scholarly journals G−0.02−0.07, the compact H ii region complex nearest to the galactic center with ALMA

2019 ◽  
Vol 71 (6) ◽  
Author(s):  
Masato Tsuboi ◽  
Yoshimi Kitamura ◽  
Kenta Uehara ◽  
Atsushi Miyazaki ◽  
Ryosuke Miyawaki ◽  
...  
Keyword(s):  
Shock Wave ◽  
Galactic Center ◽  
Emission Lines ◽  
Continuum Emission ◽  
Molecular Gas ◽  
H Ii Regions ◽  
Recombination Line ◽  
The Galaxy ◽  
H Ii Region ◽  
Absorption Features

Abstract We have observed the compact H ii region complex nearest to the dynamical center of the Galaxy, G−0.02−0.07, using ALMA in the H42α recombination line, CS J = 2–1, H13CO+J = 1–0, and SiO v = 0, J = 2–1 emission lines, and the 86 GHz continuum emission. The H ii regions HII-A to HII-C in the cluster are clearly resolved into a shell-like feature with a bright half and a dark half in the recombination line and continuum emission. The analysis of the absorption features in the molecular emission lines show that H ii-A, B, and C are located on the near side of the “Galactic center 50 km s−1 molecular cloud” (50MC), but HII-D is located on the far side of it. The electron temperatures and densities ranges are Te = 5150–5920 K and ne = 950–2340 cm−3, respectively. The electron temperatures in the bright half are slightly lower than those in the dark half, while the electron densities in the bright half are slightly higher than those in the dark half. The H ii regions are embedded in the ambient molecular gas. There are some molecular gas components compressed by a C-type shock wave around the H ii regions. From the line width of the H42α recombination line, the expansion velocities of HII-A, HII-B, HII-C, and HII-D are estimated to be Vexp = 16.7, 11.6, 11.1, and 12.1 km s−1, respectively. The expansion timescales of HII-A, HII-B, HII-C, and HII-D are estimated to be tage ≃ 1.4 × 104, 1.7 × 104, 2.0 × 104, and 0.7 × 104 yr, respectively. The spectral types of the central stars from HII-A to HII-D are estimated to be O8V, O9.5V, O9V, and B0V, respectively. These derived spectral types are roughly consistent with the previous radio estimation. The positional relation among the H ii regions, the SiO molecule enhancement area, and Class-I maser spots suggest that a shock wave caused by a cloud–cloud collision propagated along the line from HII-C to HII-A in the 50MC. The shock wave would have triggered the massive star formation.

scholarly journals IRTF/TEXES observations of the H ii regions H1 and H2 in the Galactic Centre

2017 ◽  
Vol 470 (1) ◽  
pp. 561-575 ◽  
Author(s):  
Hui Dong ◽  
John H. Lacy ◽  
Rainer Schödel ◽  
Francisco Nogueras-Lara ◽  
Teresa Gallego-Calvente ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Galactic Center ◽  
Galactic Centre ◽  
H Ii Regions ◽  
Stellar Cluster ◽  
The Galaxy ◽  
H Ii Region ◽  
Sgr A ◽  
Projected Distance

Abstract We present new [Ne ii] (12.8 μm) IRTF/TEXES observations of the Galactic Center H ii regions H1 and H2, which are at a projected distance of ∼11 pc from the centre of the Galaxy. The new observations allow us to map the radial velocity distributions of ionized gas. The high spectroscopic resolution (∼4 km s−1) helps us to disentangle different velocity components and enables us to resolve previous ambiguity regarding the nature of these sources. The spatial distributions of the intensity and radial velocity of the [Ne ii] line are mapped. In H1, the intensity distributions of the Paschen-α (1.87 μm) and [Ne ii] lines are significantly different, which suggests a strong variation of extinction across the H ii region of AK ∼ 0.56. The radial velocity distributions across these H ii regions are consistent with the predictions of a bow-shock model for H1 and the pressure-driven model for H2. Furthermore, we find a concentration of bright stars in H2. These stars have similar H − Ks colours and can be explained as part of a 2-Myr-old stellar cluster. H2 also falls on the orbit of the molecular clouds, suggested to be around Sgr A*. Our new results confirm what we had previously suggested: The O supergiant P114 in H1 is a runaway star, moving towards us through the −30 to 0 km s−1 molecular cloud, whereas the O If star P35 in H2 formed in situ, and may mark the position of a so-far unknown small star cluster formed within the central 30 pc of the Galaxy.

