Abstract
For submillimeter spectroscopy with ground-based single-dish telescopes, removing the noise contribution from the Earth’s atmosphere and the instrument is essential. For this purpose, here ...we propose a new method based on a data-scientific approach. The key technique is statistical matrix decomposition that automatically separates the signals of astronomical emission lines from the drift noise components in the fast-sampled (1–10 Hz) time-series spectra obtained by a position-switching (PSW) observation. Because the proposed method does not apply subtraction between two sets of noisy data (i.e., on-source and off-source spectra), it improves the observation sensitivity by a factor of
2
. It also reduces artificial signals such as baseline ripples on a spectrum, which may also help to improve the effective sensitivity. We demonstrate this improvement by using the spectroscopic data of emission lines toward a high-redshift galaxy observed with a 2 mm receiver on the 50 m Large Millimeter Telescope. Since the proposed method is carried out offline and no additional measurements are required, it offers an instant improvement on the spectra reduced so far with the conventional method. It also enables efficient deep spectroscopy driven by the future 50 m class large submillimeter single-dish telescopes, where fast PSW observations by mechanical antenna or mirror drive are difficult to achieve.
Analyzing multiband observations of dust continuum emission is one of the useful tools to constrain dust properties that help us to understand the physical properties of the protoplanetary disks. We ...perform a synthetic ALMA multiband analysis to find the best ALMA band set for constraining the dust properties of the TW Hya disk. We find that the Band 10, 6, 3 set is the best set among the possible combinations of ALMA Bands 3, 4, 5, 6, 7, 8, 9, 10. We also find two conditions for the good ALMA band sets providing narrow constraint ranges on dust properties: (1) Band 9 or 10 is included in the band set, and (2) there are enough frequency intervals between the bands. These are related to the conditions that give good constraints on dust properties: the combination of optically thick and thin bands is required, and large β (β is the power-law index of dust opacity, κ ∝ β) and low dust temperature are preferable. To examine our synthetic analysis results, we apply the multiband analysis to ALMA archival data of the TW Hya disk at Bands 4, 6, 7, and 9. The Band 9, 6, 4 set provides the dust properties close to the model profile, while the Band 7, 6, 4 set gives the dust properties deviating from the model at all radii with too broad a constraint range to specify the accurate values of dust temperature, optical depth, and β. Since these features are expected by the synthetic multiband analysis, we confirm that the synthetic multiband analysis is consistent with the results derived from real data.
We report the detection of an excess in dust continuum emission at 233 GHz (1.3 mm in wavelength) in the protoplanetary disk (PPD) around TW Hya revealed through high-sensitivity observations at ∼3 ...au resolution with the Atacama Large Millimeter/submillimeter Array. The sensitivity of the 233 GHz image has been improved by a factor of 3 with regard to that of our previous cycle 3 observations. The overall structure is mostly axisymmetric, and there are apparent gaps at 25 and 41 au as previously reported. The most remarkable new finding is a few astronomical-unit-scale excess emission in the southwest part of the PPD. The excess emission is located at 52 au from the disk center and is 1.5 times brighter than the surrounding PPD at a significance of 12 . We performed a visibility fitting to the extracted emission after subtracting the axisymmetric PPD emission and found that the inferred size and the total flux density of the excess emission are 4.4 × 1.0 au and 250 Jy, respectively. The dust mass of the excess emission corresponds to 0.03 M⊕ if a dust temperature of 18 K is assumed. Because the excess emission can also be marginally identified in the Band 7 image at almost the same position, the feature is unlikely to be a background source. The excess emission can be explained by a dust clump accumulated in a small elongated vortex or a massive circumplanetary disk around a Neptune-mass-forming planet.
ABSTRACT We report the first detection of a gap and a ring in 336 GHz dust continuum emission from the protoplanetary disk around TW Hya, using the Atacama Large Millimeter/Submillimeter Array ...(ALMA). The gap and ring are located at around 25 and 41 au from the central star, respectively, and are associated with the CO snow line at ∼30 au. The gap has a radial width of less than 15 au and a mass deficit of more than 23%, taking into account that the observations are limited to an angular resolution of ∼15 au. In addition, the 13CO and C18O lines show a decrement in CO line emission throughout the disk, down to ∼10 au, indicating a freeze-out of gas-phase CO onto grain surfaces and possible subsequent surface reactions to form larger molecules. The observed gap could be caused by gravitational interaction between the disk gas and a planet with a mass less than super-Neptune (2 ), or could be the result of the destruction of large dust aggregates due to the sintering of CO ice.
Abstract
We report the physical characterization of four CO emitters detected near the bright submillimeter galaxy (SMG) SSA22-AzTEC26. We analyze the data from Atacama Large Millimeter/submillimeter ...Array band 3, 4, and 7 observations of the SSA22-AzTEC26 field. In addition to the targeted SMG, we detect four line emitters with signal-to-noise ratio >5.2 in the cube smoothed with a 300 km s
−1
FWHM Gaussian filter. All four sources have NIR counterparts within 1″. We perform UV-to-FIR spectral energy distribution modeling to derive the photometric redshifts and physical properties. Based on the photometric redshifts, we reveal that two of them are CO(2–1) at redshifts of 1.113 and 1.146 and one is CO(3–2) at
z
= 2.124. The three sources are massive galaxies with a stellar mass ≳10
10.5
M
⊙
, but have different levels of star formation. Two lie within the scatter of the main sequence (MS) of star-forming galaxies at
z
∼ 1–2, and the most massive galaxy lies significantly below the MS. However, all three sources have a gas fraction within the scatter of the MS scaling relation. This shows that a blind CO line search can detect massive galaxies with low specific star formation rates that still host large gas reservoirs and that it also complements targeted surveys, suggesting later gas acquisition and the need for other mechanisms in addition to gas consumption to suppress star formation.
