Investigating the coevolution between SMBHs and Galaxies at z~3 / Morphological Evolution of Passively Evolving Early-type Galaxies at z~2

[Speaker 1]
Yuriko Saito
Investigating the coevolution between SMBHs and Galaxies at z~3
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. Since 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 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, using 3--4m telescopes, and (2) Subaru LGS-AO near-infrared multi-color imaging observations, to estimate spheroidal stellar masses in the host galaxies of these QSOs. The use of Balmer beta line, PSF-stable Subaru LGS-AO, and multi-color imaging data make our study the most reliable and promising to investigate the redshift evolution of SMBH-spheroid mass ratio and to observationally constrain the physical mechanism behind the correlation. In this talk, I will present our strategy and current progress of this project. ------------------------------------------------------------ ------------------------------------------------------------ [Speaker 2] Sumire Tatehora [Title] Morphological Evolution of Passively Evolving Early-type Galaxies at z~2 [Abstract] Understanding the formation of massive elliptical galaxies is an unsolved problem. The discovery of a widespread population of passively evolving early-type galaxies (ETGs) at z>1.4 have proved that quenching star formation in most massive galaxies was well under way by z~2. And such objects are extremely compact, having much smaller effective radii compared to local ETGs with the same stellar mass, while massive ETGs
with similar effective radii have also been found. If we understand their dynamical and structural properties in detail, it is important to measure the stellar velocity dispersion of galaxies. However the number of high-z ETGs with measurement of the velocity dispersion is still extremely small.
So we have deep NIR spectroscopic observations of 33 massive passive BzK-selected galaxies (pBzKs) from the COSMOS field using Subaru/MOIRCS. In this talk, I will present progress of an analysis.