scholarly journals Hidden molecular outflow in the LIRG Zw 049.057

2018 ◽  
Vol 609 ◽  
pp. A75 ◽  
Author(s):  
N. Falstad ◽  
S. Aalto ◽  
J. G. Mangum ◽  
F. Costagliola ◽  
J. S. Gallagher ◽  
...  
Keyword(s):  
Far Infrared ◽  
Minor Axis ◽  
Spectral Lines ◽  
Continuum Emission ◽  
High Angular Resolution ◽  
Molecular Gas ◽  
Nuclear Activity ◽  
Molecular Outflow ◽  
The Galaxy ◽  
Excitation Conditions

Context. Feedback in the form of mass outflows driven by star formation or active galactic nuclei is a key component of galaxy evolution. The luminous infrared galaxy Zw 049.057 harbours a compact obscured nucleus with a possible far-infrared signature of outflowing molecular gas. Due to the high optical depths at far-infrared wavelengths, however, the interpretation of the outflow signature is uncertain. At millimeter and radio wavelengths, the radiation is better able to penetrate the large columns of gas and dust responsible for the obscuration. Aims. We aim to investigate the molecular gas distribution and kinematics in the nucleus of Zw 049.057 in order to confirm and locate the molecular outflow, with the ultimate goal to understand how the nuclear activity affects the host galaxy. Methods. We used high angular resolution observations from the Submillimeter Array (SMA), the Atacama Large Millimeter/submillimeter Array (ALMA), and the Karl G. Jansky Very Large Array (VLA) to image the CO J = 2–1 and J = 6–5 emission, the 690 GHz continuum, the radio centimeter continuum, and absorptions by rotationally excited OH. Results. The CO line profiles exhibit wings extending ~ 300 km s-1 beyond the systemic velocity. At centimeter wavelengths, we find a compact (~ 40 pc) continuum component in the nucleus, with weaker emission extending several 100 pc approximately along the major and minor axes of the galaxy. In the OH absorption lines toward the compact continuum, wings extending to a similar velocity as for the CO are only seen on the blue side of the profile. The weak centimeter continuum emission along the minor axis is aligned with a highly collimated, jet-like dust feature previously seen in near-infrared images of the galaxy. Comparison of the apparent optical depths in the OH lines indicate that the excitation conditions in Zw 049.057 differ from those within other OH megamaser galaxies. Conclusions. We interpret the wings in the spectral lines as signatures of a nuclear molecular outflow. A relation between this outflow and the minor axis radio feature is possible, although further studies are required to investigate this possible association and understand the connection between the outflow and the nuclear activity. Finally, we suggest that the differing OH excitation conditions are further evidence that Zw 049.057 is in a transition phase between megamaser and kilomaser activity.

scholarly journals Ultraviolet emission line imaging of planetary nebulae with GALEX

2011 ◽  
Vol 7 (S283) ◽  
pp. 308-309 ◽  
Author(s):  
Luciana Bianchi ◽  
Arturo Manchado ◽  
Karl Forster
Keyword(s):  
Galaxy Evolution ◽  
Broad Band ◽  
Planetary Nebulae ◽  
Emission Lines ◽  
Continuum Emission ◽  
Ultraviolet Emission ◽  
The Galaxy ◽  
Optical Domain ◽  
Line Imaging ◽  
Shock Fronts

AbstractGALEX (the Galaxy Evolution Explorer) has provided far-UV(1344-1786Å) and near-UV(1771-2831Å) imaging of several Planetary Nebulae (e.g., Bianchi et al. 2008, Bianchi 2012), with flux limits ~27.5 mag/sq.arcsec for objects in the Medium-deph Imaging Survey (MIS). PNe images in the GALEX broad-band UV filters include flux from both nebular line and continuum emission. We use the GALEX grism observing mode to obtain slitless spectral imaging of a sample of PNe with diameters >1′, in the near-UV. We show the first data from this program. The grism produces 2D images of the prominent UV nebular emission lines, when such lines dominate the flux. Combined with monochromatic images of diagnostic lines in the optical domain, such data help detect and interpret ionization and shock fronts, especially in faint nebular regions.

