ALMA 時代の宇宙の構造形成理論：第 1 世代から第 n 世代へ 2013 年 1 月 28 日 北海道大学 すばる /FMOS で探る z~1.4 付近の星形成銀河 矢部清人 ( 国立天文台 ) NIR Spectroscopy of Star-Forming Galaxies at z~1.4 with Subaru/FMOS Kiyoto Yabe (NAOJ) Collaborators: Kouji Ohta, Fumihide Iwamuro, Suraphong Yuma, Masayuki Akiyama, Naoyuki Tamura, and FMOS GTO team
ALMA 時代の宇宙の構造形成理論：第 1 世代から第 n 世代へ 2013 年 1 月 28 日 北海道大学 Introduction: Why Metallicity? • Gas-phase metallicity is a key to understand the galaxy evolution ✓ Heavy elements are synthesized in stars and returned into ISM ✓ Metallicity traces the past star-formation activity ✓ It also changes via gas flow of galaxies ✓ Gas inflow/outflow rate may be able to be constrained Tremonti+2004 • Correlation between stellar mass and metallicity ✓ Firstly reported by Lequeux+1979 for nearby Irr, blue compact galaxies ✓ Massive galaxies tend to show larger metallicity ✓ The mass-metallicity relation is well red line: best-fit established at local universe thanks to the large metallicity SDSS sample (Tremonti+04) ✓ Evolutionary sequence of each galaxy population: Massive galaxies are (chemically) well evolved? stellar mass
ALMA 時代の宇宙の構造形成理論：第 1 世代から第 n 世代へ 2013 年 1 月 28 日 北海道大学 Introduction: Mass-Metallicity Relation at High Redshift • MZ relation at z~2 (e.g., Erb+06) and z~3(e.g.,Maiolino+08) ✓ Evolution of the MZ relation from z~3 to z~0? ✓ Still controversy as to the MZ relation at z~2 (Hayashi+09, Yoshikawa+10, Onodera+10) ✓ We need larger sample at z~2 Maiolino+08 Erb+06 SDSS@z~0.1 0.2-0.3 dex z ~ 2 Metallicity z ~ 2 z ~ 2 Onodera+10 Hayashi+09 Stellar Mass Erb+06 Erb+06 Erb+06 ↑ Sample size ~ 80-90 Sample size ~ 10-20 →
ALMA 時代の宇宙の構造形成理論：第 1 世代から第 n 世代へ 2013 年 1 月 28 日 北海道大学 Introduction: Scatter of the Mass-Metallicity Relation • The MZ relation at z~0.1 has intrinsic scatters (Tremonti+04) • What physical parameters can explain this scatter? +2 σ ✓ SFR (Mannucci+2010), specific SFR (Ellison+2008), +1 σ half light radius (Ellison+2008), galaxy interaction (Rupke+2008) -1 σ -2 σ • The intrinsic scatter of the MZ relation at high-z is still unknown • We need large sample at high-z Tremonti+2004 Mannucci+2010 lower SFR higherSFR Intrinsic scatter deviation from best-fit Metallicity Metallicity Stellar Mass Stellar Mass
ALMA 時代の宇宙の構造形成理論：第 1 世代から第 n 世代へ 2013 年 1 月 28 日 北海道大学 Introduction: Why z=1-2? • z=1-3 is dramatic and violent epoch galaxy evolution in the universe ✓ Global peak or drastic change of various quantities of galaxies ✴ Star formation rate density (global SF activity in the universe) peaked at z~2 ✴ Number density of QSO also peaked at z~2 ✴ Emergence of morphology such as Hubble sequence at z~2 ✓ This is very important phase to understand the galaxy evolution ✓ Spectroscopic nature is difficult to measure at this redshift range (redshift desert) • Emission lines such as H α , H β [NII], [OIII] enter into near-infrared wavelength region ✓ Spectroscopic observations in NIR is time-consuming ✓ Large spectroscopic observations with FMOS on Subaru Telescope Redshift z evolution of QSO number density Star Formation Rate Density z=0 z=1 z=2 z=3 z=5 Morphology of galaxies at z=1-1.5 UV Luminosity Density redshift evolution of SFRD Wolf et al. 2003 Hopkins and Beacom 2006 van Dokkum et al. 2011 Redshift
ALMA 時代の宇宙の構造形成理論：第 1 世代から第 n 世代へ 2013 年 1 月 28 日 北海道大学 Introduction: FMOS on Subaru Telescope • What’s FMOS (Fibre Multi-Object Spectrograph)? ✓ Second generation instrument for Subaru Telescope ✓ Collaboration among Japan, UK, and Australia ✓ Multi-object spectrograph in NIR (0.9-1.8µm) w/ 400 fibers and FoV of 30’ Φ ✓ Low Resolution (LR; R~650) and High Resolution (HR; R~3000) mode ✓ Details are in Kimura et al. 2010, PASJ, 62 , 1135 ✓ We conduct large NIR spectroscopic surveys with FMOS FMOS on the Subaru Telescope Fiber positioner (Echidna) Optical design of FMOS
