scholarly journals OH in the Environment of Sgr A

1989 ◽  
Vol 136 ◽  
pp. 421-422
Author(s):  
Aa. Sandqvist ◽  
R. Karlsson ◽  
J. B. Whiteoak
Keyword(s):  
Radial Velocity ◽  
Shell Structure ◽  
Spiral Structure ◽  
Angular Resolution ◽  
Galactic Center ◽  
Absorption Lines ◽  
Molecular Gas ◽  
Center Region ◽  
Circumnuclear Disk ◽  
Sgr A

The 18-cm distribution of OH in the Galactic Center region near Sgr A has been mapped in all four of the 1612, 1665, 1667 and 1720 MHz OH absorption lines using the VLA with 4 arcsec angular resolution and 9 kms-1 velocity resolution. The OH gas at +50 and +20 kms-l is seen clearly in absorption against the shell structure of Sgr A East but not against the spiral structure of Sgr A West, possibly implying that this molecular gas lies between the two continuum components - behind Sgr A West and in front of Sgr A East. Inside the Circumnuclear Disk, there is a new neutral streamer which sweeps from the disk in towards Sgr A∗ as the observed radial velocity decreases from +78 to +16 kms-1. The streamer may have a negative-velocity counterpart on the opposite side of Sgr A∗.

scholarly journals FIR Spectroscopy of the Galactic Center: Hot and Warm Molecular Gas

2016 ◽  
Vol 11 (S322) ◽  
pp. 168-169
Author(s):  
Javier R. Goicoechea ◽  
Mireya Etxaluze ◽  
José Cernicharo ◽  
Maryvonne Gerin ◽  
Jerome Pety ◽  
...  
Keyword(s):  
Angular Resolution ◽  
Galactic Center ◽  
Rotational Line ◽  
Molecular Gas ◽  
Central Cavity ◽  
Stellar Cluster ◽  
Line Intensities ◽  
The Galaxy ◽  
Circumnuclear Disk ◽  
Sgr A

AbstractThe angular resolution (~10″) achieved by the Herschel Space Observatory ~3.5 m telescope at FIR wavelengths allowed us to roughly separate the emission toward the inner parsec of the galaxy (the central cavity) from that of the surrounding circumnuclear disk (the CND). The FIR spectrum toward Sgr A* is dominated by intense [O iii], [O i], [C ii], [N iii], [N ii], and [C i] fine-structure lines (in decreasing order of luminosity) arising in gas irradiated by the strong UV field from the central stellar cluster. The high-J CO rotational line intensities observed at the interface between the inner CND and the central cavity are consistent with a hot isothermal component at Tk ≈ 103.1 K and n(H2)≈ 104 cm−3. They are also consistent with a distribution of lower temperatures at higher gas density, with most CO at Tk≈300 K. The hot CO component (either the bulk of the CO column density or just a small fraction depending on the above scenario) likely results from a combination of UV and shock-driven heating. If UV-irradiated and heated dense clumps do not exist, shocks likely dominate the heating of the hot molecular gas component. Although this component is beam diluted in our FIR observations, it may be resolved at much higher angular resolution. An ALMA project using different molecular tracers to characterize UV-irradiated shocks in the innermost layers of the CND is ongoing.

scholarly journals Detailed distributions of the CO J = (2 − 1)/J = (1 − 0) intensity ratios toward a large area of the central molecular zone

2013 ◽  
Vol 9 (S303) ◽  
pp. 106-108
Author(s):  
Kazufumi Torii ◽  
Rei Enokiya ◽  
Yasuo Fukui ◽  
Hiroaki Yamamoto ◽  
Akiko Kawamura ◽  
...  
Keyword(s):  
Angular Resolution ◽  
Galactic Center ◽  
Galactic Plane ◽  
Area Coverage ◽  
High Angular Resolution ◽  
Molecular Gas ◽  
Large Area ◽  
First Results ◽  
Intensity Ratios ◽  
Sgr A

AbstractWe present the first results of the new CO J = (2 − 1) observations toward the central molecular zone (CMZ) using the NANTEN2 telescope at an angular resolution of 100″. Large area coverage of 4° × 2° in l and b and a high angular resolution of 100″ enable us to investigate detailed structures of the molecular gas in the CMZ including peculiar molecular filaments perpendicularly to the Galactic plane to b > |0.5°|. The major components of the CMZ, e.g., Sgr A, Sgr B and Sgr C cloud complexes, show high CO J = (2 − 1)/J = (1 − 0) ratios around 0.9, indicating highly excited conditions of the molecular gas, while the local foreground components show less than 0.4. The molecular filaments show the typical ratios of 0.6–0.7 indicate that they are indeed located in the Galactic center.