scholarly journals Radio Continuum Emission from the Nuclei of Normal Galaxies

1980 ◽  
Vol 5 ◽  
pp. 177-184 ◽  
Author(s):  
J. M. van der Hulst
Keyword(s):  
Radio Emission ◽  
Galactic Center ◽  
Galactic Nuclei ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Thermal Source ◽  
Very Large Array ◽  
Normal Galaxies ◽  
The Galaxy ◽  
Sgr A

During the last few years detailed and sensitive observations of the radio emission from the nuclei of many normal spiral galaxies has become available. Observations from the Very Large Array (VLA) of the National Radio Astronomy Observatory (NRAO1), in particular, enable us to distinguish details on a scale of ≤100 pc for galaxies at distances less than 21 Mpc. The best studied nucleus, however, still is the center of our own Galaxy (see Oort 1977 and references therein). Its radio structure is complex. It consists of an extended non-thermal component 200 × 70 pc in size, with embedded therein several giant HII regions and the central source Sgr A (˜9 pc in size). Sgr A itself consists of a thermal source, Sgr A West, located at the center of the Galaxy, and a weaker, non-thermal source, Sgr A East. Sgr A West moreover contains a weak, extremely compact (≤10 AU) source. The radio morphology of several other galactic nuclei is quite similar to that of the Galactic Center, as will be discussed in section 2. Recent reviews of the radio properties of the nuclei of normal galaxies have been given by Ekers (1978a,b) and De Bruyn (1978). The latter author, however, concentrates on galaxies with either active nuclei or an unusual radio morphology. In this paper I will describe recent results from the Westerbork Synthesis Radio Telescope (WSRT, Hummel 1979), the NRAO 3-element interferometer (Carlson, 1977; Condon and Dressel 1978), and the VLA (Heckman et al., 1979; Van der Hulst et al., 1979). I will discuss the nuclear radio morphology in section 2, the luminosities in section 3, and the spectra in section 4. In section 5 I will briefly comment upon the possible implications for the physical processes in the nuclei that are responsible for the radio emission.

scholarly journals Rotating ionized gas ring around the Galactic center IRS13E3

2019 ◽  
Vol 71 (5) ◽  
Author(s):  
Masato Tsuboi ◽  
Yoshimi Kitamura ◽  
Takahiro Tsutsumi ◽  
Ryosuke Miyawaki ◽  
Makoto Miyoshi ◽  
...  
Keyword(s):  
Galactic Center ◽  
Mass Density ◽  
Angular Size ◽  
High Mass ◽  
Continuum Emission ◽  
Supporting Evidence ◽  
Recombination Line ◽  
Ionized Gas ◽  
Sgr A ◽  
The Continuum

Abstract We detected a compact ionized gas associated physically with IRS13E3, an intermediate mass black hole (IMBH) candidate in the Galactic center, in the continuum emission at 232 GHz and H30α recombination line using ALMA Cy.5 observation (2017.1.00503.S, P.I. M.Tsuboi). The continuum emission image shows that IRS13E3 is surrounded by an oval-like structure. The angular size is 0${^{\prime\prime}_{.}}$093 ± 0${^{\prime\prime}_{.}}$006 × 0${^{\prime\prime}_{.}}$061 ± 0${^{\prime\prime}_{.}}$004 (1.14 × 1016 cm × 0.74 × 1016 cm). The structure is also identified in the H30α recombination line. This is seen as an inclined linear feature in the position–velocity diagram, which is usually a defining characteristic of a rotating gas ring around a large mass. The gas ring has a rotating velocity of Vrot ≃ 230 km s−1 and an orbit radius of r ≃ 6 × 1015 cm. From these orbit parameters, the enclosed mass is estimated to be $M_{\mathrm{IMBH}}\simeq 2.4\times 10^{4}\, M_{\odot }$. The mass is within the astrometric upper limit mass of the object adjacent to Sgr A*. Considering IRS13E3 has an X-ray counterpart, the large enclosed mass would be supporting evidence that IRS13E3 is an IMBH. Even if a dense cluster corresponds to IRS13E3, the cluster would collapse into an IMBH within τ < 107 yr due to the very high mass density of $\rho \gtrsim 8\times 10^{11}\, M_{\odot }\:$pc−3. Because the orbital period is estimated to be as short as T = 2πr/Vrot ∼ 50–100 yr, the morphology of the observed ionized gas ring is expected to be changed in the next several decades. The mean electron temperature and density of the ionized gas are $\bar{T}_{\mathrm{e}}=6800\pm 700\:$K and $\bar{n}_{\mathrm{e}}=6\times 10^{5}\:$cm−3, respectively. Then the mass of the ionized gas is estimated to be $M_{\mathrm{gas}}=4\times 10^{-4}\, M_{\odot }$.

