The Hot Gas in the Galactic Bulge

X-ray imaging spectroscopic observations near the Galactic center region were carried out with the ASCA satellite. We found two bright spots very close to the Galactic center (Sgr A∗); one is extended and has a soft spectrum associated with strong emission lines from highly ionized irons, while the other is a point-like object with a harder spectrum and a larger absorption. We also found extended emission with K-shell transition lines from highly ionized Si, S, Ar, Ca and Fe. Remarkable feature found with ASCA is an extended emission of 6.4 keV lines of low ionization irons. The 6.4 keV line fluxes are found to be well correlated to the region of cool clouds. We interpret that the 6.4 keV line is due to florescence from the cool clouds irradiated by strong (and obscured from our line of sight) X-ray beams.

Download Full-text

X-ray polarimetry – A new Window on Black Hole Systems

Proceedings of the International Astronomical Union ◽

10.1017/s1743921317003416 ◽

2016 ◽

Vol 12 (S324) ◽

pp. 338-341

Author(s):

René W. Goosmann

Keyword(s):

Black Hole ◽

Binary Systems ◽

Galactic Center ◽

Galactic Nuclei ◽

High Energy ◽

X Ray ◽

X Ray Imaging ◽

History Of ◽

Imaging Polarimetry ◽

High Energy Emission

AbstractThree dedicated X-ray polarimetry mission projects are currently under phase A study at NASA and ESA. The need for this new observational window is more apparent than ever. On behalf of the consortium behind the X-ray Imaging Polarimetry Explorer (XIPE) we present here some prospects of X-ray polarimetry for our understanding of supermassive and stellar mass black hole systems. X-ray polarimetry is going to discriminate between leptonic and hadronic jet models in radio-loud active galactic nuclei. For leptonic jets it also puts important constraints on the origin of the seed photons that constitute the high energy emission via Comptonization. Another important application of X-ray polarimetry allows us to clarify the accretion history of the supermassive black hole at the Galactic Center. In a few Black Hole X-ray binary systems, X-ray polarimetry allows us to estimate in a new, independent way the angular momentum of the black hole.

Download Full-text

Reflection nebulae in the Galactic center: soft X-ray imaging polarimetry

Astronomy and Astrophysics ◽

10.1051/0004-6361/201425341 ◽

2015 ◽

Vol 576 ◽

pp. A19 ◽

Cited By ~ 11

Author(s):

F. Marin ◽

F. Muleri ◽

P. Soffitta ◽

V. Karas ◽

D. Kunneriath

Keyword(s):

Galactic Center ◽

X Ray ◽

X Ray Imaging ◽

Imaging Polarimetry ◽

Reflection Nebulae

Download Full-text

The Sgr B2 X‐Ray Echo of the Galactic Center Supernova Explosion that Produced Sgr A East

The Astrophysical Journal ◽

10.1086/498968 ◽

2006 ◽

Vol 638 (2) ◽

pp. 786-796 ◽

Cited By ~ 19

Author(s):

Christopher L. Fryer ◽

Gabriel Rockefeller ◽

Aimee Hungerford ◽

Fulvio Melia

Keyword(s):

Galactic Center ◽

Supernova Explosion ◽

X Ray ◽

Sgr A

Download Full-text

Chandra observations of the X-ray emission from Molecular Clouds at the Galactic Center related to Sgr A* past activity

10.22323/1.176.0106 ◽

2013 ◽

Author(s):

Maica Clavel ◽

Regis Terrier ◽

Andrea Goldwurm ◽

Mark Morris ◽

G. Ponti ◽

...

Keyword(s):

Molecular Clouds ◽

Galactic Center ◽

X Ray ◽

Sgr A ◽

Past Activity

Download Full-text

Tracing the Milky Way’s Vestigial Nuclear Jet

The Astrophysical Journal ◽

10.3847/1538-4357/ac224f ◽

2021 ◽

Vol 922 (2) ◽

pp. 254

Author(s):

Gerald Cecil ◽

Alexander Y. Wagner ◽

Joss Bland-Hawthorn ◽

Geoffrey V. Bicknell ◽

Dipanjan Mukherjee

Keyword(s):

