Correlation search for dispersed radio emission from the galactic centre

AbstractDetecting and studying pulsars above a few GHz in the radio band is challenging due to the typical faintness of pulsar radio emission, their steep spectra, and the lack of observatories with sufficient sensitivity operating at high frequency ranges. Despite the difficulty, the observations of pulsars at high radio frequencies are valuable because they can help us to understand the radio emission process, complete a census of the Galactic pulsar population, and possibly discover the elusive population in the Galactic Centre, where low-frequency observations have problems due to the strong scattering. During the decades of the 1990s and 2000s, the availability of sensitive instrumentation allowed for the detection of a small sample of pulsars above 10 GHz, and for the first time in the millimetre band. Recently, new attempts between 3 and 1 mm (≈86 − 300 GHz) have resulted in the detections of a pulsar and a magnetar up to the highest radio frequencies to date, reaching 291 GHz (1.03 mm). The efforts continue, and the advent of new or upgraded millimetre facilities like the IRAM 30-m, NOEMA, the LMT, and ALMA, warrants a new era of high-sensitivity millimetre pulsar astronomy in the upcoming years.

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Synchrotron Bubbles and Radio Transients

Publications of the Astronomical Society of Australia ◽

10.1017/s132335800002600x ◽

1993 ◽

Vol 10 (4) ◽

pp. 342-345 ◽

Cited By ~ 4

Author(s):

Lewis Ball ◽

Michael Vlassis

Keyword(s):

Energy Spectrum ◽

Simple Model ◽

Radio Emission ◽

Galactic Centre ◽

Radio Flux ◽

Constant Energy ◽

Fundamental Feature ◽

Radio Transients ◽

Increasing Function

AbstractWe discuss a generalisation of the synchrotron bubble model which has been applied to short-lived radio transients which can peak and decay over just a few days. The assumptions of the simple model imply that when the flux is increasing with time, it must also be an increasing function of frequency. Observations of two recent radio transients, Nova Muscae 1991 and the Galactic Centre Transient, include the first data showing such a rising phase, and in both cases the radio flux was a decreasing function of frequency during the observed rising phases. Thus the simple synchrotron bubble model is inadequate, at least for these events. A fundamental feature of the simple model is the assumption that the process accelerating the radiating electrons ceases before the radio emission can escape. We relax this assumption by including an injection of electrons, with a constant energy spectrum, into the synchrotron bubble.

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The Observation and Interpretation of Radio Emission from Some Bright Galaxies

Australian Journal of Physics ◽

10.1071/ph550368 ◽

1955 ◽

Vol 8 (3) ◽

pp. 368 ◽

Cited By ~ 31

Author(s):

BY Mills

Keyword(s):

Radio Emission ◽

Globular Clusters ◽

Milky Way ◽

Magellanic Clouds ◽

Galactic Centre

Preliminary attempts to observe 13 bright southern galaxies are described. Of these 10 were detected, including the Magellanic Clouds. The latter were studied in detail. Supplementary measurements on the Milky Way near the galactic centre were made and also some unsuccessful attempts to observe two globular clusters.

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29. The discrete source of radio waves at the galactic centre

Symposium - International Astronomical Union ◽

10.1017/s0074180900049044 ◽

1957 ◽

Vol 4 ◽

pp. 166-168

Author(s):

F. G. Smith ◽

P. A. O'Brien ◽

J. E. Baldwin

Keyword(s):

Radio Emission ◽

Galactic Plane ◽

Discrete Source ◽

Resolving Power ◽

Galactic Centre ◽

Radio Waves ◽

Low Frequencies

The discrete source of radio emission in Sagittarius is among the most intense in the whole sky, but its situation in the belt of emission from ionized hydrogen and other sources associated with the galactic plane makes it difficult to observe. The observations described in this paper were made at frequencies of 38, 81·5, 210, and 500 Mc./s.; at these low frequencies it is particularly difficult to obtain sufficient aerial resolving power to distinguish the discrete source from the background. Interferometer aerials were therefore used, and at 38 and 210 Mc./s. spacings up to λ60 were used, sufficient to resolve the source completely. At 81·5 Mc./s. various sections of the large interferometer aerial were used.