ALMA 時代の宇宙の構造形成理論：第 1 世代から第 n 世代へ 2013 年 1 月 28 日 北海道大学 Sample Selection and Observations: • Target Sample ✓ Field : SXDS/UDS (effective area~0.7 deg 2 ) ✓ We constructed a K-selected catalogue ✴ z phot , M* are derived from SED fitting ✴ SFR from the rest-frame UV luminosity, E(B-V) from the rest-frame UV color ✴ Expected F(H α ) is from the SFR and E(B-V) ✴ E(B-V) for emission line is derived by using prescription by Cid Fernandes+05 ✓ 1.2<z phot <1.6, K<23.9 AB mag, M * >10 9.5 M sun , F(H α ) exp >5.0x10 -17 cgs ✓ Excluding X-ray sources (L x >10 43 erg/s) ✓ ~5000 objects in whole area of the SXDS 1e-14 10 9.5 M sun • Observations Targeted Objects ✓ Mainly FMOS/GTOs in 2010-2011 Expected H α flux (erg/s/cm 2 ) 1e-15 ✓ LR mode / Cross Beam Switch mode Expected Ha Flux (cgs) ✓ Typical exposure time is 3-4 hrs per FoV ✓ About 1200 objects are observed in total 1e-16 • Data Reduction 5x10 -17 cgs ✓ FMOS reduction pipeline FIBRE-pac 1e-17 ✓ Details are shown in Iwamuro+12 ✓ Fitting methods taking the OH mask 1.2<z phot <1.6 effects into consideration 1e-18 1e+09 1e+10 1e+11 1e+12 Stellar Mass (Msun) Stellar Mass (M sun )
ALMA 時代の宇宙の構造形成理論：第 1 世代から第 n 世代へ 2013 年 1 月 28 日 北海道大学 Observed Spectra: We observed ~1200 targets in total. 5 hrs integration z=1.442 Among them, 343 objects show F(H α )=1.1x10 -16 significant H α emission (S/N>3) at F([NII])=3.8x10 -17 z=1.2-1.6 (median=1.41). This is the FWHM=390 km/s M*=4.6x10 10 M sun largest NIR spectroscopic sample at 12+log(O/H)=8.644 z>1 ever. Shaded area: OH airglow mask z=1.336 3 hrs integration F(H α )=1.5x10 -16 Solid : Observed Spectra F([NII])=3.5x10 -17 FWHM=320 km/s Dashed : Best-fit Model Spectra M*=4.0x10 9 M sun 12+log(O/H)=8.414 Initial results (GTO in 2010; 71 H α detections) are already presented by Yabe+12 (PASJ, 64, 60). In this talk, we also present results from all GTO runs.
ALMA 時代の宇宙の構造形成理論：第 1 世代から第 n 世代へ 2013 年 1 月 28 日 北海道大学 Mass-Metallicity Relation at z~1.4: • Possible AGN candidates are excluded by using BPT diagram • 12+log(O/H) from [NII]/H α line ratio (N2 method; Pettini & Pagel 2004) • No significant [NII] emission (S/N<3.0) from ~70% → Stacking analysis Thick solid line: regression line (this work) The largest sample ever at z>1 Thin solid line: regression line (initial results; Yabe+12)
ALMA 時代の宇宙の構造形成理論：第 1 世代から第 n 世代へ 2013 年 1 月 28 日 北海道大学 Cosmic Evolution of Mass-Metallicity Relation: • Comparison to the previous works up to z~3 ✓ Our results at z~1.4 are between those at z~0.8 and z~2.2 ✓ Anti-downsizing-like evolution from z~1.4 to z~0.8? • Evolution of the MZ relation from z~3 to z~0 ✓ Smoothly evolves from z~3 to z~0 ✓ MZ relation evolution from z~3 to z~0 at fixed stellar masses Cosmic metallicity evolution at fixed stellar mass Metallicity calibration and IMF of other works are all the same as ours
ALMA 時代の宇宙の構造形成理論：第 1 世代から第 n 世代へ 2013 年 1 月 28 日 北海道大学 Comparison with Theoretical Models: • Comparison with theoretical predictions (Davé et al. 2011) ✓ N-body + SPH cosmological simulations (GADGET -2) ✓ 4 wind models (no wind; constant wind; slow wind; mass dependent wind) implemented ✴ Constant wind (cw) : dM wind /dt=2xSFR, v wind =680 km/s ✴ Mass dependent wind (vzw) : velocity dispersion (=mass) dependent wind • Our result generally agrees with cw or vzw models Cosmic metallicity evolution at fixed stellar mass Comparison with Davé+11 no wind slow wind Metallicity calibration and IMF of other works are all the same as ours
ALMA 時代の宇宙の構造形成理論：第 1 世代から第 n 世代へ 2013 年 1 月 28 日 北海道大学 Intrinsic Scatter of Mass-Metallicity Relation: • We found that the MZ relation at z~1.4 has intrinsic scatters of ~0.1 dex ✓ Observational errors are subtracted from the observed scatters ✓ Well agrees with SDSS results at z~0.1 within the error bars ✓ However, note that the values should be lower limit because some metallicities are upper limit, i.e., larger scatters at higher redshift • What is the origin of this scatter? Scatter ( σ ) Thick solid line: regression line (this work) Scatter comparable to z~0 Thin solid line: regression line (initial results; Yabe+12)
ALMA 時代の宇宙の構造形成理論：第 1 世代から第 n 世代へ 2013 年 1 月 28 日 北海道大学 Second Parameter Dependency: • Dependency of SFR and size on the MZ relation ✓ SFR : derived from H α luminosity corrected for the dust extinction ✓ We take half light radius (R 50 ) as galaxy size (from K-band image de-convolving PSF) ✓ Dividing the sample into two groups by the parameter ✓ The dependency of SFR on the MZ relation is not clear ✓ Galaxies with smaller R 50 tend to show higher metallicity SFR(H α ) size (R 50 )
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