Home > Archives > 2013-11

2013-11

Investigating the coevolution between SMBHs and galaxies at z~3 etc.

[Speaker 1]
Yuriko Saito
D1, SOKENDAI, Hawaii(supervisor : Masatoshi Imanishi)
[Title]
Investigating the coevolution between SMBHs and galaxies at z~3
-our first result-
[Abstract]
In the local universe, there is a tight correlation between the masses
of super massive black holes (SMBHs) and stars in the spheroidal
components (bulge and elliptical galaxies), suggesting that their formation
is physically closely related. Various models assuming different physical
mechanisms are proposed to explain the observational result at z=0.
Since these models predict different redshift evolution of the
SMBH-spheroid mass ratio, it is important to observationally constrain
the mass ratio at high redshift. As the predicted difference becomes
larger at higher redshift, going to higher redshift is better to distinguish
among these models, but at the same time observational difficulties
increase at higher redshift. By taking into account these factors,
we have concluded that z=3-3.5 is practically the best redshift range.
However, previous studies have mostly been limited to z<2. We have embarked on (1) systematic near-infrared spectroscopy of z=3-3.5 QSOs, to derive the SMBH masses, based on the the Balmer beta emission line width and nearby continuum luminosity, and (2) Subaru LGS-AO near-infrared multi-color imaging observations, to estimate spheroidal stellar masses in the host galaxies of these QSOs. We obtained spectroscopic data for 34 objects, and succeeded to derive BH masses for 24 objects among them. We have also performed Subaru AO imaging observations of 8 QSOs with estimated SMBH masses, and so far completed AO imaging data analysis of J0725. In this talk, I will present our first result of SMBH mass – bulge mass ratio calculated for J0725. [Speaker 2] Shogo Ishikawa M2, SOKENDAI, Mitaka(supervisor : Nobunari Kashikawa) [Title] The clustering properties of star-forming galaxies at z~2 by extremely wide-field survey [Abstract] One of the most critical method to trace the evolution history of galaxies is to compare the mass of dark haloes. Dark halo mass monotonically grows by merging with cosmic time、 so this parameter reflects the growing history of galaxy directly. In recent years, a number of LBGs/LAEs at z>3 are obtained and dark halo masses of z>3 galaxies are revealed.
On the other hand, dark halo masses at z~2 is not so much explored because there are technical difficulties to observe galaxies at z~2. That is why z~2 is known as “redshift-desert”; however, z~2 is also thought to be a important era to study galaxy formation and evolution.
We conducted the wide field survey to obtain star-forming galaxies at z~2, applying so called “BzK selection technique”. In this talk, we report the results of clustering analysis of star-forming galaxies at z~2. Especially, we performed the full HOD analysis of z~2 galaxies the first in the world.

Environmental Dependence of Star Formation in Nearby Barred Spiral Galaxies etc.

[Speaker 1]
Pan Hsi-An
   D3, SOKENDAI, Nobeyama(supervisor : Nario Kuno)
[Title]
Environmental Dependence of Star Formation in Nearby Barred Spiral Galaxies
[Abstract]
I will introduce environmental dependence of star formation in terms of two aspects: amount of gas and the possible dynamical influence from galactic bar.

[Speaker 2]
Jun Toshikawa
   D2, SOKENDAI, Mitaka(supervisor : Nobunari Kashikawa)
[Title]
Complete Follow-up Spectroscopy of a Protocluster at z~6
[Abstract]
In the local universe, galaxy clusters play central roles in the large-scale structure of the universe, and such high-density environments have large effects on galaxy properties. For understanding the structure formation and galaxy evolution, it is crucial to directly investigate the progenitors of galaxy clusters. Galaxy protoclusters are overdense regions in the early universe and considered to grow into rich clusters
seen in the present-day universe. Therefore, protoclusters provide a great deal of information of early stage of cluster formation for large-scale structure and environmental effects.
We showed our discovery of a z~6 protocluster in the Subaru Deep Field in the previous colloquium (Toshikawa et al. 2012, ApJ, 750, 137). And then, we have carried out deeper and wider follow-up spectroscopy of this protocluster than previous ones. All candidates of protocluster galaxies were observed with long exposures, and spectroscopic survey was extended to surrounding region to seek the large-scale structure. In the colloquium, we present the results of the follow-up spectroscopy of the protocluster and discuss galaxy distribution and properties at this first site of galaxy cluster formation.

Review of Spronck et al.2013: Fiber Scrambling for High-Resolution Spectrograph etc.

[Speaker 1]
Haruka Babab
M1, SOKENDAI, Mitaka(supervisor : Wako Aoki)
[Title]
Review of Spronck et al.2013: Fiber Scrambling for High-Resolution Spectrograph
[Abstract]
One of the goals of studying exoplanets is to find “second-Earth”. The Kepler space telescope has found more than 3000 exoplanets candidates including several times Earth-mass planets, but they are too far form our solar system to observe more further. Detection of such planets around G-type stars is very difficult because of the accuracy, so detection around M-type stars which exist a lot in neighborhood has been planned. In order to find such planets in the Habitable Zones near our solar system, infrared high-resolution spectrographs have been developed by some groups, because M-type stars are bright in the infrared wavelength region. IRD -Infrared Doppler- is one of such spectrographs, developed for Subaru telescope. IRD uses optical fibers to couple the telescope to spectrograph. This paper, Spronck et al.2013, demonstrated an improvement in the stability of the instrumental profile using the fiber scrambler. Additionally, they presented data obtained with a double scrambler that further improves the stability of the instrument

[Speaker 2]
Akimasa Kataoka
D2, SOKENDAI, Mitaka(supervisor : Kohji Tomisaka)
[Title]
Planetesimal formation via fluffy aggregates
[Abstract]
To understand the structure evolution of dust aggregates is a key in the planetesimal formation. Dust grains become fluffy by coagulation in protoplanetary disks. However, once they become fluffy, they are not sufficiently compressed by collisional compression to form compact planetesimals (Okuzumi et al. 2012, ApJ, 752, 106). Thus, some other compression mechanisms are required to form planetesimals.
We investigate the static compression of highly porous aggregates. First, we derive the compressive strength by numerical N-body simulations (Kataoka et al. 2013a, A&A, 554, A4). Then, we apply the strength to protoplanetary disks, supposing that the highly porous aggregates can be quiasi-statically compressed by ram pressure of the disk gas and the self gravity. As a result, we find the pathway of the dust structure evolution from dust grains via fluffy aggregates to compact planetesimals. Moreover, we find that the fluffy aggregates overcome the barriers in planetesimal formation, which are radial drift, fragmentation, and bouncing barriers (Kataoka et al. 2013b, A&A, 557, L4).

Home > Archives > 2013-11

Search
Feeds

Return to page top