- ID:
- ivo://CDS.VizieR/J/A+A/643/A127
- Title:
- 5 Seyferts reduced CO(2-1) cubes
- Short Name:
- J/A+A/643/A127
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Active galactic nucleus (AGN) driven outflows are believed to play an important role in regulating the growth of galaxies, mostly via negative feedback. However, their effects on their hosts are far from clear, especially for low- and moderate-luminosity Seyferts. To investigate this issue, we obtained cold molecular gas observations, traced by the CO(2-1) transition, using the NOEMA interferometer of five nearby (distances between 19 and 58Mpc) Seyfert galaxies. The resolution of ~0.3-0.8 (~30-100pc) and field of view of NOEMA allowed us to study the CO(2-1) morphology and kinematics in the nuclear regions (~100pc) and up to radial distances of ~900pc. We detected CO(2-1) emission in all five galaxies with disky or circumnuclear ring-like morphologies. We derived cold molecular gas masses on nuclear (~100pc) and circumnuclear (~650pc) scales in the range from 10^6^ to 10^7^M_{sun}_ and from 10^7^ to 10^8^M_{sun}_, respectively. In all of our galaxies, the bulk of this gas is rotating in the plane of the galaxy. However, noncircular motions are also present. In NGC 4253, NGC 4388, and NGC 7465, we can ascribe the streaming motions to the presence of a large-scale bar. In Mrk 1066 and NGC 4388, the noncircular motions in the nuclear regions are explained as outflowing material due to the interaction of the AGN wind with molecular gas in the galaxy disk. We conclude that for an unambiguous and precise interpretation of the kinematics of the cold molecular gas, we need detailed knowledge of the host galaxy (i.e., presence of bars, interactions, etc.), and also of the ionized gas kinematics and ionization cone geometry.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/621/A119
- Title:
- SgrA* and NRAS530 86GHz images
- Short Name:
- J/A+A/621/A119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The compact radio source Sagittarius A* (Sgr A*) in the Galactic centre is the primary supermassive black hole candidate. General relativistic magnetohydrodynamical (GRMHD) simulations of the accretion flow around Sgr A* predict the presence of sub-structure at observing wavelengths of ~3mm and below (frequencies of 86GHz and above). For very long baseline interferometry (VLBI) observations of Sgr A* at this frequency the blurring effect of interstellar scattering becomes sub-dominant, and arrays such as the high sensitivity array (HSA) and the global mm-VLBI array (GMVA) are now capable of resolving potential sub-structure in the source. Such investigations help to improve our understanding of the emission geometry of the mm-wave emission of Sgr A*, which is crucial for constraining theoretical models and for providing a background to interpret 1mm VLBI data from the Event Horizon Telescope (EHT). Following the closure phase analysis in our first paper, which indicates asymmetry in the 3 mm emission of Sgr A*, here we have used the full visibility information to check for possible sub-structure. We extracted source size information from closure amplitude analysis, and investigate how this constrains a combined fit of the size-frequency relation and the scattering law for Sgr A*. We performed high-sensitivity VLBI observations of Sgr A* at 3mm using the Very Long Baseline Array (VLBA) and the Large Millimeter Telescope (LMT) in Mexico on two consecutive days in May 2015, with the second epoch including the Greenbank Telescope (GBT). We confirm the asymmetry for the experiment including GBT. Modelling the emission with an elliptical Gaussian results in significant residual flux of ~10mJy in south-eastern direction. The analysis of closure amplitudes allows us to precisely constrain the major and minor axis size of the main emission component. We discuss systematic effects which need to be taken into account. We consider our results in the context of the existing body of size measurements over a range of observing frequencies and investigate how well-constrained the size-frequency relation is by performing a simultaneous fit to the scattering law and the size-frequency relation. We find an overall source geometry that matches previous findings very closely, showing a deviation in fitted model parameters less than 3% over a time scale of weeks and suggesting a highly stable global source geometry over time. The reported sub-structure in the 3mm emission of Sgr A* is consistent with theoretical expectations of refractive noise on long baselines. However, comparing our findings with recent results from 1mm and 7mm VLBI observations, which also show evidence for east-west asymmetry, we cannot exclude an intrinsic origin. Confirmation of persistent intrinsic substructure will require further VLBI observations spread out over multiple epochs.
