- ID:
- ivo://CDS.VizieR/J/A+A/549/A17
- Title:
- IRAM spectra toward M33 Giant Molecular Clouds
- Short Name:
- J/A+A/549/A17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We aim to better understand the emission of molecular tracers of the diffuse and dense gas in giant molecular clouds and the influence that metallicity, optical extinction, density, far-UV field, and star formation rate have on these tracers. Using the IRAM 30m telescope, we detected HCN, HCO^+^, ^12^CO, and ^13^CO in six GMCs along the major axis of M33 at a resolution of ~114pc and out to a radial distance of 3.4kpc. Optical, far-infrared, and submillimeter data from Herschel and other observatories complement these observations. To interpret the observed molecular line emission, we created two grids of models of photon-dominated regions, one for solar and one for M33-type subsolar metallicity. The observed HCO^+^/HCN line ratios range between 1.1 and 2.5. Similarly high ratios have been observed in the Large Magellanic Cloud. The HCN/CO ratio varies between 0.4% and 2.9% in the disk of M33. The ^12^CO/^13^CO line ratio varies between 9 and 15 similar to variations found in the diffuse gas and the centers of GMCs of the Milky Way. Stacking of all spectra allowed HNC and C_2_H to be detected. The resulting HCO^+^/HNC and HCN/HNC ratios of ~8 and 6, respectively, lie at the high end of ratios observed in a large set of (ultra-)luminous infrared galaxies. HCN abundances are lower in the subsolar metallicity PDR models, while HCO^+^ abundances are enhanced. For HCN this effect is more pronounced at low optical extinctions. The observed HCO^+^/HCN and HCN/CO line ratios are naturally explained by subsolar PDR models of low optical extinctions between 3 and 10mag and of moderate densities of n=3x10^3^-3x10^4^cm^-3^, while the FUV field strength only has a small effect on the modeled line ratios. The line ratios are almost equally well reproduced by the solar-metallicity models, indicating that variations in metallicity only play a minor role in influencing these line ratios.
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- ID:
- ivo://CDS.VizieR/J/MNRAS/449/3191
- Title:
- IR photometry of nearby RLGs
- Short Name:
- J/MNRAS/449/3191
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- By combining the data of the Two Micron All Sky Survey, the Wide-Field Infrared Survey Explorer and the AKARI satellite, we study the infrared colour properties of a sample of 2712 nearby radio-luminous galaxies (RLGs). These RLGs are divided into radio-loud (RL) active galactic nuclei (AGNs), mainly occurring at redshifts of 0.05<z<0.3 and star-forming-dominated RLGs (SFGs), mainly occurring at redshifts of 0.01<z<0.15. RL AGNs and SFGs are separately distributed in the ([3.4]-[4.6])-([4.6]-[12]) two-colour diagram, in which the RL AGNs display a double-core distribution, and the SFGs display a single-core distribution. SFGs have a redder [4.6]-[12] colour than RL AGNs due to the significant contribution from the dust component of SFGs. We find simple criteria of mid-infrared (MIR) colour separation between RL AGNs and SFGs such that: 95 per cent of RL AGNs have [4.6]-[12]<3.0 and 94 per cent of SFGs have [4.6]-[12]>3.0. We also analyse the MIR colours of RL AGNs divided into low- and high-excitation radio galaxies (LERGs and HERGs, respectively). The ([3.4]-[4.6])-([4.6]-[12]) diagram clearly shows separate distributions of LERGs and HERGs and a region of overlap, which suggests that LERGs and HERGs have different MIR properties. LERGs are responsible for the double-core distribution of RL AGNs on the ([3.4]-[4.6])-([4.6]-[12]) diagram. In addition, we also suggest 90-140{mu}m band spectral index {alpha}(90, 140)<-1.4 as a criterion of selecting nearby active galaxies with non-thermal emissions at far-infrared wavelengths.
