ABSTRACT
We employ MUSE/VLT data to study the ionized and highly ionized gas phases of the feedback in Circinus, the closest Seyfert 2 galaxy to us. The analysis of the nebular emission allowed us to ...detect a remarkable high-ionization gas outflow beyond the galaxy plane traced by the coronal lines Fe vii λ6089 and Fe x λ6374, extending up to 700 and 350 pc NW from the nucleus, respectively. This is the first time that the Fe x emission is observed at such distances from the central engine in an active galactic nucleus (AGN). The gas kinematics reveals expanding gas shells with velocities of a few hundred km s−1, spatially coincident with prominent hard X-ray emission detected by Chandra. Density and temperature sensitive line ratios show that the extended high-ionization gas is characterized by a temperature reaching 25 000 K and an electron density >102 cm−3. We found that local gas excitation by shocks produced by the passage of a radio jet leads to the spectacular high-ionization emission in this object. This hypothesis is fully supported by photoionization models that account for the combined effects of the central engine and shocks. They reproduce the observed emission line spectrum at different locations inside and outside of the NW ionization cone. The energetic outflow produced by the radio jet is spatially located close to an extended molecular outflow recently reported using ALMA which suggests that they both represent different phases of the same feedback process acting on the AGN.
Abstract We recently built the G4Jy-3CRE catalog of extragalactic radio sources. This catalog lists 264 powerful radio sources selected with similar criteria to those of the revised Third Cambridge ...Catalog, but visible from the Southern Hemisphere. A literature search revealed that 119 sources in the G4Jy-3CRE catalog (i.e., 45%) lack a firm spectroscopic redshift measurement. Here, we present a campaign aimed at acquiring optical spectra of G4Jy-3CRE sources and measuring their redshifts. We used single-slit observations obtained with the Víctor Blanco Telescope, the New Technology Telescope, the Southern Astrophysical Research Telescope, and the 2.1 m telescope of the Observatorio Astronómico Nacional at San Pedro Mártir, Mexico. In addition, we analyzed Very Large Telescope/MUSE archival observations. From these observations, we report the spectra and redshifts of 93 sources, 42 of which are the first optical spectra and redshift determinations for the respective sources. With our new data, approximately 71% of the sources in the G4Jy-3CRE catalog now have firm spectroscopic redshift measurements. This data set will be the basis of our future analysis of the optical properties of the G4Jy-3CRE catalog.
Abstract
We recently constructed the G4Jy-3CRE, a catalog of extragalactic radio sources based on the GLEAM 4-Jy (G4Jy) sample, with the aim of increasing the number of powerful radio galaxies and ...quasars with similar selection criteria to those of the revised release of the Third Cambridge Catalog (3CR). The G4Jy-3CRE consists of a total of 264 radio sources mainly visible from the Southern Hemisphere. Here, we present an initial X-ray analysis of 89 G4Jy-3CRE radio sources with archival X-ray observations from the Neil Gehrels Swift Observatory. We reduced a total of 624 Swift observations, for about 0.9 Ms of integrated exposure time. We found X-ray counterparts for 59 radio sources belonging to the G4Jy-3CRE, nine of them showing extended X-ray emission. The remaining 30 sources do not show any X-ray emission associated with their radio cores. Our analysis demonstrates that X-ray snapshot observations, even if lacking uniform exposure times, as those carried out with Swift, allow us to (i) verify and/or refine the host galaxy identification; (ii) discover the extended X-ray emission around radio galaxies of the intracluster medium when harbored in galaxy clusters, as the case of G4Jy 1518 and G4Jy 1664; and (iii) detect X-ray radiation arising from their radio lobes, as for G4Jy 1863.
