scholarly journals Radio continuum and radio recombination line observations of the Galactic center lobe

2013 ◽  
Vol 9 (S303) ◽  
pp. 129-131
Author(s):  
Halca Nagoshi ◽  
Kenta Fujisawa ◽  
Yuzo Kubose
Keyword(s):  
Electron Temperature ◽  
Galactic Center ◽  
Thermal Emission ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Recombination Line ◽  
Ionized Gas ◽  
Radio Recombination Line ◽  
Spatial Coverage ◽  
The Continuum

AbstractRadio continuum (cont) and radio recombination line (RRL) observations with the Yamaguchi 32-m radio telescope toward the lower part of the Galactic center lobe (GCL) in the Galactic center region are presented. While two ridges of the GCL were seen in both continuum and RRL images, the spatial coverage of the ridges of the continuum and RRL is not coincident. We distinguish the continuum emission of the GCL into thermal and non-thermal emission by assuming an electron temperature of the ionized gas of 4370 K, estimated based on the line width (14.1 km s−1). The thermal emission was found to be located inside and surrounded by the non-thermal 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 The Galactic center lobe filled with thermal plasma

2019 ◽  
Vol 71 (4) ◽  
Author(s):  
Halca Nagoshi ◽  
Yuzo Kubose ◽  
Kenta Fujisawa ◽  
Kazuo Sorai ◽  
Yoshinori Yonekura ◽  
...  
Keyword(s):  
Thermal Plasma ◽  
Galactic Center ◽  
Galactic Plane ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Galactic Rotation ◽  
Observational Result ◽  
Recombination Line ◽  
The North ◽  
Radio Recombination Line

Abstract An observational result of a radio continuum and H92α radio recombination line of the Galactic center lobe (GCL), using the Yamaguchi 32 m radio telescope, is reported. The obtained spatial intensity distribution of the radio recombination line shows two distinctive ridge-like structures extending from the Galactic plane vertically to the north at the eastern and western sides of the Galactic center, which are connected to each other at a latitude of ${1{^{\circ}_{.}}2}$ to form a loop-like structure as a whole. This suggests that most of the radio continuum emission of the GCL is free–free emission, and that the GCL is filled with thermal plasma. The east ridge of the GCL observed with the radio recombination line separates 30 pc from the radio arc, which has been considered a part of the GCL, but coincides with a ridge of the radio continuum at a Galactic longitude of 0°. The radial velocity of the radio recombination line is found to be between −4 and +10 km s−1 across the GCL. This velocity is much smaller than expected from the Galactic rotation, and hence indicates that the GCL exists apart from the Galactic center. These characteristics of the GCL suggest that the long-standing hypothesis that the GCL was created by explosive activity in the Galactic center is unlikely, but favor that the GCL is a giant H ii region.

scholarly journals Radio observations of evaporating objects in the Cygnus OB2 region

2019 ◽  
Vol 627 ◽  
pp. A58 ◽  
Author(s):  
N. L. Isequilla ◽  
M. Fernández-López ◽  
P. Benaglia ◽  
C. H. Ishwara-Chandra ◽  
S. del Palacio
Keyword(s):  
Thermal Emission ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Spectral Indices ◽  
Ionized Gas ◽  
Low Frequencies ◽  
Thermal Origin ◽  
Index Maps ◽  
Photoionization Rate ◽  
Gas Component

We present observations of the Cygnus OB2 region obtained with the Giant Metrewave Radio Telescope (GMRT) at frequencies of 325 and 610 MHz. In this contribution we focus on the study of proplyd-like objects (also known as free-floating evaporating gas globules or frEGGs) that typically show an extended cometary morphology. We identify eight objects previously studied at other wavelengths and derive their physical properties by obtaining their optical depth at radio-wavelengths. Using their geometry and the photoionization rate needed to produce their radio-continuum emission, we find that these sources are possibly ionized by a contribution of the stars Cyg OB2 #9 and Cyg OB2 #22. Spectral index maps of the eight frEGGs were constructed, showing a flat spectrum in radio frequencies in general. We interpret these as produced by optically thin ionized gas, although it is possible that a combination of thermal emission, not necessarily optically thin, produced by a diffuse gas component and the instrument response (which detects more diffuse emission at low frequencies) can artificially generate negative spectral indices. In particular, for the case of the Tadpole we suggest that the observed emission is not of non-thermal origin despite the presence of regions with negative spectral indices in our maps.

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.

Metallicity Structure across the Galactic Disk: Radio Observations of H ii Regions

2017 ◽  
Vol 13 (S334) ◽  
pp. 275-276
Author(s):  
Dana S. Balser ◽  
Trey V. Wenger ◽  
T. M. Bania ◽  
L. D. Anderson
Keyword(s):  
Electron Temperature ◽  
Massive Star ◽  
Galactic Disk ◽  
Radio Continuum ◽  
Continuum Emission ◽  
H Ii Regions ◽  
Thermal Electron ◽  
Radio Recombination Line ◽  
Nuclear Processing ◽  
Metallicity Distribution