- ID:
- ivo://CDS.VizieR/J/A+A/658/A119
- Title:
- Jet collimation in NGC 1052
- Short Name:
- J/A+A/658/A119
- Date:
- 22 Feb 2022 14:52:38
- Publisher:
- CDS
- Description:
- With the increased sensitivity and resolution of radio interferometry the study of the collimation and acceleration region of jets in Active Galactic Nuclei(AGN) has come into focus within the last years. Whereas a large fraction of AGN jets reveal a change from parabolic to conical collimation around the Bondi radius, a small number of sources deviate from this standard picture, including the radio galaxy NGC1052. We study the jet width profile, which provides valuable information about the interplay between the central engine and accretion disk system and the collimation and acceleration zone of the jets. We observed the double-sided active galaxy NGC1052 at six frequencies with the VLBA in 2017 and at 22GHz with RadioAstron in 2016. These data are combined with archival 15, 22, and 43GHz multi-epoch VLBA observations. From ridge-line fitting we obtained width measurements along the jet and counter-jet which were fitted with broken power-laws. We find a break in the jet collimation profile at ~10^4^R_s_ (Schwarzschild radii). Downstream of the break the collimation is conical with a power-law index of 1.0-1.2 (cylindrical 0; parabolic 0.5; conical 1). The upstream power-law index of 0.36 for the approaching jet is neither cylindrical nor parabolic and for the receding jet with 0.16 close-to cylindrical. Both jets have an opening angle of ~30 degree at a distance of ~10^3R_S_ and are well collimated with an opening angle of <10 degrees downstream of the break. There are significant differences in the upstream collimation profile between approaching (Eastern) and receding (Western) jet. Absorption or scattering in the surrounding torus as well as an accretion wind may mimic a cylindrical profile. We need to increase the observing frequencies, which do not suffer from absorption to find the true jet collimation profile upstream of 10^4^R_s_.
- ID:
- ivo://CDS.VizieR/J/A+A/647/A67
- Title:
- Jet collimation in NGC 315
- Short Name:
- J/A+A/647/A67
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The collimation of relativistic jets in galaxies is a poorly understood process. Detailed radio studies of the jet collimation region have been performed so far in a few individual objects, providing important constraints for jet formation models. However, the extent of the collimation zone as well as the nature of the external medium possibly confining the jet are still debated. In this article, we present a multifrequency and multiscale analysis of the radio galaxy NGC 315, including the use of mm-VLBI data up to 86GHz, aimed at revealing the evolution of the jet collimation profile. We then consider results from the literature to compare the jet expansion profile in a sample of 27 low-redshift sources, mainly comprising radio galaxies and BL Lacs, which were classified based on the accretion properties as low-excitation (LEG) and high-excitation (HEG) galaxies. We propose that the jet collimation in NGC 315 is completed on sub-parsec scales. A transition from a parabolic to conical jet shape is detected at z_t_=0.58+/-0.28-parsecs or ~5x10^3& Schwarzschild radii (Rs) from the central engine, a distance which is much smaller than the Bondi radius, rB~92pc, estimated based on X-ray data. The jet in this and in a few other LEG in our sample may be initially confined by a thick disk extending out to ~10^3^-10^4^R_{sun}_. A comparison between the mass-scaled jet expansion profiles of all sources indicates that jets in HEG are surrounded by thicker disk-launched sheaths and collimate on larger scales with respect to jets in LEG. These results suggest that disk winds play an important role in the jet collimation mechanism, particularly in high-luminosity sources. The impact of winds on the origin of the FRI and FRII dichotomy in radio galaxies is also discussed.
- ID:
- ivo://CDS.VizieR/J/A+A/298/375
- Title:
- Jet-disk symbiosis II
- Short Name:
- J/A+A/298/375
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the correlation between the accretion disk (UV) luminosity and the radio core emission of a quasar sample, containing all PG quasars, also deriving empirical conversion factors from emission line luminosities to disk luminosities. This method allows us to investigate the radio properties of AGN on the absolute scale set by the accretion power. The tables contain the quasar (and radio galaxy) sample discussed in this paper (including the complete PG quasars sample) and give the derived `disk luminosities' of the UV-bump and 5GHz radio luminosities.
- ID:
- ivo://CDS.VizieR/J/A+AS/98/393
- Title:
- 1Jy BL Lac Objects: Observational Data
- Short Name:
- J/A+AS/98/393
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Direct imaging and spectroscopic data are reported for the complete sample of 34 BL Lac objects selected from the 1Jy source catalogue (see Cat. <VIII/5>). A short description of each individual object is given along with a general discussion of the features observed in the optical spectra, the optical morphologies, and the environments of the BL Lac objects.
- ID:
- ivo://CDS.VizieR/J/ApJS/247/71
- Title:
- Large-scale environment of radio galaxies. II.
