Fast photon detectors will be one of the key technologies to introduce new observing methods. Utilizing our recent development of low leakage SIS junctions with Nb/Al/AlOx/Al/Nb, we designed and ...fabricated an antenna-coupled SIS detector. The detector exhibited a leakage current of 2 pA at
T
≤
0.8
K
. Fourier transform spectrometer measurements show a clear resonance peak, although the peak frequency and bandwidth were shifted from the designed values. Even though the detector efficiency was low, the noise measurement suggests that the detector would allow us to read out single terahertz photon by introducing the photon-counting scheme.
Recent developments on the detector and the cryogenics for the terahertz photon detector system are discussed. The detector has been redesigned for improved performance, which exhibited optical ...efficiency of 6% at 530 GHz. Cryogenics for the detector system has been newly developed which employs a pulse-tube cooler with two originally developed compact
4
He sorption fridges. Initial experiments demonstrated continuous cooling by altering operation of two sorption fridges, supported by a pulse-tube cooler with cooling power of 0.4 W.
For astronomical observation at terahertz frequencies, a variety of cryogenic detector technologies are being developed to achieve background-limited observation from space, where a noise equivalent ...power (NEP) of less than
10
-
18
W/Hz
0.5
is often required. When each photon signal is resolved in time, the requirements on NEP are reduced and 1 ns time resolution corresponds to an NEP of approximately
10
-
17
W/Hz
0.5
at THz frequencies. Furthermore, fast photon counting detectors have a high dynamic range to observe bright terahertz sources such as stars and active galactic nuclei. Applications of photon counting detector are discussed for cosmic microwave background and photon counting terahertz interferometry.
We present the results of a blind millimeter line emitter search using ALMA Band 6 data with a single-frequency tuning toward four gravitational lensing clusters (RXJ1347.5−1145, Abell S0592, MACS ...J0416.1−2403, and Abell 2744). We construct 3D signal-to-noise ratio (S/N) cubes with 60 and 100 MHz binning, and search for millimeter line emitters. We do not detect any line emitters with a peak S/N > 5, although we do find a line emitter candidate with a peak S/N 4.5. These results provide upper limits to the CO(3−2), CO(4−3), CO(5−4), and C ii luminosity functions at z 0.3, 0.7, 1.2, and 6, respectively. Because of the magnification effect of gravitational lensing clusters, the new data provide the first constraints on the CO and C ii luminosity functions at unprecedentedly low luminosity levels, i.e., down to 10−3 - 10−1 Mpc−3 dex−1 at K km s−1 pc2 and 10−3-10−2 Mpc−3 dex−1 at , respectively. Although the constraints to date are not yet stringent, we find that the evolution of the CO and C ii luminosity functions are broadly consistent with the predictions of semi-analytical models. This study demonstrates that the wide observations with a single-frequency tuning toward gravitational lensing clusters are promising for constraining the CO and C ii luminosity functions.
An Intensity interferometer with photon counting detector is a candidate to realize a THz interferometer for astronomical observations. We have demonstrated that synthesis imaging is possible even ...with intensity interferometers. An SIS junction (or STJ) with low leakage current of 1 pA is a suitable device for photon counting detectors. Readout circuit utilizing FETs with low gate leakage, low gate capacitance, and fast response is discussed.