- ID:
- ivo://CDS.VizieR/J/other/Sci/348.413
- Title:
- Sgr A East SNR multiwavelength images
- Short Name:
- J/other/Sci/348.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Dust formation in supernova ejecta is currently the leading candidate to explain the large quantities of dust observed in the distant, early universe. However, it is unclear whether the ejecta-formed dust can survive the hot interior of the supernova remnant (SNR). We present infrared observations of ~0.02 solar masses of warm (~100 kelvin) dust seen near the center of the ~10,000-year-old Sagittarius A East SNR at the Galactic center. Our findings indicate the detection of dust within an older SNR that is expanding into a relatively dense surrounding medium (electron density ~10^3^ centimeters^-3^) and has survived the passage of the reverse shock. The results suggest that supernovae may be the dominant dust-production mechanism in the dense environment of galaxies of the early universe.
1544. SgrA* emission at 7mm
- ID:
- ivo://CDS.VizieR/J/MNRAS/428/2731
- Title:
- SgrA* emission at 7mm
- Short Name:
- J/MNRAS/428/2731
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the result of 6yr monitoring of SgrA*, radio source associated with the supermassive black hole at the centre of the Milky Way. Single dish observations were performed with the Itapetinga radio telescope at 7mm, and the contribution of the SgrA Complex that surrounds SgrA* was subtracted and used as instantaneous calibrator. The observations were alternated every 10-min with those of the HII region SrgB2, which was also used as a calibrator. The reliability of the detections was tested comparing them with simultaneous observations using interferometric techniques. During the observing period we detected a continuous increase in the SgrA* flux density starting in 2008, as well as variability in time-scales of days and strong intraday fluctuations.
- ID:
- ivo://CDS.VizieR/J/A+A/618/L10
- Title:
- SgrA* orbital motions with GRAVITY
- Short Name:
- J/A+A/618/L10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the detection of continuous positional and polarization changes of the compact source SgrA* in high states ('flares') of its variable near- infrared emission with the near-infrared GRAVITY-Very Large Telescope Interferometer (VLTI) beam-combining instrument. In three prominent bright flares, the position centroids exhibit clockwise looped motion on the sky, on scales of typically 150 micro-arcseconds over a few tens of minutes, corresponding to about 30% the speed of light. At the same time, the flares exhibit continuous rotation of the polarization angle, with about the same 45(+/-15)-minute period as that of the centroid motions. Modelling with relativistic ray tracing shows that these findings are all consistent with a near face-on, circular orbit of a compact polarized 'hot spot' of infrared synchrotron emission at approximately six to ten times the gravitational radius of a black hole of 4 million solar masses. This corresponds to the region just outside the innermost, stable, prograde circular orbit (ISCO) of a Schwarzschild-Kerr black hole, or near the retrograde ISCO of a highly spun-up Kerr hole. The polarization signature is consistent with orbital motion in a strong poloidal magnetic field.
- ID:
- ivo://CDS.VizieR/J/AJ/127/3399
- Title:
- Sgr A* variability at cm wavelengths
- Short Name:
- J/AJ/127/3399
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a 3.3yr project to monitor the flux density of Sagittarius A* at 2.0, 1.3, and 0.7cm with the Very Large Array. Between 2000.5 and 2003.0, 119 epochs of data were taken with a mean separation between epochs of 8 days. After 2003.0, observations were made roughly once per month for a total of nine additional epochs. Details of the data calibration process are discussed, including corrections for opacity and elevation effects, as well as changes in the flux density scales between epochs. The fully calibrated light curves for Sgr A* at all three wavelengths are presented.
- ID:
- ivo://CDS.VizieR/J/A+A/604/A6
- Title:
- SgrB2 ALMA continuum and spectral index
- Short Name:
- J/A+A/604/A6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The two hot molecular cores SgrB2(M) and SgrB2(N), which are located at the center of the giant molecular cloud complex Sagittarius B2, have been the targets of numerous spectral line surveys, revealing a rich and complex chemistry. We seek to characterize the physical and chemical structure of the two high-mass star-forming sites SgrB2(M) and SgrB2(N) using high-angular resolution observations at millimeter wavelengths, reaching spatial scales of about 4000au. We used the Atacama Large Millimeter/submillimeter Array (ALMA) to perform an unbiased spectral line survey of both regions in the ALMA band 6 with a frequency coverage from 211GHz to 275GHz. The achieved angular resolution is 0.4-arcsec, which probes spatial scales of about 4000au, i.e., able to resolve different cores and fragments. In order to determine the continuum emission in these line-rich sources, we used a new statistical method, STATCONT, which has been applied successfully to this and other ALMA datasets and to synthetic observations. We detect 27 continuum sources in SgrB2(M) and 20 sources in SgrB2(N). We study the continuum emission variation across the ALMA band 6 (i.e., spectral index) and compare the ALMA 1.3mm continuum emission with previous SMA 345GHz and VLA 40GHz observations to study the nature of the sources detected. The brightest sources are dominated by (partially optically thick) dust emission, while there is an important degree of contamination from ionized gas free-free emission in weaker sources. While the total mass in SgrB2(M) is distributed in many fragments, most of the mass in SgrB2(N) arises from a single object, with filamentary-like structures converging toward the center. There seems to be a lack of low-mass dense cores in both regions. We determine H2 volume densities for the cores of about 10^7^-10^9^cm^-3^ (or 10^5^-10^7^M_{sun}_/pc^3^), i.e., one to two orders of magnitude higher than the stellar densities of super star clusters. We perform a statistical study of the chemical content of the identified sources. In general, SgrB2(N) is chemically richer than SgrB2(M). The chemically richest sources have about 100 lines per GHz and the fraction of luminosity contained in spectral lines at millimeter wavelengths with respect to the total luminosity is about 20%-40%. There seems to be a correlation between the chemical richness and the mass of the fragments, where more massive clumps are more chemically rich. Both SgrB2(N) and SgrB2(M) harbor a cluster of hot molecular cores. We compare the continuum images with predictions from a detailed 3D radiative transfer model that reproduces the structure of SgrB2 from 45pc down to 100au. This ALMA dataset, together with other ongoing observational projects in the range 5GHz to 200GHz, better constrain the 3D structure of SgrB2 and allow us to understand its physical and chemical structure.