AbstractHii regions are the sites of massive star formation and are the archetypal tracers of spiral arms. Because of their short lifetimes (&lt;10 Myr) their abundances provide a measure of the nuclear processing of many stellar generations. Here we review our ongoing efforts to explore the metallicity structure of the Galactic disk by observing radio recombination line (RRL) and thermal radio continuum emission toward Hii regions. The RRL-to-continuum ratio provides an accurate measure of the electron temperature which is used as a proxy for metallicity. Since collisionally excited lines from metals (e.g., O, C) are the main coolant in Hii regions, the thermal electron temperature is well correlated with metallicity (e.g., [O/H]). We determine Hii region distances from maser parallax measurements when possible; otherwise we use kinematic distances. Such radio diagnostics of Hii regions yield an extinction free tracer to map the metallicity distribution across the entire Galactic disk.

scholarly journals Multi-Array λ2 and 6cm Radio Continuum Observations of Sgr A West

1989 ◽  
Vol 136 ◽  
pp. 443-451 ◽  
Author(s):  
F. Yusef-Zadeh ◽  
Mark Morris ◽  
Ron Ekers
Keyword(s):  
Spectral Index ◽  
Stellar Wind ◽  
Galactic Center ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Spectral Indices ◽  
Ionized Gas ◽  
Sgr A ◽  
Index Maps ◽  
East West

Sub-arcsecond (down to 0.1″ × 0.2″) radio continuum observations using the VLA2 in a number of configurations have been carried out in order to investigate the fine-scale morphological details of the ionized gas and the distribution of spectral index along the triskelian-shaped figure of Sgr A West. In addition to finding a number of isolated patches of thermally-emitting gas and an absorbing feature at λ6cm within three arcminutes of the Galactic center, we have observed:1) radio continuum emission from IRS-7, implying that the stellar wind from this supergiant is externally ionized. An improved position for this object was obtained.2) the circular mini-cavity located along the east-west bar of Sgr A West. This feature has a diameter of 2-arcseconds and may have been created by a spherical wind, the source of which is yet to be identified; the seemingly most plausible candidate, IRS-16, is offset by 3″ from the center of the cavity.Spectral index maps having a resolution of 0.7″ × 0.3″ were made from scaled array observations at λ2cm and 6cm. They show that the eastern arm has a spectral index near −0.1, while the northern arm and the bar have positive spectral indices, indicating perhaps a partial opacity effect. The spectral index of IRS-7 is +0.6, consistent with that expected from a completely ionized stellar wind.

scholarly journals Radio Continuum and Recombination Line Studies of the Galactic Center

1974 ◽  
Vol 60 ◽  
pp. 477-489 ◽  
Author(s):  
M. A. Gordon
Keyword(s):  
Galactic Center ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Recombination Line ◽  
Radio Observations ◽  
To Come

This review discusses unsuccessful searches for electromagnetic bursts accompanying gravitational events observed to come from the galactic center, radio observations of continuum emission and recombination lines from the region of the galactic center.

scholarly journals HII regions and star formation in the galactic center

1979 ◽  
Vol 84 ◽  
pp. 357-366 ◽  
Author(s):  
P. G. Mezger ◽  
T. Pauls
Keyword(s):  
Thermal Radiation ◽  
High Frequency ◽  
Galactic Center ◽  
Thermal Emission ◽  
Hii Regions ◽  
Radio Continuum ◽  
Line Of Sight ◽  
Low Density ◽  
Recombination Line ◽  
Half Power

The centimeter wavelength continuum radiation seen toward the Galactic center (Figure 1) is a mixture of thermal (free-free) and nonthermal (synchrotron) radiation which originates in the nucleus and along the line-of-sight. In this review we discuss only the thermal emission (also see Mezger 1974 and Oort 1977). High-frequency radio continuum and recombination line observations show that the thermal radiation comes from extend, low-density (ELD) HII, and a number of giant “radio HII regions” (see Mezger 1978 for definitions). The approximate half-power contour of the ELD HII (labelled EI in Fig. 1), probably represents a superposition of evolved and expanded HII regions. Thermal radiation outside EI comes predominantly from along the line-of-sight (see Pauls and Mezger 1975).

scholarly journals HCO+and Radio Continuum Emission from the Star Forming Region G75.78+0.34

2014 ◽  
Vol 2014 ◽  
pp. 1-5
Author(s):  
Rogemar A. Riffel ◽  
Everton Lüdke
Keyword(s):  
Massive Star ◽  
Emission Measure ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Ionized Gas ◽  
Very Large Array ◽  
Star Forming ◽  
Molecular Outflows ◽  
H Ii Region ◽  
The Continuum

We present 1.3 and 3.6 cm radio continuum images and a HCO+spectrum of the massive star forming region G75.78+0.34 obtained with the Very Large Array (VLA) and with the Berkley Illinois Maryland Association (BIMA) interferometer. Three structures were detected in the continuum emission: one associated with the well-known cometary H ɪɪ region, plus two more compact structures located at 6′′ east and at 2′′ south of cometary H ɪɪ region. Using the total flux and intensity peak we estimated an electron density of≈1.5 × 104 cm−3, an emission measure of≈6 × 107 cm−6 pc, a mass of ionized gas of≈3 M⊙, and a diameter of 0.05 pc for the cometary H ɪɪ region, being typical values for an ultracompact H ɪɪ region. The HCO+emission probably originates from the molecular outflows previously observed in HCN and CO.

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