scholarly journals Constraints on high-J CO emission lines in z ∼ 6 quasars

2019 ◽  
Author(s):  
S Carniani ◽  
S Gallerani ◽  
L Vallini ◽  
A Pallottini ◽  
M Tazzari ◽  
...  
Keyword(s):  
Black Body ◽  
Continuum Emission ◽  
Molecular Gas ◽  
X Ray ◽  
Compact Region ◽  
Upper Limits ◽  
Gas Heating ◽  
Co Emission ◽  
Co Observations ◽  
The Continuum

Abstract We present Atacama Large Millimiter/submillimiter Array (ALMA) observations of eight highly excited CO (${\rm J_{\rm up}}$ >8) lines and continuum emission in two z ∼ 6 quasars: SDSS J231038.88+185519.7 (hereafter J2310), for which CO(8-7), CO(9-8), and CO(17-16) lines have been observed, and ULAS J131911.29+095951.4 (J1319), observed in the CO(14-13), CO(17-16) and CO(19-18) lines. The continuum emission of both quasars arises from a compact region (<0.9 kpc). By assuming a modified black-body law, we estimate dust masses of Log(Mdust/M⊙) = 8.75 ± 0.07 and Log(Mdust/M⊙) = 8.8 ± 0.2 and dust temperatures of Tdust = 76 ± 3 K and $T_{\rm dust}=66^{+15}_{-10}~{\rm K}$, respectively for J2310 and J1319. Only CO(8-7) and CO(9-8) in J2310 are detected, while 3σ upper limits on luminosities are reported for the other lines of both quasars. The CO line luminosities and upper limits measured in J2310 and J1319 are consistent with those observed in local AGN and starburst galaxies, and other z ∼ 6 quasars, except for SDSS J1148+5251 (J1148), the only quasar at z = 6.4 with a previous CO(17-16) line detection. By computing the CO SLEDs normalised to the CO(6-5) line and FIR luminosities for J2310, J1319, and J1149, we conclude that different gas heating mechanisms (X-ray radiation and/or shocks) may explain the different CO luminosities observed in these z ∼ 6 quasar. Future ${\rm J_{\rm up}}$ >8 CO observations will be crucial to understand the processes responsible for molecular gas excitation in luminous high-z quasars.

scholarly journals The Origin of Continuum Emission in Active Galactic Nuclei

1994 ◽  
Vol 159 ◽  
pp. 5-16 ◽  
Author(s):  
Joel N. Bregman
Keyword(s):  
Accretion Disk ◽  
Near Infrared ◽  
Galactic Nuclei ◽  
Black Body ◽  
Continuum Emission ◽  
Radiation Mechanism ◽  
X Ray ◽  
Pair Plasma ◽  
Inverse Compton ◽  
The Continuum

The general understanding of the continuum emission from AGN has changed from the picture where nonthermal processes were responsible for all of the emission. The current body of observation indicates that there are two types of objects, one being the blazar class (or blazar component), where nearly all of the emission is nonthermal, due primarily to synchrotron and inverse Compton emission. Variability studies indicate that the emitting region decreases with size from the radio through the X-ray region, where the size of the X-ray region is of order a light hour. More than two dozen of these radio-loud AGNs have been detected at GeV energies (one source at TeV energies), for which the radiation mechanism may be inverse Compton mechanism.In the other class, the radio-quiet AGN (component), the emission is almost entirely thermal, with radiation from dust dominating the near infrared to submillimeter region. The optical to soft X-ray emission is often ascribed to black body emission from an opaque accretion disk, but variability studies may not be consistent with expectations. Another attractive model has free-free emission being responsible for the optical to soft X-ray emission. The highest frequencies at which these AGN are detected is the MeV range, and these data should help to determine if this emission is produced in a scattering atmosphere, such as that around an accretion disk, or by another model involving an opaque pair plasma.

scholarly journals Evolution and State of the Local ISM

1996 ◽  
Vol 171 ◽  
pp. 442-442
Author(s):  
T. Schmutzler ◽  
D. Breitschwerdt
Keyword(s):  
Basic Feature ◽  
Emission Lines ◽  
Continuum Emission ◽  
Ionization Equilibrium ◽  
X Ray ◽  
Self Consistent ◽  
X Ray Background ◽  
Collisional Ionization ◽  
Consistent Approach ◽  
The Continuum

