X‐Ray Sources and Star Formation Activity in the Sagittarius B2 Cloud Observed with<i>Chandra</i>

Takagi, Saho; Murakami, Hiroshi; Koyama, K.

doi:10.1086/340499

Cited by 36 publications

(35 citation statements)

References 45 publications

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“…To calculate the 99 per cent confidence level MDP of the medium/hard X-ray instrument (see Marin et al 2012b Sidoli et al 2001;Terrier et al 2010) being close to the one of the Crab ( ∼ 2), in first approximation we can assume similar fluxes (in mCrab) in the MEP energy band if we neglect absorption below 8 keV. No observation of Sgr C has been made above 10 keV yet, but its soft X-ray continuum has been fitted with a ∼ 2 power law (Murakami et al 2001;Takagi-i., Murakami & Koyama 2002), similar to Sgr B2. Therefore, we assume for Sgr C a flux in the MEP energy band which is just scaled with respect to that of Sgr B2 by the same factor which is observed in the soft X-rays, that is, a factor of 3 fainter (Murakami et al 2000).…”

Section: Detectability With Available Technologymentioning

confidence: 99%

Prospects of 3D mapping of the Galactic Centre clouds with X-ray polarimetry

Marin

Karas

Kunneriath

et al. 2014

Monthly Notices of the Royal Astronomical Society

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Despite past panchromatic observations of the innermost part of the Milky Way, the overall structure of the Galactic Centre (GC) remains enigmatic in terms of geometry. In this paper, we aim to show how polarimetry can probe the three-dimensional position of the molecular material in the central ∼100 pc of the GC. We investigate a model where the central supermassive black hole Sgr A * is radiatively coupled to a fragmented circumnuclear disc (CND), an elliptical twisted ring representative of the central molecular zone (CMZ), and the two main, bright molecular clouds Sgr B2 and Sgr C. 8-35 keV integrated polarization mapping reveals that Sgr B2 and Sgr C, situated at the two sides of the CMZ, present the highest polarization degrees (66.5 and 47.8 per cent, respectively), both associated with a polarization position angle ψ = 90• (normal to the scattering plane). The CND shows a lower polarization degree, 1.0 per cent with ψ = −20.• 5, tracing the inclination of the CND with respect to the Galactic plane. The CMZ polarization is spatially variable. We also consider a range of spatial locations for Sgr A * and the reprocessing media, and investigate how the modelled three-dimensional geometry influences the resulting GC polarization. The two reflection nebulae are found to always produce high polarization degrees ( 10 per cent). We show that a 500 ks observation with a broad-band polarimeter could constrain the location and the morphology of the scattering material with respect to the emitting source, revealing the past activity of Sgr A * .

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Section: Detectability With Available Technologymentioning

confidence: 99%

Prospects of 3D mapping of the Galactic Centre clouds with X-ray polarimetry

Marin

Karas

Kunneriath

et al. 2014

Monthly Notices of the Royal Astronomical Society

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“…A similarly ambiguous situation exists in TC1 (Cernicharo et al 1998) where an outflow is not confirmed. The lack of perfect comparisons is due in part to the following reasons: some possible YSOs have X-ray emission but are not classified because they lack IR counterparts (Takagi et al 2002). In other cases, such as in R Mon, Preibisch et al (2002) showed that the IRS 3 X-ray sources were unlikely to be the outflow source (see also Kohno et al 2002).…”

Section: Ggd 27-xmentioning

confidence: 99%

GGD 27: X-Rays From a Massive Protostar With an Outflow

Pravdo

Tsuboi

Suzuki

et al. 2008

ApJ

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We report the discovery of a cluster of Class I protostars in GGD 27. One of these protostars is the previously known, centrally located, GGD 27-ILL, which powers a massive bipolar outflow. We show that GGD 27-ILL, which is known to be the bright infrared (IR) source, IRAS 18162-2048, and a compact radio continuum source, is also the newly discovered hard X-ray source, GGD 27-X. The observations were made with the ACIS instrument on the Chandra X-ray Observatory. The X-rays from GGD 27-X are variable when compared with 4 years earlier, with an unabsorbed 2-10 keV X-ray luminosity in this observation of 1.5-12 × 10 31 erg s −1 and a plasma temperature of 10 7 K. The X-rays are probably associated with the underlying B0 star (rather than outflowing material), providing a rare glimpse in hard X-rays of an optically obscured massive protostar with an outflow. The X-ray luminosity and spectrum appear to be consistent with stars of its type in other star formation regions. Several other variable X-ray sources are also detected in the IR cluster that contains GGD 27-X. We also discuss another nearby cluster. In each of the clusters there is an object that is X-ray hard, highly absorbed at low energies, in a blank optical/IR/radio field, and variable in X-ray intensity by a factor of 10 on a timescale of 4 years. These latter objects may arise from more recent episodes of star formation or may be "hidden" Class III sources.

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“…The bubble model has also been used to explain the coherent space velocities of water maser sources from the very source of G (Mac Low & Elitzur 1992), where it was proposed that these sources are from the expanding shells swept by stellar winds. The involvement of cold matter in the hard X-ray emission is strongly inferred by the detection of the fluorescent iron line in Sagittarius B2 and the Arches cluster (Takagi et al 2002;YusefZadeh et al 2002). Because this possibility for the X-ray emission has not been discussed in previous works, we examine this idea here in more detail.…”

Section: Wind-blown Bubblementioning

confidence: 99%

Hard X‐Rays from Ultracompact HiiRegions in W49A

Tsujimoto

Hosokawa

Feigelson

et al. 2006

ApJ

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We report the Chandra detection of hard X-ray emission from the Welch ring in W49A, an organized structure of ultracompact (UC ) H ii regions containing a dozen nascent early-type stars. Two UC H ii regions are associated with hard X-ray emission in a deep Advanced CCD Imaging Spectrometer (ACIS) image exposed for $96.7 ks. One of the two X-ray sources has no near-infrared counterpart and is extended by $5 00 , or $0.3 pc, at a distance of $11.4 kpc, which is spatially aligned with the cometary radio continuum emission associated with the UC H ii region. The X-ray spectrum of the emission, when fit with a thermal model, indicates a heavily absorbed plasma with extinction of $5 ; 10 23 cm À2 , temperature $7 keV, and X-ray luminosity in the 3.0Y8.0 keV band of $3;10 33 ergs s À1 . Both the luminosity and the size of the emission resemble the extended hard emission found in UC H ii regions in Sagittarius B2, yet they are smaller by an order of magnitude than the emission found in massive star clusters such as NGC 3603. Three possibilities are discussed for the cause of the hard extended emission in the Welch ring: an ensemble of unresolved point sources, shocked interacting winds of the young O stars, and a wind-blown bubble interacting with ambient cold matter. Subject headingg s: H ii regions -ISM: individual ( W49A) -radio continuum: ISM -stars: early-type -X-rays: ISM

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X‐Ray Sources and Star Formation Activity in the Sagittarius B2 Cloud Observed withChandra

Cited by 36 publications

References 45 publications

Prospects of 3D mapping of the Galactic Centre clouds with X-ray polarimetry

Prospects of 3D mapping of the Galactic Centre clouds with X-ray polarimetry

GGD 27: X-Rays From a Massive Protostar With an Outflow

Hard X‐Rays from Ultracompact HiiRegions in W49A

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