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Kinematics of Molecules at the Galactic Centre

Symposium - International Astronomical Union ◽

10.1017/s007418090002684x ◽

1974 ◽

Vol 60 ◽

pp. 521-535 ◽

Cited By ~ 1

Author(s):

B. J. Robinson

Keyword(s):

Radio Emission ◽

Spectral Lines ◽

Strong Absorption ◽

Galactic Centre ◽

Lower Velocity ◽

Continuous Structure ◽

Direct Observations ◽

The Galaxy ◽

Nuclear Regions ◽

Co Emission

Dense gas clouds containing OH, CO, NH3 and H2CO are found in the inner part of the H1 nuclear disk. The molecular spectral lines allow direct observations of the kinematics of the gas near the galactic centre. Strong absorption of the thermal continuum sources by OH and H2CO shows that much of the gas on the near side of the centre can be located in a massive ‘ring’ expanding at 130 km s-1 which may have originated close to the nucleus about 106yr ago. Observations of CO emission from beyond the centre show that the far side of the ‘ring’ is expanding at a lower velocity, less than 90 km s-1. Observations of CO and NH3 emission with positive velocities for l < 360° are needed to establish whether the ‘ring’ is a continuous structure.OH and H2CO are also observed to be falling towards the centre. There is no agreement as to the location of this infalling matter.The nuclear regions of the Galaxy are compared with those of NGC 253, particularly in regard to expansional velocities, IR and radio emission, and OH absorption.

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Interstellar gas in the central region of the Galaxy

Symposium - International Astronomical Union ◽

10.1017/s0074180900101032 ◽

1967 ◽

Vol 31 ◽

pp. 239-251 ◽

Cited By ~ 3

Author(s):

F. J. Kerr

Keyword(s):

Central Region ◽

Galactic Plane ◽

Neutral Hydrogen ◽

Continuum Emission ◽

Galactic Centre ◽

Interstellar Gas ◽

Hydrogen Recombination ◽

The Galaxy ◽

Centre Region ◽

The Relationship

A review is given of information on the galactic-centre region obtained from recent observations of the 21-cm line from neutral hydrogen, the 18-cm group of OH lines, a hydrogen recombination line at 6 cm wavelength, and the continuum emission from ionized hydrogen.Both inward and outward motions are important in this region, in addition to rotation. Several types of observation indicate the presence of material in features inclined to the galactic plane. The relationship between the H and OH concentrations is not yet clear, but a rough picture of the central region can be proposed.

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Progress report on 21-cm observations at low latitude between longitudes (l 11) 0° and 66°

Symposium - International Astronomical Union ◽

10.1017/s0074180900100907 ◽

1967 ◽

Vol 31 ◽

pp. 177-179

Author(s):

W. W. Shane

Keyword(s):

Preliminary Report ◽

Progress Report ◽

Galactic Centre ◽

Low Latitude ◽

The Third ◽

Introductory Lecture ◽

Centre Region

In the course of several 21-cm observing programmes being carried out by the Leiden Observatory with the 25-meter telescope at Dwingeloo, a fairly complete, though inhomogeneous, survey of the regionl11= 0° to 66° at low galactic latitudes is becoming available. The essential data on this survey are presented in Table 1. Oort (1967) has given a preliminary report on the first and third investigations. The third is discussed briefly by Kerr in his introductory lecture on the galactic centre region (Paper 42). Burton (1966) has published provisional results of the fifth investigation, and I have discussed the sixth in Paper 19. All of the observations listed in the table have been completed, but we plan to extend investigation 3 to a much finer grid of positions.

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Observations of the continuum near the galactic centre

Symposium - International Astronomical Union ◽

10.1017/s0074180900101305 ◽

1967 ◽

Vol 31 ◽

pp. 405

Author(s):

F. J. Kerr

Keyword(s):

Galactic Centre ◽

The Past ◽

Centre Region ◽

The Continuum

A continuum survey of the galactic-centre region has been carried out at Parkes at 20 cm wavelength over the areal11= 355° to 5°,b11= -3° to +3° (Kerr and Sinclair 1966, 1967). This is a larger region than has been covered in such surveys in the past. The observations were done as declination scans.

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