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531. New 2.2<z<3 quasars from SDSS and UKIDSS
ID:
ivo://CDS.VizieR/J/AJ/142/78
Title:
New 2.2<z<3 quasars from SDSS and UKIDSS
Short Name:
J/AJ/142/78
Date:
21 Oct 2021
Publisher:
CDS
Description:
The identification of quasars in the redshift range 2.2<z<3 is known to be very inefficient because the optical colors of such quasars are indistinguishable from those of stars. Recent studies have proposed using optical variability or near-infrared (near-IR) colors to improve the identification of the missing quasars in this redshift range. Here we present a case study combining both methods. We select a sample of 70 quasar candidates from variables in Sloan Digital Sky Survey (SDSS) Stripe 82, which are non-ultraviolet excess sources and have UKIDSS near-IR public data. They are clearly separated into two parts on the Y-K/g-z color-color diagram, and 59 of them meet or lie close to a newly proposed Y-K/g-z selection criterion for z<4 quasars. Of these 59 sources, 44 were previously identified as quasars in SDSS DR7, and 35 of them are quasars at 2.2<z<3. We present spectroscopic observations of 14 of 15 remaining quasar candidates using the Bok 2.3m telescope and the MMT 6.5m telescope, and successfully identify all of them as new quasars at z=2.36-2.88. We also apply this method to a sample of 643 variable quasar candidates with SDSS-UKIDSS nine-band photometric data selected from 1875 new quasar candidates in SDSS Stripe 82 given by Butler & Bloom (2011AJ....141...93B) based on the time-series selections, and find that 188 of them are probably new quasars with photometric redshifts at 2.2<z<3. Our results indicate that the combination of optical variability and optical/near-IR colors is probably the most efficient way to find 2.2<z<3 quasars and is very helpful for constructing a complete quasar sample. We discuss its implications for ongoing and upcoming large optical and near-IR sky surveys.
532. NGC 1377 ALMA CO 3-2 and 0.8mm continuum images
ID:
ivo://CDS.VizieR/J/A+A/640/A104
Title:
NGC 1377 ALMA CO 3-2 and 0.8mm continuum images
Short Name:
J/A+A/640/A104
Date:
21 Oct 2021
Publisher:
CDS
Description:
Submillimetre and millimetre line and continuum observations are important in probing the morphology, column density, and dynamics of the molecular gas and dust around obscured active galactic nuclei (AGNs) and their mechanical feedback. With very high resolution (0.02"x0.03" (2x3pc)) ALMA 345GHz observations of CO 3-2, HCO^+^ 4-3, vibrationally excited HCN 4-3 {nu}_2_=1f , and continuum we have studied the remarkable, extremely radio-quiet, molecular jet and wind of the lenticular galaxy NGC 1377. The outflow structure is resolved, revealing a 150pc long, clumpy, high-velocity (600km/s), collimated molecular jet where the molecular emission is emerging from the spine of the jet with an average diameter of 3-7pc. The jet widens to 10-15pc about 25pc from the centre, which is possibly due to jet-wind interactions. A narrow-angle (50-70), misaligned and rotating molecular wind surrounds the jet, and both are enveloped by a larger-scale CO-emitting structure at near-systemic velocity. The jet and narrow wind have steep radial gas excitation gradients and appear turbulent with high gas dispersion (>40km/s). The jet shows velocity reversals that we propose are caused by precession, or more episodic directional changes. We discuss the mechanisms powering the outflow, and we find that an important process for the molecular jet and narrow wind is likely magneto-centrifugal driving. In contrast, the large-scale CO-envelope may be a slow wind, or cocoon that stems from jet-wind interactions. An asymmetric, nuclear r~2pc dust structure with a high inferred molecular column density N(H_2_)=1.8x10^24^cm^-2^ is detected in continuum and also shows compact emission from vibrationally excited HCN. The nuclear dust emission is hot (Td>180K) and its luminosity is likely powered by a buried AGN. The lopsided structure appears to be a warped disk, which is responsible for a significant part of the nuclear obscuration and possibly formed as a result of uneven gas inflows. The dynamical mass inside r=1.4pc is estimated to 9^+2^_3_x10^6^M_{sun}_, implying that the supermassive black hole (SMBH) has a high mass with respect to the stellar velocity dispersion of NGC 1377. We suggest that the SMBH of NGC 1377 is currently in a state of moderate growth, at the end of a more intense phase of accretion and also evolving from a state of more extreme nuclear obscuration. The nuclear growth may be fuelled by low-angular momentum gas inflowing from the gas ejected in the molecular jet and wind. Such a feedback-loop of cyclic outflows and central accretion could explain why there is still a significant reservoir of molecular gas in this ageing, lenticular galaxy. A feedback-loop would be an effective process in growing the nuclear SMBH and thus would constitute an important phase in the evolution of NGC 1377. This also invites new questions as to SMBH growth processes in obscured, dusty galaxies.
533. NGC 613 ALMA datacubes
ID:
ivo://CDS.VizieR/J/A+A/632/A33
Title:
NGC 613 ALMA datacubes
Short Name:
J/A+A/632/A33
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report ALMA observations of CO(3-2) emission in the Seyfert/nuclear starburst galaxy NGC613, at a spatial resolution of 17pc, as part of our NUclei of GAlaxies (NUGA) sample. Our aim is to investigate the morphology and dynamics of the gas inside the central kiloparsec, and to probe nuclear fueling and feedback phenomena. The morphology of CO(3-2) line emission reveals a two arm trailing nuclear spiral at r<~100pc and a circumnuclear ring at a radius of ~350pc that is coincident with the star-forming ring seen in the optical images. Also, we find evidence for a filamentary structure connecting the ring and the nuclear spiral. The ring reveals two breaks into two winding spiral arms corresponding to the dust lanes in the optical images. The molecular gas in the galaxy disk is in a remarkably regular rotation, however the kinematics in the nuclear region are very skewed. The nuclear spectrum of CO and dense gas tracers HCN(4-3), HCO^+^(4-3), and CS(7-6) show broad wings up to 300km/s, associated with a molecular outflow emanating from the nucleus (r~25pc). We derive a molecular outflow mass M_out_=2x10^6^M_[sun}_ and a mass outflow rate of dM_out_/dt=27M_[sun}/yr. The molecular outflow energetics exceed the values predicted by AGN feedback models: the kinetic power of the outflow corresponds to P_K,out_=20%L_AGN_ and the momentum rate is dM_out_/dt*v~400L_AGN_/c. The outflow is mainly boosted by the AGN through entrainment by the radio jet, but given the weak nuclear activity of NGC613, we might be witnessing a fossil outflow resulting from a previously strong AGN that has now faded. Furthermore, the nuclear trailing spiral observed in CO emission is inside the inner Lindblad resonance ring of the bar. We compute the gravitational torques exerted in the gas to estimate the efficiency of the angular momentum exchange. The gravity torques are negative from 25 to 100pc and the gas loses its angular momentum in a rotation period, providing evidence for a highly efficient inflow towards the center. This phenomenon shows that the massive central black hole has significant dynamical influence on the gas, triggering the inflowing of molecular gas to feed the black hole.
534. NGC 7213 central region molecular gas
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.
535. NGC 1068 deep millimeter spectroscopy observations
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.
536. NGC1068 interferometric mid-IR measurements
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.
537. 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.
538. NGC4395 light curves. III.
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.
539. NGC1068 MIDI/VLTI observations
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.
540. NGC 6240 MUSE observations
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.