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K(2 m) Version of JASMINE and its Science. Advantage in Bulge Science and Potential By-products from Idle Time T. Nakajima (NAOJ). Demand from Instrumentation. Radiation cooling at L2 point sets telescope environmental temperature down to about 50K.
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K(2 m) Version of JASMINEand its Science Advantage in Bulge Science and Potential By-products from Idle Time T. Nakajima (NAOJ)
Demand from Instrumentation • Radiation cooling at L2 point sets telescope environmental temperature down to about 50K. • Since the operating temperature of CCDs is about 150K, they must to warmed up!----- Detectors are heat sources. • The operating temperature of HgCdTe NIR arrays is about 70K. Better matching with environmental temperature.
Abstract of K (2 m) Science • Main advantage of JASMINE-K • A. astrometric accuracy of Bulge stars with Av>6 is better compared with that at z band (0.9 m). • B. Since, AZ ~ 4 AK , QSO/AGN count is much greater at K. They behave as fixed positional references. • By-products • More than 1 / 4 of the mission period should be used for other purposes such as NIR deep survey due to the Bulge-Sun coincidence. • At high Galactic latitudes, the limit of galaxy count is set by confusion to K = 24 ~ 25. • An example of science program: A search for QSOs beyond z = 7.
Main advantages for bulge stars • Bulge Giants • Intrinsic SEDs are red. • Combining the SED and extinction, astrometric error given by σ~ /D/√N, is smaller at K than z for Av > 6. • Background QSO count • If we estimate the QSO number count in JASMINE field of 200 sq. deg from extinction-free high latitude QSO counts, a meaningful number of them are expected. • Identification of these QSOs prior to the mission, and long-exposures of these QSO fields at the mission will necessary.
Relative astrometric accuracy of Bulge giants between z and K K is better if σz/σK>1.
Range of QSO countin 200 sq deg JASMINE field • Assumptions: Av=0. fν~ ν-1 for QSOs. • UV – excess selected quasars (large U-B, or u-g) • PG quasars w/ correction n(K<11.8) < 3.4. • LBQS n(K<14) ~ 200, n(K<13)~125, n(K<12) ~ 3. • Fainter and more distant QSOs from SDSS • Including narrow-line QSOs/AGNs • n(K<13.8) > 4.0. (SDSS misses brightest ones.) • Variability selection • n(K<15.4) ~ 1000 (SDSS, σvar > 0.03 mag) • n(K<16.3) > 400 (MACHO,LMC,+color)
Extragalactic astronomy during the idle time of Bulge observations • How to utilize 1 / 4 of astrometry idle time? • Taking advantage of a wide FOV (0.7x0.7deg). • Advantage of NIR imaging from space. • The zodiacal background has its minimum in NIR, since its a valley between scattered Sun light in the visible and thermal dust emission in MIR. • Telescope thermal emission is negligible at L2. • Re-ionization era (z=10~17) can be probed at rest-frame UV at K band.
Sensitivity at K (Point source) Age of Univ. rest (m) Lrest (Lsun)
Sky at K (Vega) > 23 • Cumulative galaxy count (Eg. Minowa et al. 2006) • 1 galaxy in 10 square arcsec. (1 in 3”x3”) at K~23. • Since galaxies are extended, better resolution (larger telescope) does not necessarily remedy the confusion problem. --- there may be more than one galaxy for each line of sight at K>25. • In one quarter of the mission life of JASMINE, 5,000 ~ 10,000 sq. deg. will be surveyed.
Conceivable New Science Programs • QSO/AGN survey up to z ~ 13 (H dropout). • My empirical number count estimation in 10,000 sq. deg. • 3 for M145 < -26 (1012 Lsun) between z=10 & 13. • 6 for M145 < -25 (3x1011 Lsun) between z=10 & 13. • Foreground ISM study or locating high density regions. • Wide-filed galaxy count down to K=24 and/or • Extragalactic NIR background radiation, if superposition of faint galaxies is inevitable.