The most puzzling observations concerning the LISM (distance < 100 pc) can be explained by a fast adiabatically cooled gas in the cavity of an old superbubble. The ultrasoft X-ray background and contributions to the C- and M-bands are due to the continuum emission of delayed recombination [1]. In contrast to collisional ionization equilibrium (CIE) models, but consistent with recent observations [2], our model predicts a lack of emission lines and a low emissivity in the EUV range. In the figure below we compare the emissivities resulting from CIE at T = 106 K and those from our model at T = 4.2 × 104 K. The basic feature of our model is a thermally self-consistent approach of the time-dependent evolution.

scholarly journals X-ray Spectroscopy of the Ultra-soft Transient 4U1543-47

1990 ◽  
Vol 115 ◽  
pp. 205-208
Author(s):  
H. van der Woerd ◽  
N.E. White ◽  
S.M. Kahn
Keyword(s):  
Emission Line ◽  
Compact Object ◽  
Relativistic Effects ◽  
Emission Feature ◽  
Continuum Emission ◽  
X Ray ◽  
Black Hole Candidate ◽  
Transmission Grating ◽  
Cool Plasma ◽  
The Continuum

AbstractThe X-ray transient 4U1543-47 was observed in 1983 by the EXOSAT observatory near the maximum of an outburst. The X-ray spectrum was measured using a gas scintillation proportional counter (GSPC) and a transmission grating spectrometer (TGS). Two emission line features are resolved. A broad (FWHM ~2.7 keV) line at 5.9 keV is detected in the GSPC, which we interprete as a redshifted and broadened iron Kα line. The Une broadening and redshift may arise from either Compton scattering in a cool plasma with small optical depth (τ ≈ 5), or from Doppler and relativistic effects in the vicinity of a compact object. The spectrum below 2 keV, obtained with the TGS, shows evidence for a broad emission line feature at 0.74 keV, which may be an iron L-transition complex. However, we find that such an emission feature could be an artifact caused by an anomalously low interstellar absorption by neutral Oxygen. The continuum emission is extremely soft and is well described by an unsaturated Comptonized spectrum from a very cool plasma (kT = 0.84 keV) with large scattering depth (τ ≈ 27). The continuum spectrum is strikingly similar to that of black hole candidate LMC X-3.

scholarly journals FUV and optical spectrophotometry of X-ray selected Seyferts

1986 ◽  
Vol 119 ◽  
pp. 347-348
Author(s):  
J. T. Clarke ◽  
S. Bowyer ◽  
M. Grewing
Keyword(s):  
Seyfert Galaxies ◽  
Continuum Emission ◽  
Balmer Line ◽  
X Ray ◽  
Positive Correlation ◽  
Optical Spectrophotometry ◽  
Distinguishing Features ◽  
The Continuum

Nearly simultaneous FUV and optical spectrophotometry of X-ray selected Seyfert galaxies has revealed an average Ly α/H β ratio of 22, a positive correlation between the ratio Ly α/H β and the width of the lines, and additional Ly α emission in the wings of one source which is not matched by emission in the Balmer line wings. However, we find no distinguishing features in the continuum emission from these X-ray selected objects compared with other samples. If the correlation between Ly α/H β and the width of the lines is found to apply to larger samples of Seyferts, it may be that our objects appear Ly α bright because they are also broad-lined compared with other samples.

Upper Limits on the Continuum Emission from Geminga at 74 and 326 MH[CLC]z[/CLC]

1999 ◽  
Vol 527 (2) ◽  
pp. L101-L104 ◽  
Author(s):  
Namir E. Kassim ◽  
T. Joseph W. Lazio
Keyword(s):  
Continuum Emission ◽  
Upper Limits ◽  
The Continuum

scholarly journals Complex molecular gas kinematics in the inner 5 kpc of 4C12.50 as seen by ALMA

2019 ◽  
Vol 629 ◽  
pp. A30 ◽  
Author(s):  
C. M. Fotopoulou ◽  
K. M. Dasyra ◽  
F. Combes ◽  
P. Salomé ◽  
M. Papachristou
Keyword(s):  
Radio Emission ◽  
Radiation Pressure ◽  
Rotational Velocity ◽  
Molecular Gas ◽  
Signal To Noise ◽  
Active Nucleus ◽  
X Ray ◽  
Gas Kinematics ◽  
Wind Detection ◽  
Co Emission

