- ID:
- ivo://CDS.VizieR/J/A+A/632/A13
- Title:
- NGC 4013 radio and polarization maps
- Short Name:
- J/A+A/632/A13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- From the Continuum HAloes in Nearby Galaxies - an EVLA Survey (CHANG-ES) radio continuum data from the Karl G. Jansky Very Large Array (VLA), observed in two frequency bands, 6GHz (C-band) and 1.5GHz (L-band), we present the radio maps, including polarization of the edge-on spiral galaxy NGC 4013. Supplemantary X-ray data are also presented here. The central point source of NGC 4013 dominates the radio continuum emission in both CHANG-ES bands. Complementary X-ray data from Chandra show one dominant point source in the central part. The XMM-Newton spectrum shows hard X-rays, but no clear AGN classification is possible at this time. The radio continuum halo of NGC 4013 in C-band is rather small, while the low-frequency LOFAR data reveal a large halo. The scale height analysis shows that Gaussian fits better represent the intensity profiles than do exponential fits. The frequency dependence gives clear preference to diffusive CRE transport. The radio halo of NGC 4013 is relatively faint. Diffusion is the dominating transport process up to heights of 1-2kpc. The polarization data reveal plane-parallel, regular magnetic fields within the entire disk and vertical halo components indicating the presence of an axisymmetric field having a radial component pointing outwards. The mean magnetic field strength of the disk of NGC 4013 of 6.6{mu}G is rather small. Large-scale vertical fields are observed in the halo out to heights of about 6kpc. The interaction and the low star formation rate (SFR) across the disk of NGC 4013 probably influence the appearance of its radio continuum halo and are correlated with the low total magnetic field strength. Several observable quantities give consistent evidence that the CR transport in the halo of NGC 4013 is diffusive: the frequency dependence of the synchrotron scale height, the disk/halo flux density ratio, the vertical profile of the synchrotron spectral index, the small propagation speed measured modeled with spinnaker, and the low temperature of the X-ray emitting hot gas.
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- ID:
- ivo://CDS.VizieR/J/A+A/639/A111
- Title:
- NGC 4217 radio and polarization maps
- Short Name:
- J/A+A/639/A111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the radio continuum halo, the magnetic field, and the transport processes of the CRs of the edge-on spiral galaxy NGC 4217 using Continuum HAlos in Nearby Galaxies - an Evla Survey (CHANG-ES) radio data at two frequencies, 6GHz (C-band) and 1.5GHz (L-band), and supplemental LOFAR data of this galaxy at 150MHz. With additional X-ray Chandra data, we study the connection of radio features to the diffuse hot gas around NGC 4217. NGC 4217 shows a large-scale X-shaped magnetic field structure, covering a major part of the galaxy with a mean total magnetic field strength in the disk of 9G. From the analysis of the rotation measure map at C-band, we found that the direction of the disk magnetic field is pointing inward. A helical outflow structure is furthermore present in the northwestern part of the galaxy, which is extended nearly 7 kpc into the halo. More polarized emission is observed on the approaching side of the galaxy, indicating that Faraday depolarization has to be considered at C-band. With a simplified galaxy disk model, we are able to explain the finding of higher polarized intensity on the approaching side. We generalize the model to predict that roughly 75% of edge-on spiral galaxies will show higher polarized intensity on the approaching side. Many loop and shell structures are found throughout the galaxy in total intensity at C-band. One structure, a symmetric off-center (to the southwest of the disk) superbubble-like structure is prominent in total and polarized intensity, as well as in Halpha and optical dust filaments. This is at a location where a second peak of total intensity (to the southwest of the disk) is observed, making this superbubble-like structure a possible result of a concentrated star formation region in the disk. The X-ray diffuse emission shows similarities to the polarized diffuse emission of NGC 4217. The flux density extension of the radio continuum halo increases toward lower frequencies. While the total flux density of the disk and halo are comparable at C-band, the contribution of the disk flux density decreases toward LOFAR to 18% of the total flux density. Dumbbell-shaped structures are present at C-band and at the LOFAR frequency. Total intensity profiles at the two CHANG-ES bands and the LOFAR frequency show a clear two-component behavior and were fit best with a two-component exponential fit. The halo scale heights are 1.10+/-0.04kpc, 1.43+/-0.09kpc, and 1.55+/-0.04kpc in C-band, L-band, and 150MHz, respectively. The frequency dependence of these scale heights between C-band and L-band suggests advection to be the main transport process. The 1D CRE transport modeling shows that advection appears to be more important than diffusion.