scholarly journals Bar effect on gas-phase abundance gradients. I. Data sample and chemical abundances

2020 ◽  
Vol 500 (2) ◽  
pp. 2359-2379 ◽  
Author(s):  
A Zurita ◽  
E Florido ◽  
F Bresolin ◽  
E Pérez-Montero ◽  
I Pérez
Keyword(s):  
Emission Line ◽  
Gas Phase ◽  
Direct Method ◽  
Structural Parameters ◽  
Companion Paper ◽  
Strong Line ◽  
H Ii Regions ◽  
Chemical Abundances ◽  
The Galaxy ◽  
H Ii Region

ABSTRACT Studies of gas-phase radial metallicity profiles in spirals published in the last decade have diminished the importance of galactic bars as agents that mix and flatten the profiles, contradicting results obtained in the 1990s. We have collected a large sample of 2831 published H ii region emission-line fluxes in 51 nearby galaxies, including objects both with and without the presence of a bar, with the aim of revisiting the issue of whether bars affect the radial metal distribution in spirals. In this first paper of a series of two, we present the galaxy and the H ii region samples. The methodology is homogeneous for the whole data sample and includes the derivation of H ii region chemical abundances, structural parameters of bars and discs, galactocentric distances, and radial abundance profiles. We have obtained O/H and N/O abundance ratios from the Te-based (direct) method for a subsample of 610 regions, and from a variety of strong-line methods for the whole H ii region sample. The strong-line methods have been evaluated in relation to the Te-based one from both a comparison of the derived O/H and N/O abundances for individual H ii regions and a comparison of the abundance gradients derived from both methodologies. The median value and the standard deviation of the gradient distributions depend on the abundance method, and those based on the O3N2 indicator tend to flatten the steepest profiles, reducing the range of observed gradients. A detailed analysis and discussion of the derived O/H and N/O radial abundance gradients and y-intercepts for barred and unbarred galaxies is presented in the companion Paper II. The whole H ii region catalogue including emission-line fluxes, positions, and derived abundances is made publicly available on the CDS VizieR facility, together with the radial abundance gradients for all galaxies.

scholarly journals Molecular Line Observations of the Galactic Center Region

1989 ◽  
Vol 136 ◽  
pp. 129-133 ◽  
Author(s):  
A. A. Stark ◽  
J. Bally ◽  
R. W. Wilson ◽  
M. W. Pound
Keyword(s):  
Molecular Clouds ◽  
Virial Theorem ◽  
Galactic Center ◽  
Galactic Disk ◽  
High Mass ◽  
Molecular Gas ◽  
Molecular Line ◽  
Center Region ◽  
The Galaxy ◽  
Cloud Medium

A decade of galactic center observations at the Crawford Hill 7 m antenna is summarized. The galactic center region contains several hundred high-mass, high-density molecular clouds with physical properties very different from clouds in the outer galactic disk. There is also a considerable amount of molecular gas not bound into clouds, but sheared by differential rotation into a molecular inter-cloud medium not seen elsewhere in the Galaxy. These observations can be explained by a combination of the tidal density limit and the virial theorem. The distribution of emission on the sky and in velocity suggests that most of the dense gas is confined to a 500 pc long ridge of emission which may be a dust lane along the central bar.