The nearby system 4C12.50, also known as IRAS 13451+1217 and PKS 1345+12, is a merger of gas-rich galaxies with infrared and radio activity. It has a perturbed interstellar medium (ISM) and a dense configuration of gas and dust around the nucleus. The radio emission at small (∼100 pc) and large (∼100 kpc) scales, as well as the large X-ray cavity in which the system is embedded, are indicative of a jet that could have affected the ISM. We carried out observations of the CO(1−0), (3−2), and (4−3) lines with the Atacama Large Millimeter Array (ALMA) to determine basic properties (i.e., extent, mass, and excitation) of the cold molecular gas in this system, including its already-known wind. The CO emission reveals the presence of gaseous streams related to the merger, which result in a small (∼4 kpc-wide) disk around the western nucleus. The disk reaches a rotational velocity of 200 km s−1, and has a mass of 3.8(±0.4) × 109 M⊙. It is truncated at a gaseous ridge north of the nucleus that is bright in [O III]. Regions with high-velocity CO emission are seen at signal-to-noise ratios of between 3 and 5 along filaments that radially extend from the nucleus to the ridge and that are bright in [O III] and stellar emission. A tentative wind detection is also reported in the nucleus and in the disk. The molecular gas speed could be as high as 2200 km s−1 and the total wind mass could be as high as 1.5(±0.1) × 109 M⊙. Energetically, it is possible that the jet, assisted by the radiation pressure of the active nucleus or the stars, accelerated clouds inside an expanding bubble.

scholarly journals Molecular gas in radio galaxies in dense megaparsec-scale environments at z = 0.4–2.6

2019 ◽  
Vol 623 ◽  
pp. A48 ◽  
Author(s):  
G. Castignani ◽  
F. Combes ◽  
P. Salomé ◽  
C. Benoist ◽  
M. Chiaberge ◽  
...  
Keyword(s):  
Star Formation ◽  
Radio Galaxies ◽  
Stellar Mass ◽  
Gas Content ◽  
Spectral Energy ◽  
Molecular Gas ◽  
Probability Method ◽  
Photometric Redshifts ◽  
Upper Limits ◽  
Co Emission

Context. Low luminosity radio galaxies (LLRGs) typically reside in dense megaparsec-scale environments and are often associated with brightest cluster galaxies (BCGs). They are an excellent tool to study the evolution of molecular gas reservoirs in giant ellipticals, even close to the active galactic nucleus. Aims. We investigate the role of dense megaparsec-scale environment in processing molecular gas in LLRGs in the cores of galaxy (proto-)clusters. To this aim we selected within the COSMOS and DES surveys a sample of five LLRGs at z = 0.4−2.6 that show evidence of ongoing star formation on the basis of their far-infrared (FIR) emission. Methods. We assembled and modeled the FIR-to-UV spectral energy distributions (SEDs) of the five radio sources to characterize their host galaxies in terms of stellar mass and star formation rate. We observed the LLRGs with the IRAM-30 m telescope to search for CO emission. We then searched for dense megaparsec-scale overdensities associated with the LLRGs using photometric redshifts of galaxies and the Poisson Probability Method, which we have upgraded using an approach based on the wavelet-transform (wPPM), to ultimately characterize the overdensity in the projected space and estimate the radio galaxy miscentering. Color-color and color-magnitude plots were then derived for the fiducial cluster members, selected using photometric redshifts. Results. Our IRAM-30 m observations yielded upper limits to the CO emission of the LLRGs, at z = 0.39, 0.61, 0.91, 0.97, and 2.6. For the most distant radio source, COSMOS-FRI 70 at z = 2.6, a hint of CO(7→6) emission is found at 2.2σ. The upper limits found for the molecular gas content M(H2)/M⋆ <  0.11, 0.09, 1.8, 1.5, and 0.29, respectively, and depletion time τdep ≲ (0.2−7) Gyr of the five LLRGs are overall consistent with the corresponding values of main sequence field galaxies. Our SED modeling implies large stellar-mass estimates in the range log(M⋆/M⊙) = 10.9−11.5, typical for giant ellipticals. Both our wPPM analysis and the cross-matching of the LLRGs with existing cluster/group catalogs suggest that the megaparsec-scale overdensities around our LLRGs are rich (≲1014 M⊙) groups and show a complex morphology. The color-color and color-magnitude plots suggest that the LLRGs are consistent with being star forming and on the high-luminosity tail of the red sequence. The present study thus increases the still limited statistics of distant cluster core galaxies with CO observations. Conclusions. The radio galaxies of this work are excellent targets for ALMA as well as next-generation telescopes such as the James Webb Space Telescope.

scholarly journals The ROSAT observations of classical novae

1996 ◽  
Vol 158 ◽  
pp. 289-289
Author(s):  
M. Orio ◽  
H. Ögelman ◽  
S. Balman
Keyword(s):  
Thin Shell ◽  
Black Body ◽  
Archival Data ◽  
X Rays ◽  
Body Temperatures ◽  
Hydrogen Burning ◽  
X Ray ◽  
Classical Novae ◽  
Upper Limits ◽  
The Galaxy