Abstract
We present the results of ALMA observations toward the low-mass Class 0 binary system VLA 1623Aab in the Ophiuchus molecular cloud in
12
CO,
13
CO, and C
18
O(2–1) lines. Our
12
CO (
J
= ...2–1) data reveal that the VLA 1623 outflow consists of twin spatially overlapped outflows/jets. The redshifted northwestern jet exhibits three cycles of wiggle with a spatial period of 1360 ± 10 au, corresponding to a time period of 180 yr. The wiggle-like structure is also found in the position–velocity (PV) diagram, showing an amplitude in the velocity of about 0.9 km s
−1
. Both the period and velocity amplitude of the wiggle are roughly consistent with those expected from the binary parameters, i.e., the orbital period (460 ± 20 yr) and the Keplerian velocity (2.2 km s
−1
). Our
13
CO and C
18
O images show a dense gas nature in the two centimeter/millimeter sources, VLA 1623B and W, and its relation to the outflows, and strongly support the previous interpretation that both are shocked cloudlets. The driving sources of the twin molecular outflows are, therefore, likely to be the VLA 1623Aab binary. The outflow axes of the two molecular outflows are estimated to be inclined by 70° to each other across the plane of sky, implying that protostellar disks are also misaligned by
. Such nature together with a small binary separation of 34 au in one of the youngest protobinary systems seems difficult to explain by disk fragmentation in quiescent environments. Other effects such as turbulence probably play roles.
With an emphasis on improving the fidelity even in super-resolution regimes, new imaging techniques have been intensively developed over the last several years, which may provide substantial ...improvements to the interferometric observation of protoplanetary disks. In this study, sparse modeling (SpM) is applied for the first time to observational data sets taken by the Atacama Large Millimeter/submillimeter Array (ALMA). The two data sets used in this study were taken independently using different array configurations at Band 7 (330 GHz), targeting the protoplanetary disk around HD 142527: one in the shorter-baseline array configuration (∼430 m), and the other in the longer-baseline array configuration (∼1570 m). The image resolutions reconstructed from the two data sets are different by a factor of ∼3. We confirm that the previously known disk structures appear on the images produced by both SpM and CLEAN at the standard beam size. The image reconstructed from the shorter-baseline data using the SpM matches that obtained with the longer-baseline data using the CLEAN, achieving a super-resolution image from which a structure finer than the beam size can be reproduced. Our results demonstrate that ongoing intensive development in the SpM imaging technique is beneficial to imaging with ALMA.
Abstract
We carried out mapping observations toward three nearby molecular clouds, Orion A, Aquila Rift, and M 17, using a new 100 GHz receiver, FOREST, on the Nobeyama 45 m telescope. We describe ...the details of the data obtained such as intensity calibration, data sensitivity, angular resolution, and velocity resolution. Each target contains at least one high-mass star-forming region. The target molecular lines were 12CO (J = 1–0), 13CO (J = 1–0), C18O (J = 1–0), N2H+ (J = 1–0), and CCS (JN = 87–76), with which we covered the density range of 102 cm−3 to 106 cm−3 with an angular resolution of ∼20″ and a velocity resolution of ∼0.1 km s−1. Assuming the representative distances of 414 pc, 436 pc, and 2.1 kpc, the maps of Orion A, Aquila Rift, and M17 cover most of the densest parts with areas of about 7 pc × 15 pc, 7 pc × 7 pc, and 36 pc × 18 pc, respectively. On the basis of the 13CO column density distribution, the total molecular masses are derived to be $3.86 \times 10^{4}\, M_\odot$, $2.67 \times 10^{4}\, M_{\odot }$, and $8.1\times 10^{5}\, M_{\odot }$ for Orion A, Aquila Rift, and M17, respectively. For all the clouds, the H2 column density exceeds the theoretical threshold for high-mass star formation of ≳ 1 g cm−2 only toward the regions which contain current high-mass star-forming sites. For other areas, further mass accretion or dynamical compression would be necessary for future high-mass star formation. This is consistent with the current star formation activity. Using the 12CO data, we demonstrate that our data have enough capability to identify molecular outflows, and for the Aquila Rift we identify four new outflow candidates. The scientific results will be discussed in detail in separate papers.
We present far-infrared (FIR) properties of an extremely luminous infrared galaxy (ELIRG) at zspec = 3.703, WISE J101326.25+611220.1 (WISE 1013+6112). This ELIRG is selected as an IR-bright ...dust-obscured galaxy based on the photometry from the Sloan Digital Sky Survey and the Wide-field Infrared Survey Explorer (WISE). In order to derive its accurate IR luminosity, we perform follow-up observations at 89 and 154 m using the High-resolution Airborne Wideband Camera-plus (HAWC+) on board the 2.7 m Stratospheric Observatory For Infrared Astronomy (SOFIA) telescope. We conduct spectral energy distribution (SED) fitting with CIGALE using 15 photometric data (0.4-1300 m). We successfully pin down FIR SED of WISE 1013+6112 and its IR luminosity is estimated to be LIR = (1.62 0.08) × 1014L☉, making it one of the most luminous IR galaxies in the universe. We determine the dust temperature of WISE 1013+6112 is Tdust = 89 3 K, which is significantly higher than that of other populations such as submillimeter galaxies and FIR-selected galaxies at similar IR luminosities. The resultant dust mass is Mdust = (2.2 0.1) × 108 M☉. This indicates that WISE 1013+6112 has a significant active galactic nucleus and star-forming activity behind a large amount of dust.
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