We report the results of high-resolution molecular line observations of the high-velocity compact cloud HCN-0.085-0.094 with the Atacama Large Millimeter/submillimeter Array. The HCN J = 4-3, HCO+ J ...= 4-3, and CS J = 7-6 line images reveal that HCN-0.085-0.094 consists mainly of three small clumps with extremely broad velocity widths. Each of the three clumps has a 5.5 GHz radio continuum counterpart in its periphery toward Sgr A*. The positional relationship indicates that their surfaces have been ionized by ultraviolet photons from young stars in the central cluster, suggesting the clumps are in close proximity to the Galactic nucleus. One of the three clumps has a ring-like structure with a very steep velocity gradient. This kinematical structure suggests an orbit around a point-like object with a mass of ∼104 M . The absence of stellar counterparts indicates that the point-like object may be a quiescent black hole. This discovery adds another intermediate-mass black hole candidate in the central region of our Galaxy.
We report the discovery of molecular gas streams orbiting around an invisible massive object in the central region of our Galaxy, based on the high-resolution molecular line observations with the ...Atacama Large Millimeter/submillimeter Array. The morphology and kinematics of these streams can be reproduced well through two Keplerian orbits around a single point mass of (3.2 0.6) × 104 M . We also found ionized gas toward the inner part of the orbiting gas, indicating dissociative shock and/or photoionization. Our results provide new circumstantial evidences for a wandering intermediate-mass black hole in the Galactic center, suggesting also that high-velocity compact clouds can be probes of quiescent black holes that abound in our Galaxy.
ABSTRACT We mapped the high-velocity compact cloud CO-0.40-0.22 in 21 molecular lines in the 3 mm band using the Nobeyama Radio Observatory 45 m radio telescope. Eighteen lines were detected from ...CO-0.40-0.22. The map of each detected line shows that this cloud has a compact appearance (d 3 pc) and extremely broad velocity width (ΔV 100 km s−1). The mass and kinetic energy of CO-0.40-0.22 are estimated to be 103.6 M and 1049.7 erg, respectively. The representative position-velocity map along the major axis shows that CO-0.40-0.22 consists of an intense region with a shallow velocity gradient and a less intense high-velocity wing. Here, we show that this kinematical structure can be attributed to a gravitational kick to the molecular cloud caused by an invisible compact object with a mass of ∼105 M . Its compactness and the absence of counterparts at other wavelengths suggest that this massive object is an intermediate-mass black hole.
Abstract We report the results of the CO J = 1–0 and SiO J = 2–1 mapping observations toward the broad-velocity-width molecular feature (BVF) CO 16.134–0.553 with the Nobeyama Radio Observatory 45 m ...telescope. The high-quality CO map shows that the 5 pc size BVF bridges two separate velocity components at V LSR ≃ 40 km s −1 and 65 km s −1 in the position–velocity space. The kinetic power of CO 16.134–0.553 amounts to 7.8 × 10 2 L ⊙ , whereas no apparent driving sources were identified. Prominent SiO emission was detected from the BVF and its root in the V LSR ≃ 40 km s −1 component. In the CO Galactic plane survey data, CO 16.134–0.553 appears to correspond to the Galactic eastern rim of a 15 pc diameter expanding CO shell. A 1° diameter H i emission void and 4° long vertical H i filament were also found above and below the CO shell, respectively. We propose that the high-velocity plunge of a dark matter subhalo with a clump of baryonic matter was responsible for the formation of the H i void, CO 16.134–0.553/CO shell, and the H i filament.
Abstract
We report the results of observations toward the center of the molecular cloud CO 0.02–0.02 made using the Atacama Large Millimeter/Submillimeter Array. The successfully obtained 1″ ...resolution images of CO
J
= 3–2, H
13
CN
J
= 4–3, H
13
CO
+
J
= 4–3, SiO
J
= 8–7, CH
3
OH
J
K
a
,
K
c
= 7
1,7
–6
1,6
A
+
lines, and 900
μ
m continuum show several new features, which have not been identified in previous observations. The dense gas probe (H
13
CN, SiO, CH
3
OH) images are dominated by a pair of northeast-southwest elongated filaments, which may be the main body of CO 0.02–0.02. Two striped patterns perpendicular to each other (F1 and F2) and a high-velocity feature (HV), which appear in different velocity ranges, were prominent in the CO image. An emission hole that may represent an expanding feature was found in the F1 velocity range. F2 appeared to align along the western edge of a 20 pc × 13 pc ellipse (the Large Shell) identified in the single-dish CO map. The HV contains eight compact clumps at the positive high-velocity end of the CO emissions. Based on these results, we propose a formation scenario for CO 0.02–0.02; internal explosions of supernovae, external perturbations by the Large Shell, and gravitational acceleration by a less-luminous star cluster have formed CO 0.02–0.02 in its current state.