We observed a number of classical and recurrent novae in the Galaxy and the LMC with the ROSAT X-ray telescope and searched the archival data for other serendipitous observations. Preliminary results show that only 9 out of 37 observed objects were bright enough in X-rays to be detected with ROSAT, either in outburst or at quiescence.Three basic mechanisms can cause X-ray emission from classical or re-current novae. The first is hot hydrogen burning in a thin shell of the remnant envelope left on the white dwarf after the nova explosion. Hydrogen burning post-novae should be blackbody like emitters at nearly Eddington luminosity (as per the ‘supersoft’ X-ray sources). In our sample, only GQ Mus (Nova Mus 1983, see Ögelman et al. 1993; Shanley et al. 1995) and V1974 Cyg 1992 (Krautter et al. 1996) had these characteristics. Remarkably, among 10 LMC novae that had an outburst in the last 47 yr none was detected as a ‘supersoft’ X-ray source. The 3 σ upper limits for the black-body temperatures of the post-nova white dwarfs are mainly in the range 20… 30 eV. A post-nova can also emit X-rays because of shocks occurring in the ejected shell (e.g. O’Brien et al. 1994). Three out of four classical novae that were observed in outburst displayed a hard X-ray component in the ROSAT energy band, which might be due to a shocked shell. Finally, X-ray emission is expected from quiescent nearby novae because of accretion. Only four nearby accreting sources were detected; the ROSAT upper limits for the non-detected quiescent novae are Lx < 1031… 1032 ergs−1, assuming a thermal plasma at kT = a few keV.

Angular Distribution and Polarization of the Continuum Emission in Plasmas with Toroidal Symmetry

1988 ◽  
Vol 102 ◽  
pp. 223-225
Author(s):  
M. Lamoureux ◽  
J. Jacquet ◽  
R.H. Pratt
Keyword(s):  
Monte Carlo ◽  
Radiative Recombination ◽  
Distribution Functions ◽  
Tokamak Plasma ◽  
Degree Of Polarization ◽  
Continuum Emission ◽  
Monte Carlo Code ◽  
Superthermal Electrons ◽  
X Ray ◽  
The Continuum

AbstractSuperthermal electrons in plasmas are usually strongly directional, and this confers angular dependence and polarization to the X-ray continuum radiation emitted. Here, we give the relations between the anisotropic distribution functions f(v,θ) and the degree of polarization of the emission due to direct radiative recombination and bremsstrahlung. An application is then made to a tokamak plasma whose f(v,θ) we obtained from a Monte Carlo code.

scholarly journals Probing the magnetospheric accretion region of the young pre-transitional disk system DoAr 44 using VLTI/GRAVITY

2020 ◽  
Vol 636 ◽  
pp. A108 ◽  
Author(s):  
J. Bouvier ◽  
K. Perraut ◽  
J.-B. Le Bouquin ◽  
G. Duvert ◽  
C. Dougados ◽  
...  
Keyword(s):  
Geometric Model ◽  
Stellar System ◽  
Line Emission ◽  
Position Angle ◽  
Young Stellar Objects ◽  
Continuum Emission ◽  
Disk System ◽  
Compact Region ◽  
Magnetospheric Accretion ◽  
The Continuum

Context. Young stellar objects are thought to accrete material from their circumstellar disks through their strong stellar magnetospheres. Aims. We aim to directly probe the magnetospheric accretion region on a scale of a few 0.01 au in a young stellar system using long-baseline optical interferometry. Methods. We observed the pre-transitional disk system DoAr 44 with VLTI/GRAVITY on two consecutive nights in the K-band. We computed interferometric visibilities and phases in the continuum and in the Brγ line in order to constrain the extent and geometry of the emitting regions. Results. We resolve the continuum emission of the inner dusty disk and measure a half-flux radius of 0.14 au. We derive the inclination and position angle of the inner disk, which provides direct evidence that the inner and outer disks are misaligned in this pre-transitional system. This may account for the shadows previously detected in the outer disk. We show that Brγ emission arises from an even more compact region than the inner disk, with an upper limit of 0.047 au (~5 R⋆). Differential phase measurements between the Brγ line and the continuum allow us to measure the astrometric displacement of the Brγ line-emitting region relative to the continuum on a scale of a few tens of microarcsec, corresponding to a fraction of the stellar radius. Conclusions. Our results can be accounted for by a simple geometric model where the Brγ line emission arises from a compact region interior to the inner disk edge, on a scale of a few stellar radii, fully consistent with the concept of magnetospheric accretion process in low-mass young stellar systems.

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