A VLA Survey for Compact Radio Sources in the Galactic Center

Lazio, T. Joseph W.; Cordes, J. M.

doi:10.1086/521676

Cited by 34 publications

(51 citation statements)

References 41 publications

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“…If – as consistent with the work of others based on the current stellar population (Serabyn & Morris 1996; Figer et al 2004; Figer 2008) or upper limits to the pulsar population (Lazio & Cordes 2008) – the current SFR has been sustained for multi‐Gyr time‐scales, the wind emerging from the GC and the CR ion population it carries compellingly explain the large‐angular‐scale, non‐thermal emission detected at microwave and ∼GeV energies.…”

Section: Discussionsupporting

confidence: 82%

“…We think it likely that, in fact, equipartition does not hold in the GC ISM. The relativistic electrons that escape the region on the wind can explain the large‐scale, diffuse radio emission detected from the Galaxy’s nuclear bulge (| l | < 3°), in particular their synchrotron emission explains the non‐thermal spectrum of what has been labelled in previous work the DNS (LaRosa et al 2005) and the GC lobe (Sofue & Handa 1984; Law 2010). We have not explained the majority of the apparently extended ∼ GeV emission from the region but much of this emission is due to point sources certainly including a source coincident with Sgr A* (Chernyakova et al 2011) with preliminary indications that, not unexpectedly, MSPs also make a large contribution to the extended emission. If – as consistent with the work of others based on the current stellar population (Serabyn & Morris 1996; Figer et al 2004; Figer 2008) or upper limits to the pulsar population (Lazio & Cordes 2008) – the current SFR has been sustained for multi‐Gyr time‐scales, the wind emerging from the GC and the CR ion population it carries compellingly explain the large‐angular‐scale, non‐thermal emission detected at microwave and ∼GeV energies.…”

Section: Discussionsupporting

confidence: 81%

“…The rates found above are consistent with that found by Lazio & Cordes (2008) and Deneva, Cordes & Lazio (2009) from their radio studies of pulsars and radio point source pulsar candidates in the inner 1 • of the Galaxy, viz. that the GC SN rate has a rough upper bound at 0.1 per century (for a continuous -rather than burstingstar formation history, as we favour; see below).…”

Section: B23 Sn Rate Upper Limit From Gc Pulsar Populationsupporting

confidence: 89%

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Wild at Heart: the particle astrophysics of the Galactic Centre

Crocker¹,

Jones²,

Aharonian³

et al. 2011

Monthly Notices of the Royal Astronomical Society

126

209

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We consider the high‐energy astrophysics of the inner ∼200 pc of the Galaxy. Our modelling of this region shows that the supernovae exploding here every few thousand years inject enough power to (i) sustain the steady‐state, in situ population of cosmic rays (CRs) required to generate the region’s non‐thermal radio and TeV γ‐ray emission; (ii) drive a powerful wind that advects non‐thermal particles out of the inner Galactic Centre; (iii) supply the low‐energy CRs whose Coulombic collisions sustain the temperature and ionization rate of the anomalously warm envelope detected throughout the Central Molecular Zone; (iv) accelerate the primary electrons which provide the extended, non‐thermal radio emission seen over ∼150 pc scales above and below the plane (the Galactic Centre lobe); and (v) accelerate the primary protons and heavier ions which, advected to very large scales (up to ∼10 kpc), generate the recently identified Wilkinson Microwave Anisotropy Probe (WMAP) haze and corresponding Fermi haze/bubbles. Our modelling bounds the average magnetic field amplitude in the inner few degrees of the Galaxy to the range 60 < B/μ G < 40 0 (at 2σ confidence) and shows that even TeV CRs likely do not have time to penetrate into the cores of the region’s dense molecular clouds before the wind removes them from the region. This latter finding apparently disfavours scenarios in which CRs – in this starburst‐like environment – act to substantially modify the conditions of star formation. We speculate that the wind we identify plays a crucial role in advecting low‐energy positrons from the Galactic nucleus into the bulge, thereby explaining the extended morphology of the 511 keV line emission. We present extensive appendices reviewing the environmental conditions in the Galactic Centre, deriving the star formation and supernova rates there, and setting out the extensive prior evidence that exists, supporting the notion of a fast outflow from the region.