1548. Sgr B2 spectral survey
- ID:
- ivo://CDS.VizieR/J/ApJS/117/427
- Title:
- Sgr B2 spectral survey
- Short Name:
- J/ApJS/117/427
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have surveyed the frequency band 218.30-263.55GHz toward the core positions N and M and the quiescent cloud position NW in the Sgr B2 molecular cloud using the Swedish-ESO Submillimetre Telescope. In total 1730, 660, and 110 lines were detected in N, M, and NW, respectively, and 42 different molecular species were identified. The number of unidentified lines are 337, 51, and eight. Toward the N source, spectral line emission constitutes 22% of the total detected flux in the observed band, and complex organic molecules are the main contributors. Toward M, 14% of the broadband flux is caused by lines, and SO2 is here the dominant source of emission. NW is relatively poor in spectral lines and continuum. In this paper we present the spectra together with tables of suggested line identifications.
- ID:
- ivo://CDS.VizieR/J/A+A/641/A40
- Title:
- S5 0836+710 Ground and Space VLBI images
- Short Name:
- J/A+A/641/A40
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Detailed studies of relativistic jets in active galactic nuclei (AGN) require high-fidelity imaging at the highest possible resolution. This can be achieved using very long baseline interferometry (VLBI) at radio frequencies, combining worldwide (global) VLBI arrays of radio telescopes with a space-borne antenna on board a satellite. We present multiwavelength images made of the radio emission in the powerful quasar S5 0836+710, obtained using a global VLBI array and the antenna Spektr-R of the RadioAstron mission of the Russian Space Agency, with the goal of studying the internal structure and physics of the relativistic jet in this object. The RadioAstron observations at wavelengths of 18cm, 6cm, and 1.3cm are part of the Key Science Program for imaging radio emission in strong AGN. The internal structure of the jet is studied by analyzing transverse intensity profiles and modeling the structural patterns developing in the flow. The RadioAstron images reveal a wealth of structural detail in the jet of S5 0836+710 on angular scales ranging from 0.02mas to 200mas. Brightness temperatures in excess of 10^13^K are measured in the jet, requiring Doppler factors of >=100 for reconciling them with the inverse Compton limit. Several oscillatory patterns are identified in the ridge line of the jet and can be explained in terms of the Kelvin-Helmholtz (KH) instability. The oscillatory patterns are interpreted as the surface and body wavelengths of the helical mode of the KH instability. The interpretation provides estimates of the jet Mach number and of the ratio of the jet to the ambient density, which are found to be Mj~=12 and {eta}~=0.33. The ratio of the jet to the ambient density should be conservatively considered an upper limit because its estimate relies on approximations.
- ID:
- ivo://CDS.VizieR/J/A+AS/114/21
- Title:
- Shapley-Ames Galaxies at 2.8cm
- Short Name:
- J/A+AS/114/21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present measurements of the radio continuum emission at 2.8 cm of a nearly complete sample of spiral galaxies. The sample consists of the Shapley-Ames galaxies north of {delta}=-25deg and brighter than B_T_=+12. The large, nearby galaxies were not observed during the survey, but measured with high sensitivity in individual projects. The radioweak galaxies were also excluded. The observational results and the derived flux densities are given and compared with that of other observations. Pecularities of the radio emission of individual galaxies are discussed.