Abstract
In this paper, we report the discovery of an isolated, peculiar compact cloud with a steep velocity gradient at 2.′6 northwest of Sgr A*. This “Tadpole” molecular cloud is unique owing to ...its characteristic head-tail structure in the position–velocity space. By tracing the CO
J
= 3–2 intensity peak in each velocity channel, we noticed that the kinematics of the Tadpole can be well reproduced by a Keplerian motion around a point-like object with a mass of 1 × 10
5
M
⊙
. Changes in line intensity ratios along the orbit are consistent with the Keplerian orbit model. The spatial compactness of the Tadpole and absence of bright counterparts in other wavelengths indicate that the object could be an intermediate-mass black hole.
Abstract
We performed a systematic search for broad-velocity-width molecular features (BVFs) in the disk part of our Galaxy by using the CO
J
= 1–0 survey data obtained with the Nobeyama Radio ...Observatory 45 m telescope. From this search, 58 BVFs were identified. In comparisons with the infrared and radio continuum images, 36 BVFs appeared to have both infrared and radio continuum counterparts, and 15 of them are described as molecular outflows from young stellar objects in the literature. In addition, 21 BVFs have infrared counterparts only, and eight of them are described as molecular outflows in the literature. One BVF (CO 16.134–0.553) does not have any luminous counterpart in the other wavelengths, which suggests that it may be an analog of high-velocity compact clouds in the Galactic center.
We discovered two small high-velocity compact clouds (HVCCs) in the HCN J = 4-3 and J = 3-2 maps of the central 20 pc of our Galaxy. Both HVCCs have broad velocity widths ( km s−1) and compact sizes ...( ), and originate from the dense molecular clouds in the position-velocity space. One of them has a faint counterpart in a Paschen- image. Their spatial structure, kinematics, and absence of luminous stellar object are compatible with the notion that each of the small HVCCs is driven by the plunge of an invisible compact object into a molecular cloud. Such objects are most likely inactive, isolated black holes.
Abstract
We performed Nyquist-sampled mapping observations of the central molecular zone of our Galaxy in the J = 1–0 lines of CO, 13CO, and C18O using the 45 m telescope at the Nobeyama Radio ...Observatory. The newly obtained data sets were an improvement by a factor of four in spatial resolution of the CO data previously obtained with the same telescope 22 years ago, providing the highest angular resolution CO atlas of this special area of the Galaxy. The data cover the area: −0${^{\circ}_{.}}$8 ≤ l ≤ +1${^{\circ}_{.}}$4 and −0${^{\circ}_{.}}$35 ≤ b ≤ +0${^{\circ}_{.}}$35 with a 15″ beamwidth. Total intensity ratios for CO J = 3–2/J = 1–0, 13CO/CO J = 1–0 and C18O/13CO J = 1–0, are 0.70 ± 0.06, 0.12 ± 0.01, and 0.14 ± 0.01, respectively. The high-resolution CO images show the fine structure of the molecular gas and enable us to identify a number of compact clouds with broad velocity widths, i.e., high-velocity compact clouds. We conducted a detailed comparison of our CO J = 1–0 data with the CO J = 3–2 data obtained with the James Clerk Maxwell Telescope to derive the distribution and kinematics of the highly excited gas. Three, out of four, of the previously identified high CO J = 3–2/J = 1–0 ratio areas at l = +1${^{\circ}_{.}}$3, 0${^{\circ}_{.}}$0, and −0${^{\circ}_{.}}$4 were confirmed with a higher spatial resolution. In addition to these, we identified several very compact, high CO J = 3–2/J = 1–0 spots with broad velocity widths for the first time. These are candidates for accelerated gas in the vicinity of invisible, point-like massive objects.
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