scholarly journals Molecular gas in the immediate vicinity of Sgr A* seen with ALMA

2016 ◽  
Vol 11 (S322) ◽  
pp. 129-132
Author(s):  
Lydia Moser ◽  
Álvaro Sánchez-Monge ◽  
Andreas Eckart ◽  
Miguel A. Requena-Torres ◽  
Macarena García-Marin ◽  
...  
Keyword(s):  
Galactic Center ◽  
Line Emission ◽  
Molecular Gas ◽  
Future Studies ◽  
X Ray ◽  
Circumnuclear Disk ◽  
Sgr A ◽  
Central Parsec ◽  
Cloud Cores ◽  
Cold Core

AbstractWe report serendipitous detections of line emission with ALMA in band 3, 6, and 7 in the central parsec of the Galactic center at an up to now highest resolution (<0.7″). Among the highlights are the very first and highly resolved images of sub-mm molecular emission of CS, H13CO+, HC3N, SiO, SO, C2H, and CH3OH in the immediate vicinity (~1″ in projection) of Sgr A* and in the circumnuclear disk (CND). The central association (CA) of molecular clouds shows three times higher CS/X (X: any other observed molecule) luminosity ratios than the CND suggesting a combination of higher excitation - by a temperature gradient and/or IR-pumping - and abundance enhancement due to UV- and/or X-ray emission. We conclude that the CA is closer to the center than the CND is and could be an infalling clump consisting of denser cloud cores embedded in diffuse gas. Moreover, we identified further regions in and outside the CND that are ideally suited for future studies in the scope of hot/cold core and extreme PDR/XDR chemistry and consequent star formation in the central few parsecs.

scholarly journals NH3 Observations of the Sgr A Complex Region with the Nobeyama Millimeter Array

1989 ◽  
Vol 136 ◽  
pp. 371-377 ◽  
Author(s):  
S. K. Okumura ◽  
M. Ishiguro ◽  
E. B. Fomalont ◽  
Y. Chikada ◽  
T. Kasuga ◽  
...  
Keyword(s):  
Strong Interaction ◽  
Molecular Clouds ◽  
Galactic Center ◽  
Molecular Gas ◽  
Kinetic Temperature ◽  
Complex Region ◽  
Physical Conditions ◽  
Center Region ◽  
Sgr A ◽  
The Continuum

We report NH3 observations of the Sgr A complex region including Sgr A West and the 20 km/s and 50 km/s molecular clouds (M–0.13–0.08 and M–0.02–0.07) using the Nobeyama Millimeter Array and the 45m telescope. NH3(1,1) and (2,2) lines were simultaneously observed to estimate the kinetic temperature. Our results suggest strong interaction between the molecular clouds and the continuum sources in the Sgr A complex. The interaction with continuum sources might be an important factor in determining the physical conditions of molecular gas in the galactic center region.

scholarly journals Mini-Spiral at the Galactic Center: A Link between its Structure and the Value of a Central Point Mass

1996 ◽  
Vol 169 ◽  
pp. 241-246
Author(s):  
A.M. Fridman ◽  
O.V. Khoruzhii ◽  
V.V. Lyakhovich ◽  
L. Ozernoy ◽  
L. Blitz
Keyword(s):  
Galactic Center ◽  
Density Wave ◽  
Neutral Hydrogen ◽  
Wave Model ◽  
Molecular Gas ◽  
Stellar Cluster ◽  
Nonthermal Radio ◽  
H Ii Region ◽  
Circumnuclear Disk ◽  
Sgr A

The innermost 2 pc contain a rotating ring (“circumnuclear disk”) of molecular gas, neutral hydrogen, and dust with an embedded H II region called Sgr A West; a dense stellar cluster; and a compact nonthermal radio source Sgr A∗ (for a recent review, see Blitz et al. 1993). The clumped, spiral-shaped morphology of Sgr A West, sometimes called lthe mini-spiral”, has been a subject of numerous speculations concerning its origin (for a review, see Genzel & Townes 1987). Lacy et al. (1991) demonstrated that both the kinematics and shape of a part of Sgr A West can be fairly well approximated using an one-armed density-wave model.

scholarly journals The geometry of the magnetic field in the central molecular zone measured by PILOT

2019 ◽  
Vol 630 ◽  
pp. A74 ◽  
Author(s):  
A. Mangilli ◽  
J. Aumont ◽  
J.-Ph. Bernard ◽  
A. Buzzelli ◽  
G. de Gasperis ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Molecular Clouds ◽  
Angular Resolution ◽  
Galactic Center ◽  
Galactic Plane ◽  
Mean Field ◽  
Field Orientation ◽  
Center Region ◽  
The Mean ◽  
The Magnetic Field

