- ID:
- ivo://CDS.VizieR/J/ApJ/862/151
- Title:
- MOJAVE. XVI: parsec-scale AGN jet cores at 15GHz
- Short Name:
- J/ApJ/862/151
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of the core linear polarization properties of 387 parsec-scale active galactic nuclei (AGNs) jets. Using 15GHz VLBA data, we revisit the conclusions of the first paper in this series with multiepoch measurements and more detailed analysis of a larger AGN sample that spans a broader range of synchrotron peak frequencies. Each AGN has been observed for at least five epochs between 1996 and 2017. We find that BL Lac objects have core electric vector position angles (EVPAs) that tend toward alignment with the local jet direction; compared to flat spectrum radio quasars, their EVPAs are also less variable over time. The AGN cores that are most fractionally polarized and least variable in polarization have EVPAs that are closely aligned with the local jet direction; they also have low variability in EVPA. These results support the popular model of a standing transverse shock at the base of the jet that collimates the jet magnetic field perpendicular to the jet direction, increasing the fractional polarization and leading to greater polarization stability over time. High-synchrotron-peaked BL Lac objects form a low luminosity, low fractional polarization population. The five narrow line Seyfert 1 galaxies in our sample have low fractional polarization and large EVPA-jet misalignments. Although AGNs detected at {gamma}-rays are thought to be more Doppler boosted than nondetected AGNs, we find no significant differences in fractional polarization based on detection by Fermi-LAT; the {gamma}-loud AGNs are, however, more variable in core EVPAs.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJS/234/12
- Title:
- MOJAVE XV. VLBA 15GHz obs. of AGN jets 1996-2016
- Short Name:
- J/ApJS/234/12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 5321 mas-resolution total intensity and linear polarization maps of 437 active galactic nuclei (AGNs) obtained with the VLBA at 15GHz as part of the MOJAVE survey, and also from the NRAO data archive. The former is a long-term program to study the structure and evolution of powerful parsec-scale outflows associated with AGNs. The targeted AGNs are drawn from several flux-limited radio and {gamma}-ray samples, and all have correlated VLBA flux densities greater than ~50mJy at 15GHz. Approximately 80% of these AGNs are associated with {gamma}-ray sources detected by the Fermi LAT instrument. The vast majority were observed with the VLBA on 5-15 occasions between 1996 January 19 and 2016 December 26, at intervals ranging from a month to several years, with the most typical sampling interval being six months. A detailed analysis of the linear and circular polarization evolutions of these AGN jets is presented in the other papers in this series.
- ID:
- ivo://CDS.VizieR/J/ApJ/705/144
- Title:
- Molecular and atomic gas in the LMC. II.
- Short Name:
- J/ApJ/705/144
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We compare the CO (J=1-0) and HI emission in the Large Magellanic Cloud in three dimensions, i.e., including a velocity axis in addition to the two spatial axes, with the aim of elucidating the physical connection between giant molecular clouds (GMCs) and their surrounding HI gas. The CO(J=1-0) data set is from the second NANTEN CO survey (Fukui et al. 2008, Cat. J/ApJS/178/56) and the HI data set is from the merged Australia Telescope Compact Array (ATCA) and Parkes Telescope surveys (Kim et al. 2003ApJS..148..473K).
- ID:
- ivo://CDS.VizieR/J/ApJ/872/121
- Title:
- Molecular cloud cores in the GC 50km/s cloud
- Short Name:
- J/ApJ/872/121
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Galactic center 50km/s molecular cloud (50MC) is the most remarkable molecular cloud in the Sagittarius A region. This cloud is a candidate for the massive star formation induced by cloud-cloud collision (CCC) with a collision velocity of ~30km/s that is estimated from the velocity dispersion. We observed the whole of the 50MC with a high angular resolution (~2.0"x1.4") in Atacama Large Millimeter/submillimeter Array cycle 1 in the H^13^CO^+^ J=1-0 and C^34^S J=2-1 emission lines. We identified 241 and 129 bound cores with a virial parameter of less than 2, which are thought to be gravitationally bound, in the H^13^CO^+^ and C^34^S maps using the clumpfind algorithm, respectively. In the CCC region, the bound H^13^CO^+^ and C^34^S cores are 119 and 82, whose masses are 68% and 76% of those in the whole 50MC, respectively. The distribution of the core number and column densities in the CCC are biased to larger densities than those in the non-CCC region. The distributions indicate that the CCC compresses the molecular gas and increases the number of the dense bound cores. Additionally, the massive bound cores with masses of >3000M_{sun}_ exist only in the CCC region, although the slope of the core mass function (CMF) in the CCC region is not different from that in the non-CCC region. We conclude that the compression by the CCC efficiently formed massive bound cores even if the slope of the CMF is not changed so much by the CCC.
- ID:
- ivo://CDS.VizieR/J/ApJS/184/1
- Title:
- Molecular clouds in the LMC by NANTEN. II.