Abstract
Since the early sixties, our view of radio galaxies and quasars has been drastically shaped by discoveries made thanks to observations of radio sources listed in the Third Cambridge Catalog ...and its revised version (3CR). However, the largest fraction of data collected to date on 3CR sources was performed with relatively old instruments, rarely repeated and/or updated. Importantly, the 3CR contains only objects located in the Northern Hemisphere, thus having limited access to new and innovative astronomical facilities. To mitigate these limitations, we present a new catalog of powerful radio sources visible from the Southern Hemisphere, extracted from the GLEAM 4 Jy (G4Jy) catalog and based on equivalent selection criteria as the 3CR. This new catalog, named G4Jy-3CRE, where the E stands for “equivalent,” lists a total of 264 sources at decl. below −5° and with 9 Jy limiting sensitivity at ∼178 MHz. We explored archival radio maps obtained with different surveys and compared them with optical images available in the Pan-STARRS, DES, and DSS databases to search for optical counterparts of their radio cores. We compared mid-infrared counterparts, originally associated in the G4Jy, with the optical ones identified here, and we present results of a vast literature search carried out to collect redshift estimates for all G4Jy-3CRE sources resulting in a total of 145 reliable
z
measurements.
ABSTRACT
We present the Catalogue of High Resolution Spectra of Obscured Sources (CHRESOS) from the XMM–Newton Science Archive. It comprises the emission-line luminosities of H- and He-like ...transitions from C to Si, and the Fe 3C and Fe 3G L-shell ones. Here, we concentrate on the soft X-ray O vii (f) and O viii Lyα emission lines to shed light on to the physical processes with which their formation can be related to active galactic nucleus (AGN) versus star-forming regions. We compare their luminosity with that of two other important oxygen key lines O iii λ5007 Å, in the optical, and O iv 25.89 μm, in the infrared (IR). We also test O vii (f) and O viii Lyα luminosities against that of continuum bands in the IR and hard X-rays, which point to different ionization processes. We probe into those processes by analysing photoionization and collisional ionization model predictions upon our lines. We show that both scenarios can explain the formation and observed intensities of O vii (f) and O viii Lyα. By analysing the relationships between O vii (f) and O viii Lyα, and all other observables: O iii λ5007 Å, O iv 25.89 μm emission lines, and mid-infrared (MIR) 12 μm, far-infrared (FIR) 60 and 100 μm, 2–10 and 14–195 keV continuum bands, we conclude that the AGN radiation field is mainly responsible of the soft X-ray oxygen excitation.
We present new Gemini spectroscopical data of the extended emission-line region of the 3C 305 radio galaxy in order to achieve a final answer to the long-standing question about the ionizing ...mechanism. The spectra show strong kinematic disturbances within the most intense line-emitting region. The relative intensities of the emission lines agree with the hypothesis that the gas is shocked during the interaction of powerful radio jets with the ambient medium. The emission from the recombination region acts as a very effective cooling mechanism, which is supported by the presence of a neutral outflow. However, the observed intensity is almost an order of magnitude lower than expected in a pure shock model. So, autoionizing shock models, in low-density and low-abundance regimes, are required in order to account for the observed emission within the region. This scenario also supports the hypothesis that the optical emitting gas and the X-ray plasma are in pressure balance.
We present results of Gemini spectroscopy and Hubble Space Telescope imaging of the 3C 381 radio galaxy. Possible ionizing mechanisms for the extended emission-line region were studied through ...state-of-the-art diagnostic analysis employing line ratios. Photoionization from the central engine as well as mixed medium photoionization models fail in reproducing both the strengths and the behaviour of the highest excitation lines, such as Ne vλ3424, He ii and O iiiλ5007, which are measured at very large distances from the active galactic nucleus. Shock-ionization models provide a better fit to the observation. Expanding shocks with velocities higher than 500 km s−1 are capable of reaching the observed intensity ratios for lines with different ionization states and excitation degrees. This model also provides a direct explanation of the mechanical energy input needed to explain the high-velocity line-splitting observed in the velocity field.
The nature of a substantial percentage (about one fifth) of hard X-ray sources discovered with the BAT instrument onboard the
Neil Gehrels Swift Observatory
(hereafter Swift) is unknown because of ...the lack of an identified longer-wavelength counterpart. Without such follow-up, an X-ray catalogue is of limited astrophysical value: we therefore embarked, since 2009, on a long-term project to uncover the optical properties of sources identified by Swift by using a large suite of ground-based telescopes and instruments.