Galactic Center ◽

Galactic Plane ◽

Hubble Space Telescope ◽

Seyfert Galaxy ◽

Radio Continuum ◽

X Ray ◽

Multiple Paths ◽

Ngc 1068 ◽

Sgr A ◽

Hydrodynamical Simulations

Abstract MeerKAT radio continuum and XMM-Newton X-ray images have recently revealed a spectacular bipolar channel at the Galactic Center that spans several degrees (∼0.5 kpc). An intermittent jet likely formed this channel and is consistent with earlier evidence of a sustained, Seyfert-level outburst fueled by black hole accretion onto Sgr A* several Myr ago. Therefore, to trace a now weak jet that perhaps penetrated, deflected, and percolated along multiple paths through the interstellar medium, relevant interactions are identified and quantified in archival X-ray images, Hubble Space Telescope Paschen α images and Atacama Large Millimeter/submillimeter Array millimeter-wave spectra, and new SOAR telescope IR spectra. Hydrodynamical simulations are used to show how a nuclear jet can explain these structures and inflate the ROSAT/eROSITA X-ray and Fermi γ-ray bubbles that extend ± 75° from the Galactic plane. Thus, our Galactic outflow has features in common with energetic, jet-driven structures in the prototypical Seyfert galaxy NGC 1068.

Download Full-text

Deep XMM-Newton observations of the northern disc of M31

Astronomy and Astrophysics ◽

10.1051/0004-6361/201937008 ◽

2020 ◽

Vol 637 ◽

pp. A12

Author(s):

Patrick J. Kavanagh ◽

Manami Sasaki ◽

Dieter Breitschwerdt ◽

Miguel A. de Avillez ◽

Miroslav D. Filipović ◽

...

Keyword(s):

Massive Stars ◽

Low Density ◽

Plasma Properties ◽

X Ray ◽

Star Forming ◽

Hot Gas ◽

Grand Design ◽

Multi Wavelength ◽

Multi Phase ◽

Extended Emission

Aims. We use new deep XMM-Newton observations of the northern disc of M31 to trace the hot interstellar medium (ISM) in unprecedented detail and to characterise the physical properties of the X-ray emitting plasmas. Methods. We used all XMM-Newton data up to and including our new observations to produce the most detailed image yet of the hot ISM plasma in a grand design spiral galaxy such as our own. We compared the X-ray morphology to multi-wavelength studies in the literature to set it in the context of the multi-phase ISM. We performed spectral analyses on the extended emission using our new observations as they offer sufficient depth and count statistics to constrain the plasma properties. Data from the Panchromatic Hubble Andromeda Treasury were used to estimate the energy injected by massive stars and their supernovae. We compared these results to the hot gas properties. Results. The brightest emission regions were found to be correlated with populations of massive stars, notably in the 10 kpc star-forming ring. The plasma temperatures in the ring regions are ~0.2 up to ~0.6 keV. We suggest this emission is hot ISM heated in massive stellar clusters and superbubbles. We derived X-ray luminosities, densities, and pressures for the gas in each region. We also found large extended emission filling low density gaps in the dust morphology of the northern disc, notably between the 5 and 10 kpc star-forming rings. We propose that the hot gas was heated and expelled into the gaps by the populations of massive stars in the rings. Conclusions. It is clear that the massive stellar populations are responsible for heating the ISM to X-ray emitting temperatures, filling their surroundings, and possibly driving the hot gas into the low density regions. Overall, the morphology and spectra of the hot gas in the northern disc of M31 is similar to other galaxy discs.

Download Full-text

Molecular gas in the immediate vicinity of Sgr A* seen with ALMA

Proceedings of the International Astronomical Union ◽

10.1017/s1743921316012126 ◽

2016 ◽

Vol 11 (S322) ◽

pp. 129-132

Author(s):

Lydia Moser ◽

Álvaro Sánchez-Monge ◽

Andreas Eckart ◽

Miguel A. Requena-Torres ◽

Macarena García-Marin ◽

...