- Short Name:
- J/ApJS/184/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We studied star formation activities in the molecular clouds in the Large Magellanic Cloud. We have utilized the second catalog of 272 molecular clouds obtained by NANTEN (4m radio telescope of Nagoya University at Las Campanas Observatory, Chile) to compare the cloud distribution with signatures of massive star formation including stellar clusters, and optical and radio HII regions. We find that the molecular clouds are classified into three types according to the activities of massive star formation: Type I shows no signature of massive star formation; Type II is associated with relatively small HII region(s); and Type III with both HII region(s) and young stellar cluster(s). The radio continuum sources were used to confirm that Type I giant molecular clouds (GMCs) do not host optically hidden HII regions. These signatures of massive star formation show a good spatial correlation with the molecular clouds in the sense that they are located within ~100pc of the molecular clouds.
- ID:
- ivo://CDS.VizieR/J/ApJ/828/59
- Title:
- Molecular clouds in the Milky Way with CO obs.
- Short Name:
- J/ApJ/828/59
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Galactic plane has been mapped from l=34.75{deg} to 45.25{deg} and b=-5.25{deg} to 5.25{deg} in the CO (J=1-0) emission with the 13.7m telescope of the Purple Mountain Observatory. The unbiased survey covers a large area of 110 square degrees sampled every 30" with a velocity resolution of ~0.2km/s. In this paper, we present the result of an unbiased CO survey of this longitude and latitude range in the velocity range from -60 to -10km/s. Over 500 molecular clouds (MCs) are picked out from the ^12^CO (J=1-0) emission, and 131 of these MCs are associated with ^13^CO emission. The distant MCs, which lie beyond the solar circle and are mostly concentrated in the Galactic plane, trace the large-scale molecular gas structure over 10 degrees of Galactic azimuth. We find that the distribution of the distant MCs can be well fitted by a Gaussian function with a full width at half maximum (FWHM) of 0.7{deg} with the Galactic latitude. We suggest that the CO emission of the segment is from the Outer Arm. The physical mid-plane traced by the Outer Arm seems to be slightly displaced from the IAU-defined plane on a large scale, which could be explained by the warped plane at large Galactocentric distances of >~10kpc and the apparent tilted mid-plane to the projected IAU-defined plane caused by the Sun's z-height above the disk for distances near and within the Solar circle. After removing the effect of the warp and tilted structure, the scale height of the MCs in the Outer Arm is about 0.6{deg} or 160pc at a heliocentric distance of 15kpc. If the inner plane of our Galaxy is flat, we can derive an upper limit of the Sun's offset of ~17.1pc above the physical mid-plane of the Milky Way. We also discuss the correlations between the physical parameters of the distant MCs, which is quite consistent with the result of other studies of this parameter.
- ID:
- ivo://CDS.VizieR/J/A+AS/144/441
- Title:
- Molecular clouds SO and CS obs. I.
- Short Name:
- J/A+AS/144/441
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the article we present a rather extensive mapping survey of 19 molecular clouds in the SO(3_2_-2_1_) and CS(2-1) molecular lines and, at certain positions, also the corresponding 34S isotope lines. Here we present the maps of the survey.
- ID:
- ivo://CDS.VizieR/J/A+A/358/257
- Title:
- Molecular clouds SO and CS obs. II.
- Short Name:
- J/A+A/358/257
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We here analyse the observational SO and CS data presented in Nilsson et al. (2000A&AS..144..441N). The SO/CS integrated intensity ratio maps are presented for 19 molecular clouds, together with tables of relevant ratios at strategic positions, where w e have also observed ^34^SO and/or C^34^S.
- ID:
- ivo://CDS.VizieR/J/A+A/327/522
- Title:
- Molecular gas content of spiral galaxies
- Short Name:
- J/A+A/327/522
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 12CO(J=1-0) line observations of 73 spiral galaxies mostly in the Coma/A1367 supercluster. From these data, combined with data available in the literature, we extract the first complete, optically selected sample (mpg<15.2) of 37 isolated and of 27 cluster galaxies. The 12CO(1-0) line spectra are accessible as postscript figures.
- ID:
- ivo://CDS.VizieR/J/ApJ/710/150
- Title:
- Molecular lines in EGOs
- Short Name:
- J/ApJ/710/150
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the first systematic survey of molecular lines (including HCO^+^(1-0) and ^12^CO, ^13^CO, C^18^O(1-0) lines at the 3mm band) toward a new sample of 88 massive young stellar object (MYSO) candidates associated with ongoing outflows (known as extended green objects or EGOs) identified from the Spitzer GLIMPSE survey in the northern hemisphere with the Purple Mountain Observatory 13.7m radio telescope. By analyzing the asymmetries of the optically thick line HCO^+^ for 69 of 72 EGOs with HCO^+^ detection, we found 29 sources with "blue asymmetric profiles" and 19 sources with "red asymmetric profiles."