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A COSMOLOGICAL PAH SURVEY WITH SPICA
Takehiko Wada,Eiichi Egami,Naofumi Fujishiro,Tomotsugu Goto,Masatoshi Imanishi,Hanae Inami,Daisuke Ishihara,Hidehiro Kaneda,Kotaro Kohno,Yusei Koyama,Hideo Matsuhara,Shuji Matsuura,Tohru Nagao,Youichi 한국천문학회 2017 天文學論叢 Vol.32 No.1
We propose a cosmological survey to probe star formation and nuclear activityin galaxies at redshifts of z = 2 - 4 by polycyclic aromatic hydrocarbon(PAH) features usingthe SPICA mid-infrared instrument (SMI)with a spectral resolution of R = 20. We will cover a wavelength range of 20-36 μmthat corresponds to z = 2 - 4 for the PAH features(11.3, 7.7, and 6.2 μm). The sensitivity will be $1\times10^{-19}$ W/m$^2$ (5 $\sigma$)in case of a referencesurvey that covers 4 arcmin$^2$ field in a one-hour observation. It corresponds to L$_{\rm IR}$=$2\times10^{11}$ $L_\odot$ at z=3and will give us more than 10000 galaxies in a 450 hour survey.
Discovery of a Very Large (≈20 kpc) Galaxy at <i>z</i> = 3.72
Lee, Kyoung-Soo,Dey, Arjun,Matheson, Thomas,Shi, Ke,Hung, Chao-Ling,Xue, Rui,Inami, Hanae,Huang, Yun,Lee, Khee-Gan,Ashby, Matthew L. N.,Jannuzi, Buell,Reddy, Naveen,Hong, Sungryong,Mo, Wenli,Malavasi, American Astronomical Society 2018 The Astrophysical journal Vol.862 No.1
<P>We report the discovery and spectroscopic confirmation of a very large star-forming galaxy, G6025, at z(spec) = 3.721 +/- 0.003. In the rest frame approximate to 2100 angstrom, G6025 subtends approximate to 24 kpc in physical extent when measured from the 1.5 sigma isophote, in agreement with the parametric size measurements that yield a half-light radius of 4.9 +/- 0.5 kpc and a semimajor axis of 12.5 +/- 0.1 kpc. It is also very UV-luminous (approximate to 5L(UV,z similar to 4)*) and young (approximate to 140 +/- 60 Myr). Despite its unusual size and luminosity, the stellar population parameters and dust reddening (M-star similar to M-z similar to 4*( )and E(B - V) similar to 0.18 +/- 0.05) estimated from the integrated light are similar to those of smaller galaxies at comparable redshifts. The ground-based morphology and spectroscopy show two dominant components, both located off-center, embedded in more diffuse emission. We speculate that G6025 may be a scaled-up version of chain galaxies seen in deep HST imaging or, alternatively, a nearly equal-mass merger involving two super-L* galaxies in its early stage. It lies close to but not within a known massive protocluster at z = 3.78. We find four companions within 6 Mpc from G6025, two of which lie within 1.6 Mpc. While the limited sensitivity of the existing spectroscopy does not allow us to robustly characterize the local environment of G6025, it likely resides in a locally overdense environment. The luminosity, size, and youth of G6025 make it uniquely suited to study the early formation of massive galaxies in the universe.</P>
THE 3.3 μm POLYCYCLIC AROMATIC HYDROCARBON EMISSION AS A STAR FORMATION RATE INDICATOR
Kim, Ji Hoon,Im, Myungshin,Lee, Hyung Mok,Lee, Myung Gyoon,Jun, Hyunsung David,Nakagawa, Takao,Matsuhara, Hideo,Wada, Takehiko,Oyabu, Shinki,Takagi, Toshinobu,Inami, Hanae,Ohyama, Youichi,Yamada, Rika IOP Publishing 2012 The Astrophysical journal Vol.760 No.2
<P>Polycyclic aromatic hydrocarbon (PAH) emission features dominate the mid-infrared spectra of star-forming galaxies and can be useful to calibrate star formation rates (SFRs) and diagnose ionized states of grains. However, the PAH 3.3 mu m feature has not been studied as much as other PAH features since it is weaker than others and resides outside of Spitzer capability. In order to detect and calibrate the 3.3 mu m PAH emission and investigate its potential as an SFR indicator, we carried out an AKARI mission program, AKARI mJy Unbiased Survey of Extragalactic Sources (AMUSES), and compared its sample with various literature samples. We obtained 2-5 mu m low-resolution spectra of 20 flux-limited galaxies with mixed spectral energy distribution classes, which yielded the detection of the 3.3 mu m PAH emission from 3 out of 20 galaxies. For the combined sample of AMUSES and literature samples, the 3.3 mu m PAH luminosities correlate with the infrared luminosities of star-forming galaxies, albeit with a large scatter (1.5 dex). The correlation appears to break down at the domain of ultraluminous infrared galaxies (ULIRGs), and the power of the 3.3 mu m PAH luminosity as a proxy for the infrared luminosity is hampered at log[L-PAH3.3 erg(-1) s(-1)] > similar to 42.0. Possible origins for this deviation in the correlation are discussed, including contributions from active galactic nuclei and strongly obscured young stellar objects, and the destruction of PAH molecules in ULIRGs.</P>