scholarly journals SiO and H2O Masers in the Central Parsec of the Galaxy

1998 ◽  
Vol 164 ◽  
pp. 229-230 ◽  
Author(s):  
Karl M. Menten ◽  
Mark J. Reid
Keyword(s):  
Galactic Center ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Proper Motions ◽  
Infrared Images ◽  
Evolved Stars ◽  
The Galaxy ◽  
Sgr A ◽  
Central Parsec ◽  
Infrared Sources

AbstractWe have discovered maser emission from SiO and H2O molecules toward a number of evolved stars within the central parsec of our Galaxy. The maser positions can be registered with milliarcsecond precision relative to the radio continuum emission of the nonthermal Galactic center source Sgr A*. Since the masing stars are prominent infrared sources, our data can be used to locate the position of Sgr A* on infrared images of the Galactic center region. Using VLBA observations it will be possible to measure proper motions of the maser stars, which can be used to put constraints on the mass distribution in the central parsec.

scholarly journals A Survey of OH in the Galactic Centre Region

1996 ◽  
Vol 169 ◽  
pp. 311-316
Author(s):  
P.J. Boyce ◽  
R. J. Cohen
Keyword(s):  
Central Region ◽  
Molecular Clouds ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Galactic Centre ◽  
Molecular Gas ◽  
The Galaxy ◽  
Centre Region ◽  
Line Survey ◽  
The Continuum

The galactic centre contains the largest concentration of molecular clouds in the Galaxy. The clouds in the central region are unusual in having large linewidths and masses, and large non-circular motions. Previous surveys of their distribution in the central region have been carried out in OH (Robinson & McGee 1970; Cohen & Few 1976), H2CO (Whiteoak & Gardner 1979; Cohen & Few 1981), CO (Bania 1977; Dame et al. 1987; Bally et al. 1987, 1988) and CS (Bally et al. 1987, 1988). The OH groundstate lines at 18cm wavelength have certain advantages for such a survey. The OH lines appear in absorption against the galactic centre continuum sources, and against the continuum emission from the disk of the Galaxy. The absorption spectra are sensitive to relatively small molecular column densities. In addition they can give information on the relative positions of the molecular gas and the radio continuum sources. This paper describes results from an absorption line survey of the galactic centre region in the OH main lines at 1667.359 MHz and 1665.402 MHz (Boyce & Cohen 1994).

scholarly journals A Study of Dense Molecular Gas and Star Formation toward the Vela Molecular Ridge with NANTEN

1999 ◽  
Vol 51 (6) ◽  
pp. 775-790 ◽  
Author(s):  
Nobuyuki Yamaguchi ◽  
Norikazu Mizuno ◽  
Hiro Saito ◽  
Ken'ichi Matsunaga ◽  
Akira Mizuno ◽  
...  
Keyword(s):  
Star Formation ◽  
Total Mass ◽  
Massive Stars ◽  
Emission Lines ◽  
Molecular Gas ◽  
H Ii Regions ◽  
Molecular Outflow ◽  
Total Luminosity ◽  
Preceding Work ◽  
Order Of Magnitude

Abstract New observations of the J=1−0 12CO, 13CO, and C18O emission lines have been extensively made toward the Vela Molecular Ridge (VMR) with NANTEN. The most prominent cloud is the giant molecular cloud, corresponding to the VMR-C region (Vela C). The present C18O distribution has been identified as 29 clouds. Among them, the most massive one is included in Vela C, having a total mass of ∼ 4.4 × 104M⊙. The rest of them are smaller C18O clouds of 102-103M⊙. Star formation in the region is almost exclusively occurring in the C18O clouds. The luminosities of the associated protostellar IRAS sources range from 5 L⊙ to 1.1 × 104L⊙, and the luminosity distribution is found to be well represented by the relation dNstar/dLIR ∞ L-1.65±0.14IR. We find that the ratios of the total luminosity of the sources associated with given C18O clouds to the cloud masses are significantly enhanced for those clouds associated with H II regions by an order of magnitude. This is interpreted as meaning that the formation of massive stars is enhanced due to the effects of H II regions, as is consistent with the preceding work. We have also newly found molecular outflow toward IRAS 08588–4347 as well as five possible candidates for outflows.

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