- ID:
- ivo://CDS.VizieR/J/A+A/647/A78
- Title:
- NGC6334 850um I, Q, U Stokes parameter maps
- Short Name:
- J/A+A/647/A78
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Molecular filaments and hubs have received special attention recently thanks to new studies showing their key role in star formation. While the (column) density and velocity structures of both filaments and hubs have been carefully studied, their magnetic field (B-field) properties have yet to be characterized. Consequently, the role of B-fields in the formation and evolution of hub-filament systems is not well constrained. We aim to understand the role of the B-field and its interplay with turbulence and gravity in the dynamical evolution of the NGC 6334 filament network that harbours cluster-forming hubs and high-mass star formation. We present new observations of the dust polarized emission at 850mum toward the 2pcx10pc map of NGC 6334 at a spatial resolution of 0.09pc obtained with the James Clerk Maxwell Telescope (JCMT) as part of the B-field In STar-forming Region Observations (BISTRO) survey. We study the distribution and dispersion of the polarized intensity (PI), the polarization fraction (PF), and the plane-of-the-sky (POS) B-field angle ({chi}B_POS_) toward the whole region, along the 10pc-long ridge and along the sub-filaments connected to the ridge and the hubs. We derived the power spectra of the intensity and {chi}B_POS_ along the ridge crest and compared them with the results obtained from simulated filaments. The observations span ~3 orders of magnitude in I and PI and ~2 orders of magnitude in PF (from ~0.2% to ~20%). A large scatter in PI and PF is observed for a given value of I. Our analyzes show a complex B-field structure when observed over the whole region (~10pc); however, at smaller scales (~1pc), {chi}B_POS_ varies coherently along the crests of the filament network. The observed power spectrum of {chi}B_POS_ can be well represented with a power law function with a slope of -1.33+/-0.23, which is ~20% shallower than that of I. We find that this result is compatible with the properties of simulated filaments and may indicate the physical processes at play in the formation and evolution of star-forming filaments. Along the sub-filaments, {chi}B_POS_ rotates from being mostly perpendicular or randomly oriented with respect to the crests to mostly parallel as the sub-filaments merge with the ridge and hubs. This variation of the B-field structure along the sub-filaments may be tracing local velocity flows of infalling matter in the ridge and hubs. Our analysis also suggests a variation in the energy balance along the crests of these sub-filaments, from magnetically critical or supercritical at their far ends to magnetically subcritical near the ridge and hubs. We also detect an increase in PF toward the high-column density (N_H2_>~10^23^cm^-2^) star cluster-forming hubs. These latter large PF values may be explained by the increase in grain alignment efficiency due to stellar radiation from the newborn stars, combined with an ordered B-field structure. These observational results reveal for the first time the characteristics of the small-scale (down to ~0.1pc) B-field structure of a 10pc-long hub-filament system. Our analyzes show variations in the polarization properties along the sub-filaments that may be tracing the evolution of their physical properties during their interaction with the ridge and hubs. We also detect an impact of feedback from young high-mass stars on the local B-field structure and the polarization properties, which could put constraints on possible models for dust grain alignment and provide important hints as to the interplay between the star formation activity and interstellar B-fields.
- ID:
- ivo://CDS.VizieR/J/ApJ/867/79
- Title:
- NIR observations of GF 9/LDN 1082C field stars
- Short Name:
- J/ApJ/867/79
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The orientation of the magnetic field (B field) in the filamentary dark cloud GF 9 was traced from the periphery of the cloud into the L1082C dense core that contains the low-mass, low-luminosity Class 0 young stellar object (YSO) GF 9-2 (IRAS 20503+6006). This was done using SOFIA HAWC+ dust thermal emission polarimetry (TEP) at 216{mu}m in combination with Mimir near-infrared background starlight polarimetry (BSP) conducted in the H band (1.6{mu}m) and K band (2.2{mu}m). These observations were augmented with published I-band (0.77{mu}m) BSP and Planck 850{mu}m TEP to probe B-field orientations with offset from the YSO in a range spanning 6000au to 3pc. No strong B-field orientation change with offset was found, indicating remarkable uniformity of the B-field from the cloud edge to the YSO environs. This finding disagrees with weak-field models of cloud core and YSO formation. The continuity of inferred B-field orientations for both TEP and BSP probes is strong evidence that both are sampling a common B field that uniformly threads the cloud, core, and YSO region. Bayesian analysis of Gaia DR2 stars matched to the Mimir BSP stars finds a distance to GF 9 of 270+/-10pc. No strong wavelength dependence of B-field orientation angle was found, contrary to previous claims.