We present the first far infrared (FIR) dust emission polarization map covering the full extent of Milky Way’s central molecular zone (CMZ). The data, obtained with the PILOT balloon-borne experiment, covers the Galactic center region − 2° < ℓ < 2°, − 4° < b < 3° at a wavelength of 240 μm and an angular resolution of 2.2′. From our measured dust polarization angles, we infer a magnetic field orientation projected onto the plane of the sky (POS) that is remarkably ordered over the full extent of the CMZ, with an average tilt angle of ≃22° clockwise with respect to the Galactic plane. Our results confirm previous claims that the field traced by dust polarized emission is oriented nearly orthogonally to the field traced by GHz radio synchrotron emission in the Galactic center region. The observed field structure is globally compatible with the latest Planck polarization data at 353 and 217 GHz. Upon subtraction of the extended emission in our data, the mean field orientation that we obtain shows good agreement with the mean field orientation measured at higher angular resolution by the JCMT within the 20 and 50 km s−1 molecular clouds. We find no evidence that the magnetic field orientation is related to the 100 pc twisted ring structure within the CMZ. The low polarization fraction in the Galactic center region measured with Planck at 353 GHz combined with a highly ordered projected field orientation is unusual. This feature actually extends to the whole inner Galactic plane. We propose that it could be caused by the increased number of turbulent cells for the long lines of sight towards the inner Galactic plane or to dust properties specific to the inner regions of the Galaxy. Assuming equipartition between magnetic pressure and ram pressure, we obtain magnetic field strength estimates of the order of 1 mG for several CMZ molecular clouds.

scholarly journals Kinematic study of the molecular gas associated with two cometary globules in Sh2−236

2020 ◽  
Vol 633 ◽  
pp. A27
Author(s):  
M. E. Ortega ◽  
S. Paron ◽  
M. B. Areal ◽  
M. Rubio
Keyword(s):  
Star Formation ◽  
Radial Velocity ◽  
Angular Resolution ◽  
Optical Data ◽  
Molecular Gas ◽  
Diffuse Emission ◽  
B Stars ◽  
Kinematic Study ◽  
Star Formation Activity ◽  
Ubiquitous Presence

Aims. Cometary globules, dense molecular gas structures exposed to UV radiation, are found inside H II regions. Understanding the nature and origin of these structures through a kinematic study of the molecular gas could be useful to advance in our knowledge of the interplay between radiation and molecular gas. Methods. Using the Atacama Submillimeter Telescope Experiment (Chile), we carried out molecular observations toward two cometary globules (Sim129 and Sim130) in the H II region Sh2−236. We mapped two regions of about 1′ × 1′ with the 12CO J = 3−2 and HCO+ J = 4−3 lines. Additionally, we carried out two single pointings with the C2H N = 4–3, HNC, and HCN J = 4−3 transitions. The angular resolution was about 22′′. We combined our molecular observations with public infrared and optical data to analyze the distribution and kinematics of the molecular gas. Results. We find kinematic signatures of infalling gas in the 12CO J = 3−2 and C2H N = 4−3 spectra toward Sim 129. We detect HCO+, HCN, and HNC J = 4−3 only toward Sim 130. The HCN/HNC integrated ratio of about three found in Sim 130 suggests that the possible star-formation activity inside this globule has not yet ionized the gas. The location of the NVSS source 052255+33315, which peaks toward the brightest border of the globule, supports this scenario. The non-detection of these molecules toward Sim 129 could be due to the radiation field arising from the star-formation activity inside this globule. The ubiquitous presence of the C2H molecule toward Sim 129 and Sim 130 evidences the action of the nearby O-B stars irradiating the external layer of both globules. Based on the mid-infrared 5.8 μm emission, we identify two new structures: (1) a region of diffuse emission (R1) located, in projection, in front of the head of Sim 129 and (2) a pillar-like feature (P1) placed besides Sim 130. Based on the 12CO J = 3−2 transition, we find molecular gas associated with Sim 129, Sim 130, R1, and P1 at radial velocities of −1.5, −11, +10, and +4 km s−1, respectively. Therefore, while Sim 129 and P1 are located at the far side of the shell, Sim 130 is placed at the near side, consistent with earlier results. Finally, the molecular gas related to R1 exhibits a radial velocity that differs in more than 11 km s−1 with the radial velocity of S129, which suggests that while S129 is located at the far side of the expanding shell, R1 would be placed well beyond.

scholarly journals A Survey of Radio Recombination Line Emission From the Galactic Center Region