Keyword(s):

Galactic Center ◽

Line Emission ◽

Molecular Gas ◽

Future Studies ◽

X Ray ◽

Circumnuclear Disk ◽

Sgr A ◽

Central Parsec ◽

Cloud Cores ◽

Cold Core

AbstractWe report serendipitous detections of line emission with ALMA in band 3, 6, and 7 in the central parsec of the Galactic center at an up to now highest resolution (<0.7″). Among the highlights are the very first and highly resolved images of sub-mm molecular emission of CS, H13CO+, HC3N, SiO, SO, C2H, and CH3OH in the immediate vicinity (~1″ in projection) of Sgr A* and in the circumnuclear disk (CND). The central association (CA) of molecular clouds shows three times higher CS/X (X: any other observed molecule) luminosity ratios than the CND suggesting a combination of higher excitation - by a temperature gradient and/or IR-pumping - and abundance enhancement due to UV- and/or X-ray emission. We conclude that the CA is closer to the center than the CND is and could be an infalling clump consisting of denser cloud cores embedded in diffuse gas. Moreover, we identified further regions in and outside the CND that are ideally suited for future studies in the scope of hot/cold core and extreme PDR/XDR chemistry and consequent star formation in the central few parsecs.

Download Full-text

On the past activity of Sgr A*

Proceedings of the International Astronomical Union ◽

10.1017/s174392131400088x ◽

2013 ◽

Vol 9 (S303) ◽

pp. 333-343 ◽

Cited By ~ 1

Author(s):

G. Ponti ◽

M. R. Morris ◽

M. Clavel ◽

R. Terrier ◽

A. Goldwurm ◽

...

Keyword(s):

Strong Evidence ◽

Galactic Center ◽

Galactic Disk ◽

X Ray ◽

The Past ◽

Sgr A ◽

Past Activity

AbstractRecent X-ray emission events in the Galactic center would be expected to generate an X-ray reflection response within the surrounding clouds of the central molecular zone, in the Galactic disk and even, if powerful enough, in clouds outside our Galaxy. We review here the current constraints on Sgr A*'s past activity obtained through this method, with particular emphasis on the strong evidence that has been gathered for multiple X-ray flashes during the past few hundred years.

Download Full-text

Prospects for IXPE and eXTP polarimetric archaeology of the reflection nebulae in the Galactic center

Astronomy and Astrophysics ◽

10.1051/0004-6361/202037886 ◽

2020 ◽

Vol 643 ◽

pp. A52

Author(s):

L. Di Gesu ◽

R. Ferrazzoli ◽

I. Donnarumma ◽

P. Soffitta ◽

E. Costa ◽

...

Keyword(s):

Molecular Clouds ◽

Galactic Center ◽

Region Of Interest ◽

Polarization Degree ◽

Polarization Angle ◽

Diffuse Emission ◽

X Ray ◽

X Ray Imaging ◽

Spread Function ◽

Reflection Nebulae

The X-ray polarization properties of the reflection nebulae in the Galactic center inform us about the direction of the illuminating source (through the polarization angle) and the cloud position along the line of sight (through the polarization degree). However, the detected polarization degree is expected to be lowered because the polarized emission of the clouds is mixed with the unpolarized diffuse emission that permeates the Galactic center region. In a real observation, also the morphological smearing of the source due to the point spread function and the unpolarized instrumental background contribute in diluting the polarization degree. So far, these effects have never been included in the estimation of the dilution. We evaluate the detectability of the X-ray polarization predicted for the MC2, Bridge-B2, G0.11-0.11, Sgr B2, Sgr C1, Sgr C2, and Sgr C3 molecular clouds with modern X-ray imaging polarimeters such as the Imaging X-ray Polarimetry Explorer (IXPE), which is expected to launch in 2021, and the Enhanced X-ray Timing and Polarimetry mission (eXTP), whose launch is scheduled for 2027. We perform realistic simulations of X-ray polarimetric observations considering (with the aid of Chandra maps and spectra) the spatial, spectral, and polarization properties of all the diffuse emission and background components in each region of interest. We find that in the 4.0–8.0 keV band, where the emission of the molecular clouds outshines the other components, the dilution of the polarization degree, including the contribution due to the morphological smearing of the source, ranges between ~19% and ~55%. We conclude that for some distance values reported in the literature, the diluted polarization degree of G0.11-0.11, Sgr B2, Bridge-B2, Bridge-E, Sgr C1, and Sgr C3 may be detectable in a 2 Ms long IXPE observations. With the same exposure time, and considering the whole range of possible distances reported in the literature, the enhanced capabilities of eXTP may allow detecting the 4.0–8.0 keV of all the targets considered here.

Download Full-text