- ID:
- ivo://CDS.VizieR/J/A+A/641/A151
- Title:
- NGC 7213 central region molecular gas
- Short Name:
- J/A+A/641/A151
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a multi-wavelength study (from X-ray to mm) of the nearby low-luminosity active galactic nucleus (LLAGN) NGC 7213. We combine the information from the different bands to characterise the source in terms of contribution from the AGN and the host-galaxy interstellar medium (ISM). This approach allows us to provide a coherent picture of the role of the AGN and its impact, if any, on the star formation and molecular gas properties of the host galaxy. We focused our study on archival ALMA Cycle 1 observations, where the CO(2-1) emission line has been used as a tracer of the molecular gas. Using the 3DBarolo code on ALMA data, we performed the modelling of the molecular gas kinematics traced by the CO(2-1) emission, finding a rotationally dominated pattern. The molecular gas mass of the host galaxy was estimated from the integrated CO(2-1) emission line obtained with APEX data, assuming an alpha_co conversion factor. Had we used the ALMA data, we would have underestimated the gas masses by a factor ~3, given the filtering out of the large-scale emission in interferometric observations. We also performed a complete X-ray spectral analysis on archival observations, revealing a relatively faint and unobscured AGN. The AGN proved to be too faint to significantly affect the properties of the host galaxy, such as star formation activity and molecular gas kinematics and distribution.
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- ID:
- ivo://CDS.VizieR/J/A+A/613/A3
- Title:
- NGC 1068 deep millimeter spectroscopy observations
- Short Name:
- J/A+A/613/A3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We aim for a better understanding of gas properties in the circum-nuclear disk (CND) region of the nearby gas-rich Seyfert 2 galaxy NGC 1068. We focus on line identification and the basic physical parameters estimation of molecular gas in the CND region. Methods. We used the IRAM 30m telescope to conduct deep millimeter spectroscopy observations toward the center of NGC 1068.
- ID:
- ivo://CDS.VizieR/J/A+A/602/A78
- Title:
- NGC1068 interferometric mid-IR measurements
- Short Name:
- J/A+A/602/A78
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent NuSTAR observations revealed a somewhat unexpected increase in the X-ray flux of the nucleus of NGC 1068. We expect the infrared emission of the dusty torus to react on the intrinsic changes of the accretion disk. We aim to investigate the origin of the X-ray variation by investigating the response of the mid-infrared environment. We obtained single-aperture and interferometric mid-infrared measurements and directly compared the measurements observed before and immediately after the X-ray variations. The average correlated and single-aperture fluxes as well as the differential phases were directly compared to detect a possible change in the structure of the nuclear emission on scales of ~2pc. The flux densities and differential phases of the observations before and during the X-ray variation show no significant change over a period of ten years. Possible minor variations in the infrared emission are ~6%. Our results suggest that the mid-infrared environment of NGC 1068 has remained unchanged for a decade. The recent transient change in the X-rays did not cause a significant variation in the infrared emission. This independent study supports previous conclusions that stated that the X-ray variation detected by NuSTAR observations is due to X-ray emission piercing through a patchy section of the dusty region.
534. NGC4395 light curves
- ID:
- ivo://CDS.VizieR/J/ApJ/632/799
- Title:
- NGC4395 light curves
- Short Name:
- J/ApJ/632/799
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A reverberation-mapping program on NGC 4395, the least luminous known Seyfert 1 galaxy, undertaken with the Space Telescope Imaging Spectrograph on the Hubble Space Telescope yields a measurement of the mass of the central black hole M_BH_=(3.6+/-1.1)x10^5^M_{sun}_. The observations consist of two visits of five orbits each, in 2004 April and July. During each of these visits, the UV continuum varied by at least 10% (rms), and only C IV {lambda}1549 showed corresponding variations large enough to reliably determine the emission-line lag, which was measured to be of order 1-hr for both visits.
- ID:
- ivo://CDS.VizieR/J/ApJ/650/88
- Title:
- NGC4395 light curves. III.
- Short Name:
- J/ApJ/650/88
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present optical observations of the low-luminosity Seyfert 1 nucleus of NGC 4395, as part of a multiwavelength reverberation-mapping program. Observations were carried out over two nights in 2004 April at Lick, Wise, and Kitt Peak Observatories. We obtained V- and B-band photometry, and spectra over the range 3500-6800{AA}. Simultaneous Hubble Space Telescope UV and Chandra X-ray observations are presented in companion papers.
- ID:
- ivo://CDS.VizieR/J/A+A/565/A71
- Title:
- NGC1068 MIDI/VLTI observations
- Short Name:
- J/A+A/565/A71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The aim of this paper is to understand the relation in active galactic nuclei (AGNs) between the small obscuring torus and dusty structures at larger scales (5-10pc). The dusty structures in AGNs are best observed in the mid-infrared. To achieve the necessary spatial resolution (20-100 milliarcsec) we use ESO's Mid-Infrared Interferometer (MIDI) with the 1.8m Auxiliary Telescopes. We use the chromatic phases in the data to improve the spatial fidelity of the analysis.
