An extremely dense group of massive galaxies at the centre of the protocluster at z=3.09 in the SSA22 field

Transcription

1 An extremely dense group of massive galaxies at the centre of the protocluster at z=3.09 in the SSA22 field 2015/9/7-11 In the Footsteps of Mariko Kuob (ICRR Univ Tokyo), Toru Yamada, Takashi Ichikawa (Tohoku University), Masaru Kajisawa (Ehime Univ), Yuichi Matsuda, Ichi Tanaka (NAOJ), Hideki Umehata (ESO, Univ Tokyo)

2 Abstract A very dense group of galaxies is identified at the center of the protocluster at z=3.09 from the NIR spectroscopy. The velocity dispersion of this group implies that this group is bound to an object >10^13 M_sun Compared with the galaxy formation models based on the Millennium simulation, the AzTEC14 group is plausibly hosted within the halo with mass ~10^14 M_sun. They plausibly evolve into a BCG at the center of one of the most massive clusters.

3 1. INTRODUCTION Meza+05 Formation of massive galaxies via hierarchical multiple merger is predicted in cosmological numerical simulations. Any direct observational evidence of multiple mergers at high-z?? Boyalan-Kolchin+2009

4 On-going multiple mergers in the SSA22 protocluster at z=3.09? 40% of LABs in the SSA22 have two or more counterparts with z_phot= (Uchimoto+12)

5 2. Observation Targets: K-selected (K<24) counterparts with z_phot= or DRGs (J-K>1.4) Dates: 2012/9-10, 2014/6(7 but bad condition) (Kubo et al and submitted) Instruments: MOIRCS (Subaru) with HK500 or VPH- K (R~1700) grisms EXPTIME=13-20 ksec per mask PSF sizes: σ limit = 0.6-1x10^{-17} erg/s/cm^2 For the SED fitting and stellar mass estimate ubvri z JHK+IRAC imaging data are used

6 3.Results AzTEC14 Red circles: z_spec= Black circles: z_phot~3.1 Yellow contours: Lyα Isophotal area LAB12 LAB01 150kpc LAB galaxies are confirmed in each object LAB30 Kubo+submitted

7 The AzTEC14 group at an ASTE/AzTEC 1.1mm source 7 galaxies witin 120 kpc, 60 times denser than the protocluster itself 5 have M*>10^10.5 M_sun Total stellar mass ~5x10^11 M_sun Multiple SMGs are resolved with ALMA (Umehata et al. in prep) z_spec=3.09 Kubo+submitted z_phot~3.1 ALMA 263 GHz

8 Line-of-sight velocity distribution AzTEC14 group is bound to object with >10^13M_sun LABs are bound to objects with >10^10.5 M_sun

9 4.Discussion What the groups are? comparing with the cosmological simulations selecting the comparison groups of the AzTEC14 group and LABs from the galaxy formation models based on the Millennium simulation

10 The AzTEC 14 group Consisting from 5 galaxies with >4x10^10 M_sun (stellar mass completeness limit) within 120 kpc In the Millennium simulation, such groups are found at the center of virialized halos with M_H=10^13.9M_sun (De Lucia et al and Guo et al. 2010) at z=3.06 snapshots Since there is only one comparison group at z=3.06 in the full Millennium, we also select the comparison group by rescaling the local groups median M_H=10^13.9 M_sun The comparison group at z=3.06 evolves into a BCG while the background halos become ten times massive at z=0 LAB01 and LAB30 2 galaxies with >3x10^10 M_sun within 60-80kpc Halo mass of the comparison groups ranging from M_H~10^12.6 to 14.0 M_sun

11 Velocity distribution of the AzTEC14 group agree well with the simulation. Stellar mass function of the groups agree well with the simulation at least M*>10^10.5 M_sun ( In 6, about lower stellar mass )

12 K15c Stellar population of the AzTEC14 group K15a Kubo et al The SEDs of the most massive galaxy Az14-K15c and -K15a are fitted with those of quiescent galaxies with age=2 Gyr and 0.5 Gyr, respectively. -K15a is also an AGN detected in X-ray (Lehmer et al. 2009). ALMA sources (-K15b and -K15e)

13 5. Deep and high resolution imaging with AO of the AzTEC14 group ( preliminary) What are their morplogies? Stellar mass function at low mass end? Deep imaging in K -band with adaptive optics IRCS with AO188 on Subaru telescope 2015 July (PI Kubo)

14 AO corrected PSF size ~0.15 & EXPTIME~3 hours K15a K15b K15c K15d Preliminary K15e K15f md048 b+d+e+f (24kpc) The most massive quiescnet galaxy Az14-K15c is fitted with Sersic index n=2.94±0.27 and Re=1.16±0.6 kpc, AzTEC14-K15a is fitted with n=7.70±3.63 and Re=0.84±0.28 kpc Support the scenario that massive ellipticals evolved from compact ellipticals via mergers

15 K -band source count (preliminary, no photo-z selection) with the detection limit K =25.5 (0.3 aperture) Dashed line: source count Preliminary of field w AO, normalized to the spatial extent of the AzTEC14 group MOIRCS drops at K=24 due to the detection limit (in stellar mass ~4x10^10M_sun) IRCS AO drops below the detection limit(~10^10m_sun) Difficiency of low mass satellites?

16 6. Conclusion A very dense group of galaxies is identified at the center of the protocluster at z=3.09 The velocity dispersion of this group implies that this group is bound to an object >10^13 M_sun Compared with the galaxy formation models based on the Millennium simulation, the AzTEC14 group is plausibly hosted within the halo with mass ~10^14 M_sun. They plausibly evolve into a BCG at the center of one of the most massive clusters. Star formation of some members are quenched while some are dusty starburst galaxies. Preliminary Massive quiescent member is a compact elliptical. There is a deficiency of low mass galaxies <10^10.5M_sun