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Section: Discussionsupporting

confidence: 82%

Section: Discussionsupporting

confidence: 81%

Section: B23 Sn Rate Upper Limit From Gc Pulsar Populationsupporting

confidence: 89%

See 1 more Smart Citation

Wild at Heart: the particle astrophysics of the Galactic Centre

Crocker¹,

Jones²,

Aharonian³

et al. 2011

Monthly Notices of the Royal Astronomical Society

126

209

View full text Add to dashboard Cite

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“…We compute spectral indices for all the 0.33 GHz sources based on detection of counterparts in the Galactic plane survey of radio sources at 1.4 GHz (White et al 2005) (hereafter, GPSR), or in the survey of compact sources towards the GC (Lazio & Cordes 2008) (hereafter, LC08). Spectral indices (α) for these sources have been computed following the convention of flux density (S) ∝ ν α between 1.4 and 0.33 GHz.…”

Section: Observations and Data Analysismentioning

confidence: 99%

Density of warm ionized gas near the Galactic center: low radio frequency observations

Roy¹

2013

Proc. IAU

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We have observed the Galactic Center (GC) region at 0.154 and 0.255 GHz with the GMRT. A total of 62 compact likely extragalactic sources are detected. Their scattering sizes go down linearly with increasing angular distance from the GC up to about 1 • . The apparent scattering sizes of sources are more than an order of magnitude down than predicted earlier by the NE2001 model of Galactic electron distribution within 359.5 • < l < 0.5 • and −0.5 • < b < 0.5 • (Hyperstrong scattering region) of the Galaxy. High free-free optical depths (τ ) are observed towards most of the extended nonthermal sources within 0.6 • from the GC. Significant variation of τ indicate the absorbing medium is patchy at an angular scale of ∼10 ′ and n e is ∼ 10.cm −3 that matches with the NE2001 model. This model predicts the extragalactic (EG) sources to be resolved out from 1.4 GHz interferometric surveys. However, 8 likely EG sources out of 10 expected in the region are present in 1.4 GHz catalog. Ionized interfaces of dense molecular clouds to the ambient medium are most likely responsible for strong scattering and low radio frequency absorption. However, dense GC clouds traced by CS J = 1 − 0 emission are found to have a narrow distribution of ∼ 0.2 • across the Galactic plane. Angular distribution of most of the EG sources seen through the so called Hyperstrong scattering region are random in b, and typically ∼7 out of 10 sources will not be seen through to the dense molecular clouds, and it explains why most of them are not scatter broadened at 1.4 GHz.

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“…An alternative, potentially more efficient, approach is to begin by initially identifying candidates in the image plane (Cordes & Lazio 1997;Lazio & Cordes 2008), and then later followed up with deep radio pulsations searches at higher frequencies. Pulsar candidates can be recognized in the image plane as compact, steep spectrum (polarized) radio sources.…”

Section: Introductionmentioning

confidence: 99%

Searching for pulsars associated with the Fermi GeV excess

Bhakta

Deneva

Frail

et al. 2017

Monthly Notices of the Royal Astronomical Society

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The Fermi Large Area Telescope has detected an extended region of GeV emission toward the Galactic Center that is currently thought to be powered by dark matter annihilation or a population of young and/or millisecond pulsars. In a test of the pulsar hypothesis, we have carried out an initial search of a 20 deg 2 area centered on the peak of the galactic center GeV excess. Candidate pulsars were identified as a compact, steep spectrum continuum radio source on interferometric images and followed with targeted single-dish pulsation searches. We report the discovery of the recycled pulsar PSR 1751−2737 with a spin period of 2.23 ms. PSR 1751−2737 appears to be an isolated recycled pulsar located within the disk of our Galaxy, and it is not part of the putative bulge population of pulsars that are thought to be responsible for the excess GeV emission. However, our initial success in this small pilot survey suggests that this hybrid method (i.e. wide-field interferometric imaging followed up with single dish pulsation searches) may be an efficient alternative strategy for testing whether a putative bulge population of pulsars is responsible for the GeV excess.

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A VLA Survey for Compact Radio Sources in the Galactic Center

Cited by 34 publications

References 41 publications

Wild at Heart: the particle astrophysics of the Galactic Centre

Wild at Heart: the particle astrophysics of the Galactic Centre

Density of warm ionized gas near the Galactic center: low radio frequency observations

Searching for pulsars associated with the Fermi GeV excess

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