- ID:
- ivo://CDS.VizieR/J/A+A/633/A79
- Title:
- NGC 6240 MUSE observations
- Short Name:
- J/A+A/633/A79
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 6240 is a well-studied nearby galaxy system in the process of merging. Based on optical, X-ray, and radio observations, it is thought to harbor two active nuclei. We carried out a detailed optical 3D spectroscopic study to investigate the inner region of this system in connection with existing MERLIN and VLBA data. We observed NGC 6240 with very high spatial resolution using the MUSE instrument in the Narrow-Field Mode with the four-laser GALACSI adaptive optics system on the ESO VLT under seeing conditions of 0.49''. Our 3D spectra cover the wavelength range from 4725 to 9350 Angstroem at a spatial resolution of about 75 mas. We report the discovery of three nuclei in the final state of merging within a region of only 1 kpc in the NGC 6240 system. Thanks to MUSE we are able to show that the formerly unresolved southern component actually consists of two distinct nuclei separated by only 198pc. In combination with Gaia data we reach an absolute positional accuracy of only 30mas that is essential to compare optical spectra with MERLIN and VLBA radio positions. The verification and detailed study of a system with three nuclei, two of which are active and each with a mass in excess of 9x10^7^M_{sun}_, is of great importance for the understanding of hierarchical galaxy formation via merging processes since multiple mergers lead to a faster evolution of massive galaxies in comparison to binary mergers. So far it has been suggested that the formation of galactic nuclei with multiple supermassive black holes (SMBHs) is expected to be rare in the local universe. Triple massive black hole systems might be of fundamental importance for the coalescence of massive black hole binaries in less than a Hubble time leading to the loudest sources of gravitational waves in the megahertz regime.
- ID:
- ivo://CDS.VizieR/J/A+A/634/A125
- Title:
- NGC 1068 nucleus molecular line spectra at 2mm
- Short Name:
- J/A+A/634/A125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the physical and chemical conditions of molecular gas in the circumnuclear disk (CND) region of NGC 1068. We carried out a spectral line survey with the IRAM 30m telescope toward the center of NGC 1068 and mainly focused on the 2mm band with a frequency coverage of 160.7-168.6GHz and 176.5-184.3GHz. Fifteen lines are detected in NGC 1068, eight of which are new detections for this galaxy. We derive the rotation temperatures and column densities of fourteen molecular species. Based on the [HCO^+^ (2-1)]/[HOC^+^ (2-1)] ratio, we obtain a high ionization degree in the CND of NGC 1068. It is found that HC_3_N is concentrated in the east knot, while ^13^CCH, CH_3_CN, SO, HOC^+^, CS, CH_3_CCH, and H_2_CO are concentrated in the west knot. Compared to the star-forming galaxies M 82 and NGC 253, the chemistry of NGC 1068 might be less strongly affected by the UV radiation field, and its kinetic temperature might be lower.
- ID:
- ivo://CDS.VizieR/J/A+A/638/A13
- Title:
- NGC 3516 optical flare
- Short Name:
- J/A+A/638/A13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present observations from the short-term intensive optical campaign (from September 2019 to January 2020) of the changing-look Seyfert NGC 3516. This active galactic nucleus is known to have strong optical variability and has changed its type in the past. It has been in the low-activity state in the optical since 2013, with some rebrightening from the end of 2015 to the beginning of 2016, after which it remained dormant. We aim to study the photometric and spectral variability of NGC 3516 from the new observations in U- and B-bands and examine the profiles of the optical broad emission lines in order to demonstrate that this object may be entering a new state of activity. NGC 3516 has been monitored intensively for the past 4 months with an automated telescope in U and B filters, enabling accurate photometry of 0.01 precision. Spectral observations were triggered when an increase in brightness was spotted. We support our analysis of past-episodes of violent variability with the UV and X-ray long-term light curves constructed from the archival Swift/UVOT and Swift/XRT data. An increase of the photometric magnitude is seen in both U and B filters to a maximum amplitude of 0.25mag and 0.11mag, respectively. During the flare, we observe stronger forbidden high-ionization iron lines ([FeVII] and [FeX]) than reported before, as well as the complex broad H{alpha} and H{beta} lines. This is especially seen in H{alpha}, which appears to be double-peaked. It seems that a very broad component of ~10000km/s in width in the Balmer lines is appearing. The trends in the optical, UV, and X-ray light curves are similar, with the amplitudes of variability being significantly larger in the case of UV and X-ray bands. The increase of the continuum emission, the variability of the coronal lines, and the very broad component in the Balmer lines may indicate that the AGN of NGC 3516 is finally leaving the low-activity state in which it has been for the last ~3 years.
- ID:
- ivo://CDS.VizieR/J/A+A/623/A27
- Title:
- NGC1052 twin-jet VLBI images
- Short Name:
- J/A+A/623/A27
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Few active galactic nuclei (AGN) reveal double-sided jet systems. However, these systems are crucial to understand basic physical properties of extragalactic jets. We address the questions whether jets in AGN are symmetric in nature, how well they are collimated on small scales, and how they evolve with time. We monitored the sub-parsec scale morphology of NGC 1052 with the Very Long Baseline Array at 43GHz from 2005 to 2009. A detailed study of 29 epochs show a remarkable asymmetry between both jets. A kinematic analysis of the outflows reveals higher apparent velocities for the eastern (approaching) jet as compared to the western (receding) jet, i.e., {beta}_ej_=0.529+/-0.038 and {beta}_wj_=0.343+/-0.037, respectively. Contradictory to previous studies, we find higher flux densities for the western jet as compared to the eastern. The distribution of brightness temperature and jet width features well-collimated jets up to 1 mas distance to the dynamic center and a nearly conical outflow further outward. By combining flux density ratios and velocities of the jet flows, we were unable to find a combination of intrinsic velocities and inclination angles of the jets that is consistent for all four years of observation; this contradicts findings for symmetrically evolving jets. Spectral index maps between quasi-simultaneous 22GHz and 43GHz observations support the existence of an optically thick absorber covering the innermost ~=1.6mas around the 43GHz central feature and an optically thin jet emission with a spectral index of <=-1. Our results fit into a picture in which we expect larger internal energy and/or magnetic flux in the western jet and higher kinetic energy in the eastern jet. Previous observations at lower frequencies have found slower velocities of the moving jet features as compared to this work. Considering the different velocities in different areas, we suggest a spine-sheath structure with a faster inner layer and slower outer layer.
