/ISLE provide clear detection of spatially extended [Fe II]1.257um
and [P II]1.188um lines. We found that [Fe II]1.257um/[P II]1.188um
increases with distance from a central continuum peak. Observed line
ratios around the nucleus (continuum peak) are consistent with a typical
value expected from photoionization models, while the ratios at
3 arcsec - 4 arcsec (210-280 pc) east and west of the nucleus
are slightly higher than this. In the off nucleus region of NGC 1068
we also found a possible association between [Fe II]1.257um/[P II]1.188um
and the radio continuum. This suggests a mild contribution of shock
ionization induced by a radio jet outside nucleus while photoionization by
the central energy source is dominant near the nucleus. This result is
a hint to investigate the on going site where the AGN activity inputs
its energy to surrounding interstellar medium (ISM) through a shock heating
induced by a jet. This kind of energy input into ISM may be the
key to reveal a recently emerged serious problem that theoretical simulations
predict too many massive galaxies due to long-duration star formations in
contrast to early-time quenching of star formation in observed massive galaxies,
and may be also closely correlated with the co-evolution of super massive black
hole and its host galaxy. We also present preliminary result of J-band integral
field unit spectroscopy (NIFS+AO) of narrow line region in NGC 1275.
第181回 2011/07/21(木) 15:30~16:30†
柏川 伸成 氏 (国立天文台)
「AKB48 vs. NMB48 vs. SKE48, そして LAE45vs.LAE54」
"Completing the Census of Lyα Emitters at the Reionization Epoch"
We carried out extended spectroscopic confirmations of Lyα emitters (LAEs) at z = 6.5 and 5.7
in the Subaru Deep Field. Now, the total number of spectroscopically confirmed LAEs is 45 and 54
at z = 6.5 and 5.7, respectively, and at least 81% (70%) of our photometric candidates
at z = 6.5 (5.7) have been spectroscopically identified as real LAEs.
We made careful measurements of the Lyα luminosity, both photometrically and spectroscopically,
to accurately determine the Lyα and rest-UV luminosity functions (LFs).
The substantially improved evaluation of the Lyα LF at z = 6.5 shows an apparent deficit
from z = 5.7 at least at the bright end, and a possible decline even at the faint end,
though small uncertainties remain. The rest-UV LFs at z = 6.5 and 5.7 are in good agreement,
at least at the bright end, in clear contrast to the differences seen in the Lyα LF.
These results imply an increase in the neutral fraction of the intergalactic medium
from z = 5.7 to 6.5. The rest-frame equivalent width (EW_0 ) distribution at z = 6.5
seems to be systematically smaller than z = 5.7, and it shows an extended tail toward larger EW_0 .
The bright end of the rest-UV LF can be reproduced from the observed Lyα LF and a reasonable
EW_0 -UV luminosity relation. Integrating this rest-UV LF provides the first measurement of
the contribution of LAEs to the photon budget required for reionization. The derived UV LF
suggests that the fractional contribution of LAEs to the photon budget among Lyman break galaxies
significantly increases toward faint magnitudes. Low-luminosity LAEs could dominate
the ionizing photon budget, though this inference depends strongly on the uncertain
faint-end slope of the Lyα LF.
第182回 2011/07/28(木) 15:30~16:30†
上塚 貴史 氏 (東大・天文センター)
"Mid-infrared spectral monitoring toward AGB stars - Probing the formation of circumstellar dust - "
Asymptotic giant branch (AGB) stars are the stars in the final evolutionary stage of low-
and intermediate-mass stars. They are known to show mass-loss events caused by their stellar wind,
and the events play an important role for chemical evolution of the universe.
The stellar wind is thought to be driven by radiative pressure on dust formed around the central star.
After the grains are formed, they are accelerated by the radiation from inner region,
and the gaseous material is accelerated by the gas-dust collisions.
This scenario has not been fully investigated by observations. It is important to probe
when, where and what kind of grains are formed around the region where the stellar wind is driven,
and mid-infrared spectral monitoring is one of useful methods.
As an example, I will present our monitoring observation toward HV2446 and IRAS04544-6849,
which are Mira type variables in the Large Magellanic Cloud, taken with Spitzer Space Telescope.
Both objects showed time variation of silicate features. These variations can be explained
mainly by the temperature variation caused by the luminosity variation of the central star.
However, the strength and the shape of the feature around the visual maximum phase cannot be
explained by this effect. This suggests possibility of the dust formation around this phase.
From this result, the monitoring observations are thought to have big potential to probe the grain formation events.
In this talk, I will discuss about this result and the usefulness of long-term monitoring observations with mini-TAO and TAO.
第183回: 2011/10/06(木) 15:30-16:30†
眞山 聡 氏 (総研大)
「すばる+ALMA及びコンピュータシミュレーションで探る連星系原始惑星系円盤」
"Subaru + ALMA Observations and numerical simulations of Protoplanetary Disks in a Young Multiple star"
Protoplanetary disks afford a key to an understanding of the formation of our Solar System
and other planetary systems. They are the ingredients of planets and play important roles
in early stellar evolution. If a forming star with a protoplanetary disk has close companions,
the disk may be seriously influenced. This effect should not be ovelooked
because most stars form as multiples. Studies of protoplanetary disks in multiple systems are
thus important to unravel the general process of star and planet formation.
From this point of view, we conducted Subaru direct observations of protoplanetary disks
in multiple systems. High angular resolution near-infrared adaptive optics images of
young binaries were obtained with the infrared camera Coronagraphic Imager
with Adaptive Optics mounted on the 8.2m Subaru Telescope. Our 0."1 resolution images
resolve complex circumstellar structures around binary systems. We present our observational
result as well as 2D and 3D numerical simulations which reproduce accretion onto the binary system.
Additionally, our observational future plans of multiple protoplanetary disks using ALMA will be introduced.
第184回: 2011/10/13(木) 15:30-16:30†
Gaston Folatelli 氏 (東京大学・IPMU)
"What spectra reveal of Type Ia Supernovae"
I will address the importance of Type Ia supernovae (SNe Ia) as astrophysical objects,
and also as distance indicators for cosmology. Based on data from the Carnegie Supernova
Project (CSP), I will describe how precision distances are obtained, with a detailed characterization
of reddening. The role of optical spectroscopy in improving our understanding of the physical
nature of these events will be addressed. In particular, I will show a recent finding of unburned
material in a significant fraction of SNe Ia, and its implications on explosion physics.
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