In this work, we continue our programme of characterization of unidentified or poorly studied hard X-ray sources by presenting the results of an optical spectroscopic campaign aimed at pinpointing and classifying the optical counterparts of 35 hard X-ray sources taken from the 70-month BAT catalogue. This sample was selected out of the available information about the chosen objects: either they are completely unidentified sources, or their association with a longer-wavelength counterpart is still ambiguous.
With the use of optical spectra taken at six different telescopes we were able to identify the main spectral characteristics (continuum type, redshift, and emission or absorption lines) of the observed objects, and determined their nature.
We identify and characterize a total of 41 optical candidate counterparts corresponding to 35 hard X-ray sources given that, because of positional uncertainties, multiple lower energy counterparts can sometimes be associated with higher energy detections. We discuss which ones are the actual (or at least most likely) counterparts based on our observational results.
In particular, 31 sources in our sample are active galactic nuclei: 16 are classified as Type 1 (with broad and narrow emission lines) and 13 are classified as Type 2 (with narrow emission lines only); two more are BL Lac-type objects. We also identify one LINER, one starburst, and 3 elliptical galaxies. The remaining 5 objects are galactic sources: we identify 4 of them as cataclysmic variables, whereas one is a low mass X-ray binary.
Context.
The
γ
-ray emitting source WISE J141046.00+740511.2 has been associated with a
Fermi
-LAT detection by crossmatching with
Swift
/XRT data. It has shown all the canonical observational ...characteristics of a BL Lac source, including a power-law, featureless optical spectrum. However, it was only recently detected at radio frequencies and its radio flux is significantly low.
Aims.
Given that a radio detection is fundamental to associate lower-energy counterparts to
Fermi
-LAT sources, we aim to unambiguously classify this source by performing a multiwavelength analysis based on contemporaneous data.
Methods.
By using multifrequency observations at the
Jansky
Very Large Array, Giant Metrewave Radio Telescope, Gran Telescopio Canarias, Gemini,
William Herschel
Telescope and Liverpool observatories, together with
Fermi
-LAT and
Swift
data, we carried out two kinds of analyses. On one hand, we studied several known parameters that account for the radio loudness or weakness characterization and their application to blazars (in general) and to our source (in particular). And, on the other hand, we built and analyzed the observed spectral energy distribution (SED) of this source to try to explain its peculiar characteristics.
Results.
The multiwavelength analysis indicates that WISE J141046.00+740511.2 is a blazar of the high-frequency peaked (HBL) type that emits highly polarized light and that is likely located at a low redshift. In addition, the one-zone model parameters that best fit its SED are those of an extreme HBL (EHBL); this blazar type has been extensively predicted in theory to be lacking in the radio emission that is otherwise typical of canonical
γ
-ray blazars.
Conclusions.
We confirm that WISE J141046.00+740511.2 is indeed a highly polarized BL Lac of the HBL type. Further studies will be conducted to explain the atypical low radio flux detected for this source.
We investigate the ionization state of the Extended Emission-Line Regions (EELRs) around two compact steep-spectrum (CSS) radio galaxies, 3C~268.3 and 3C~303.1, in order to identify the contribution ...of photoionization and shock-ionization. We perform a new spectroscopical (long-slit) analysis with GMOS/Gemini with the slit oriented in the radio-jet direction, where outflows are known to exist. The Ne V\(\lambda 3426\) emission is the most interesting feature of the spectra and the key to breaking the degeneracy between the models: since this emission-line is more extended than HeII, it challenges the ionization structure proposed by any photoionization model, also its intensity relative to H\(\beta\) does not behave as expected with respect to the ionization parameter U in the same scenario. On the contrary, when it is compared to the intensity of OII\(\lambda3727\)/H\(\beta\) and all these results are joined, the whole scenario is plausible to be explained as emission coming from the hot, compressed, shocked gas in shock-ionization models. Although the model fitting is strongly sensitive to the chosen line-ratios, it argues for the presence of external and strong ionizing fields, such as the precursor field created by the shock or/and the AGN radiation field. In this paper, we show how AGN photoionization and shock-ionization triggered by jet-cloud interaction work together in these EELRs in order to explain the observed trends and line-ratio behaviours in a kinematically acceptable way.
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