1989 ◽  
Vol 136 ◽  
pp. 159-166 ◽  
Author(s):  
K. R. Anantharamaiah ◽  
Farhad Yusef-Zadeh
Keyword(s):  
Galactic Center ◽  
Line Emission ◽  
Radio Continuum ◽  
Strong Line ◽  
Line Profiles ◽  
Ionized Gas ◽  
Center Region ◽  
Radio Recombination Line ◽  
Nonthermal Emission ◽  
Sgr A

Preliminary results of a systematic survey of H78α, H91α and H98β emission from the inner 40′ of the Galactic center region are presented. This region consists of two prominent continuum features, the Sgr A complex and the radio continuum Arc. In spite of much nonthermal emission arising from these two features, we detected strong line emission with large line widths in more than half of the observed 130 positions. Many of the detections are new, in particular −50 km s−1 ionized gas linking the Sgr A complex and the Arc, β line emission from GO.1+0.08 (the arched filaments), and α line emission from the loop-like structures which surround the non-thermal filaments near G0.2−0.05. We find that much of the detected lines are probably associated with the −50 km s−1 and the 20 km s−1 molecular clouds, known to lie near the Galactic center. We present line profiles of a number of Galactic center sources including Sgr B1, Sgr C and Sgr D.

scholarly journals Molecular Gas Feeding the Circumnuclear Disk of the Galactic Center

2017 ◽  
Vol 847 (1) ◽  
pp. 3 ◽  
Author(s):  
Pei-Ying Hsieh ◽  
Patrick M. Koch ◽  
Paul T. P. Ho ◽  
Woong-Tae Kim ◽  
Ya-Wen Tang ◽  
...  
Keyword(s):  
Galactic Center ◽  
Molecular Gas ◽  
Circumnuclear Disk

scholarly journals Geodesic motion of S2 and G2 as a test of the fermionic dark matter nature of our Galactic core

2020 ◽  
Vol 641 ◽  
pp. A34 ◽  
Author(s):  
E. A. Becerra-Vergara ◽  
C. R. Argüelles ◽  
A. Krut ◽  
J. A. Rueda ◽  
R. Ruffini
Keyword(s):  
Dark Matter ◽  
Radial Velocity ◽  
Drag Force ◽  
Gravitational Potential ◽  
Galactic Center ◽  
Critical Mass ◽  
Time Dependent ◽  
Fermion Mass ◽  
Massive Black Hole ◽  
Sgr A

The motion of S-stars around the Galactic center implies that the central gravitational potential is dominated by a compact source, Sagittarius A* (Sgr A*), which has a mass of about 4 × 106 M⊙ and is traditionally assumed to be a massive black hole (BH). The explanation of the multiyear accurate astrometric data of the S2 star around Sgr A*, including the relativistic redshift that has recently been verified, is particularly important for this hypothesis and for any alternative model. Another relevant object is G2, whose most recent observational data challenge the scenario of a massive BH: its post-pericenter radial velocity is lower than expected from a Keplerian orbit around the putative massive BH. This scenario has traditionally been reconciled by introducing a drag force on G2 by an accretion flow. As an alternative to the central BH scenario, we here demonstrate that the observed motion of both S2 and G2 is explained in terms of the dense core – diluted halo fermionic dark matter (DM) profile, obtained from the fully relativistic Ruffini-Argüelles-Rueda (RAR) model. It has previously been shown that for fermion masses 48−345 keV, the RAR-DM profile accurately fits the rotation curves of the Milky Way halo. We here show that the solely gravitational potential of such a DM profile for a fermion mass of 56 keV explains (1) all the available time-dependent data of the position (orbit) and line-of-sight radial velocity (redshift function z) of S2, (2) the combination of the special and general relativistic redshift measured for S2, (3) the currently available data on the orbit and z of G2, and (4) its post-pericenter passage deceleration without introducing a drag force. For both objects, we find that the RAR model fits the data better than the BH scenario: the mean of reduced chi-squares of the time-dependent orbit and z data are ⟨χ̄2⟩S2,RAR ≈ 3.1 and ⟨χ̄2⟩S2,BH ≈ 3.3 for S2 and ⟨χ̄2⟩G2,RAR ≈ 20 and ⟨χ̄2⟩G2,BH ≈ 41 for G2. The fit of the corresponding z data shows that while for S2 we find comparable fits, that is, χ̄2z,RAR ≈ 1.28 and χ̄2z,BH ≈ 1.04, for G2 the RAR model alone can produce an excellent fit of the data, that is, χ̄2z,RAR ≈ 1.0 and χ̄2z,BH ≈ 26. In addition, the critical mass for gravitational collapse of a degenerate 56 keV-fermion DM core into a BH is ∼ 108 M⊙. This result may provide the initial seed for the formation of the observed central supermassive BH in active galaxies, such as M 87.

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