- Short Name:
- J/ApJS/247/71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In our previous analysis we investigated the large-scale environment of two samples of radio galaxies (RGs) in the local universe (i.e., with redshifts z_src_<=0.15), classified as FR I and FR II on the basis of their radio morphology. The analysis was carried out using (i) extremely homogeneous catalogs and (ii) a new method, known as cosmological overdensity, to investigate their large-scale environments. We concluded that, independently of the shape of their radio extended structure, RGs inhabit galaxy-rich large-scale environments with similar characteristics and richness. In the present work, we first highlight additional advantages of our procedure, which does not suffer cosmological biases and/or artifacts, and then we carry out an additional statistical test to strengthen our previous results. We also investigate properties of RG environments using those of the cosmological neighbors. We find that large-scale environments of both FR Is and FR IIs are remarkably similar and independent of the properties of central RG. Finally, we highlight the importance of comparing radio sources in the same redshift bins to obtain a complete overview of their large-scale environments.
- ID:
- ivo://CDS.VizieR/J/MNRAS/317/801
- Title:
- LBDS Hercules sample griJHK photometry
- Short Name:
- J/MNRAS/317/801
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results are presented of an extensive programme of optical and infrared imaging of radio sources in a complete subsample of the Leiden-Berkeley Deep Survey. The LBDS Hercules sample consists of 72 sources observed at 1.4GHz, with flux densities S_1.4_>=1.0mJy, in a 1.2deg^2^ region of Hercules. This sample is almost completely identified in the g, r, i and K bands, with some additional data available at J and H. The magnitude distributions peak at r~22mag, K~6mag and extend down to r~26mag, K~21mag. The K-band magnitude distributions for the radio galaxies and quasars are compared with those of other radio surveys. At S_1.4GHz_<~1Jy, the K-band distribution does not change significantly with radio flux density. The sources span a broad range of colours, with several being extremely red (r-K>~6). Though small, this is the most optically complete sample of mJy radio sources available at 1.4GHz, and is ideally suited for studying the evolution of the radio luminosity function out to high redshifts.
- ID:
- ivo://CDS.VizieR/J/MNRAS/405/436
- Title:
- LBDS-Lynx region GMRT 150-MHz obs.
- Short Name:
- J/MNRAS/405/436
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- It has been known for nearly three decades that high-redshift radio galaxies exhibit steep radio spectra, and hence ultrasteep spectrum radio sources provide candidates for high-redshift radio galaxies. Nearly all radio galaxies with z>3 have been found using this redshift-spectral index correlation. We have started a programme with the Giant Metrewave Radio Telescope (GMRT) to exploit this correlation at flux density levels about 10 to 100 times deeper than the known high-redshift radio galaxies which were identified primarily using the already available radio catalogues. In our programme, we have obtained deep, high-resolution radio observations at 150MHz with GMRT for several "deep" fields which are well studied at higher radio frequencies and in other bands of the electromagnetic spectrum, with an aim to detect candidate high-redshift radio galaxies. In this paper we present results from the deep 150-MHz observations of the LBDS-Lynx field (Leiden-Berkeley Deep Survey), which has been already imaged at 327, 610 and 1412MHz with the Westerbork Synthesis Radio Telescope and at 1400 and 4860MHz with the Very Large Array.
- ID:
- ivo://CDS.VizieR/J/MNRAS/435/3376
- Title:
- L_FIR_ and L_CO_ for 247 extragalactic systems
- Short Name:
- J/MNRAS/435/3376
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- An analysis of 44GHz Very Large Array observations of the z=1.574 radio-loud quasar 3C 318 has revealed emission from the redshifted J=1-->0 transition of the CO molecule and spatially resolved the 6.3kpc radio jet associated with the quasar at 115GHz rest frame. The continuum-subtracted line emitter is spatially offset from the quasar nucleus by 0.33arcsec (2.82kpc in projection). This spatial offset has a significance of >8{sigma} and, together with a previously published -400km/s velocity offset measured in the J=2-->1 CO line relative to the systemic redshift of the quasar, rules out a circumnuclear starburst or molecular gas ring and suggests that the quasar host galaxy is either undergoing a major merger with a gas-rich galaxy or is otherwise a highly disrupted system. If the merger scenario is correct, then the event may be in its early stages, acting as the trigger for both the young radio jets in the quasar and a starburst in the merging galaxy. The total molecular gas mass in the spatially offset line emitter as measured from the ground-state CO line MH_2_=3.7(+/-0.4)x10^10^ ({alpha}CO/0.8)M_{sun}_. Assuming that the line emitter can be modelled as a rotating disc, an inclination-dependent upper limit is derived for its dynamical mass M_dyn_sin^2^(i)<3.2x10^9^M_{sun}_, suggesting that for MH2 to remain less than M_dyn_ the inclination angle must be i<16{deg}. The far-infrared and CO luminosities of 246 extragalactic systems are collated from the literature for comparison. The high molecular gas content of 3C 318 is consistent with that of the general population of high-redshift quasars and submillimetre galaxies.