Abstract
We present a high-sensitivity (1
σ
< 1.6 mJy beam
−1
) continuum observation in a 343 arcmin
2
area of the northeast region of the Small Magellanic Cloud at a wavelength of 1.1 mm, ...conducted using the AzTEC instrument on the ASTE telescope. In the observed region, we identified 20 objects by contouring 10
σ
emission. Through spectral energy distribution analysis using 1.1 mm,
Herschel
, and
Spitzer
data, we estimated gas masses of 5 × 10
3
–7 × 10
4
M
⊙
, assuming a gas-to-dust ratio of 1000. The dust temperature and index of emissivity were also estimated as 18–33 K and 0.9–1.9, respectively, which are consistent with previous low-resolution studies. The dust temperature and the index of emissivity shows a weak negative linear correlation. We also investigated five CO-detected, dust-selected clouds in detail. The total gas masses were comparable to those estimated from the Mopra CO data, indicating that the assumed gas-to-dust ratio of 1000 and the
X
CO
factor of 1 × 10
21
cm
−2
(K km s
−1
)
−1
, with uncertainties of a factor of 2, are reliable for the estimation of the gas masses of molecular or dust-selected clouds. The dust column density showed good spatial correlation with CO emission, except for an object associated with bright young stellar objects. The 8
μ
m filamentary and clumpy structures also showed a spatial distribution similar to that of the CO emission and dust column density, supporting the fact that polycyclic aromatic hydrocarbon emissions arise from the surfaces of dense gas and dust clouds.
ABSTRACT
The first 1.1 mm continuum survey toward the Small Magellanic Cloud (SMC) was performed using the AzTEC instrument installed on the ASTE 10 m telescope. This survey covered 4.5 deg
2
of the ...SMC with 1
σ
noise levels of 5–12 mJy beam
−1
, and 44 extended objects were identified. The 1.1 mm extended emission has good spatial correlation with
Herschel
160
μ
m, indicating that the origin of the 1.1 mm extended emission is thermal emission from a cold dust component. We estimated physical properties using the 1.1 mm and filtered
Herschel
data (100, 160, 250, 350, and 500
μ
m). The 1.1 mm objects show dust temperatures of 17–45 K and gas masses of 4 × 10
3
–3 × 10
5
M
⊙
, assuming single-temperature thermal emission from the cold dust with an emissivity index,
β
, of 1.2 and a gas-to-dust ratio of 1000. These physical properties are very similar to those of giant molecular clouds (GMCs) in our galaxy and the Large Magellanic Cloud. The 1.1 mm objects also displayed good spatial correlation with the
Spitzer
24
μ
m and CO emission, suggesting that the 1.1 mm objects trace the dense gas regions as sites of massive star formation. The dust temperature of the 1.1 mm objects also demonstrated good correlation with the 24
μ
m flux connected to massive star formation. This supports the hypothesis that the heating source of the cold dust is mainly local star-formation activity in the 1.1 mm objects. The classification of the 1.1 mm objects based on the existence of star-formation activity reveals the differences in the dust temperature, gas mass, and radius, which reflects the evolution sequence of GMCs.
We present a new on-the-fly mapping of CO (J = 3-2) line emission with the Atacama Submillimeter Telescope Experiment toward the 8' X 8' (or 10.5 X 10.5 kpc at the distance of 4.5 Mpc) region of the ...nearby barred spiral galaxy M 83 at an effective resolution of 25''. Due to its very high sensitivity, our CO (J = 3 - 2) map can depict not only spiral arm structures but also spur-like substructures extended in inter-arm regions. This spur-like substructures in CO (J = 3-2) emission are well coincident with the distribution of massive star-forming regions traced by H Delta *a luminosity and Spitzer/Infrared Array Camera 8 Delta *mm emission. We have identified 54 CO (J = 3-2) clumps as Giant Molecular-cloud Associations (GMAs) employing the CLUMPFIND algorithm, and have obtained their sizes, velocity dispersions, virial masses, and CO luminosity masses. We found that the virial parameter Delta *a, which is defined as the ratio of the virial mass to the CO luminosity mass, is almost unity for GMAs in spiral arms, whereas there exist some GMAs whose Delta *a are 3-10 in the inter-arm region. We found that GMAs with higher Delta *a tend not to be associated with massive star-forming regions, while other virialized GMAs are. Since Delta *a mainly depends on velocity dispersion of the GMA, we suppose that the onset of star formation in these unvirialized GMAs with higher Delta *a are suppressed by an increase in internal velocity dispersions of giant molecular clouds within these GMAs due to shear motion.
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