- ID:
- ivo://CDS.VizieR/J/ApJ/741/35
- Title:
- NIR photometry and polarization in NGC 2264
- Short Name:
- J/ApJ/741/35
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Near-infrared imaging polarimetry in the J, H, and Ks bands has been carried out for the protostellar cluster region around NGC 2264 IRS 2 in the Monoceros OB1 molecular cloud. Various infrared reflection nebula clusters (IRNCs) associated with NGC 2264 IRS 2 and the IRAS 12 S1 core, as well as local infrared reflection nebulae (IRNe), were detected. The illuminating sources of the IRNe were identified with known or new near- and mid-infrared sources. In addition, 314 point-like sources were detected in all three bands and their aperture polarimetry was studied. Using a color-color diagram, reddened field stars and diskless pre-main-sequence stars were selected to trace the magnetic field (MF) structure of the molecular cloud. The mean polarization position angle of the point-like sources is 81+/-29{deg} in the cluster core, and 58+/-24{deg} in the perimeter of the cluster core, which is interpreted as the projected direction on the sky of the MF in the observed region of the cloud. The Chandrasekhar-Fermi method gives a rough estimate of the MF strength to be about 100uG. A comparison with recent numerical simulations of the cluster formation implies that the cloud dynamics is controlled by the relatively strong MF. The local MF direction is well associated with that of CO outflow for IRAS 12 S1 and consistent with that inferred from submillimeter polarimetry. In contrast, the local MF direction runs roughly perpendicular to the Galactic MF direction.
- ID:
- ivo://CDS.VizieR/J/ApJS/213/22
- Title:
- NIR polarimetry in the Central Molecular Zone
- Short Name:
- J/ApJS/213/22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have carried out near-infrared polarimetry toward the boundary of the Central Molecular Zone, in the field of (-1.{deg}4<~l<~-0.{deg}3 and 1.{deg}0<~l<~2.{deg}9,|b|<~0.{deg}1), using the near-infrared polarimetric camera SIRPOL on the 1.4m Infrared Survey Facility telescope. We have selected 112 intrinsically polarized sources on the basis of the estimate of interstellar polarization on Stokes Q/I-U/I planes. The selected sources are brighter than K_S_=14.5mag and have polarimetric uncertainty {delta}P<1%. Ten of these distinctive polarized sources are fit well with spectral energy distributions of young stellar objects when using the photometry in the archive of the Spitzer Space Telescope mid-infrared data. However, many sources have spectral energy distributions of normal stars suffering from heavy interstellar extinction; these might be stars behind dark clouds. Due to the small number of distinctive polarized sources and candidates of young stellar objects, we cannot judge if they are declining in number outside the Central Molecular Zone. Many massive candidates for young stellar objects in the literature have only small intrinsic polarization. This might suggest that their masses are 4-15M_{sun}_, whose intrinsic polarization has been expected to be small.
- ID:
- ivo://CDS.VizieR/J/A+A/534/A117
- Title:
- NIR polarimetry of sources near SgrA*
- Short Name:
- J/A+A/534/A117
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Galactic Center offers unique opportunities to study stellar and bow-shock polarization effects in a dusty environment. The goals of this work are to provide near-infrared (NIR) polarimetry of the stellar sources in the central parsec at the resolution of an 8m telescope for the first time, along with new insights into the nature of the known bright bow-shock sources. We use adaptive-optics assisted observations obtained at the ESO VLT in the H- and Ks-band, applying both high-precision photometric methods specifically developed for crowded fields and a newly established polarimetric calibration for NACO to produce polarization maps of the central 3"x10", in addition to spatially resolved polarimetry and a flux variability analysis on the extended sources in this region.
- ID:
- ivo://CDS.VizieR/J/ApJS/222/2
- Title:
- NIR sources in the northeastern part of LMC
- Short Name:
- J/ApJS/222/2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a near-infrared band-merged photometric and polarimetric catalog for the 39'x69' fields in the northeastern part of the Large Magellanic Cloud (LMC), which were observed using SIRPOL, an imaging polarimeter of the InfraRed Survey Facility. This catalog lists 1858 sources brighter than 14mag in the H band with a polarization signal-to-noise ratio greater than three in the J, H, or K_s_ bands. Based on the relationship between the extinction and the polarization degree, we argue that the polarization mostly arises from dichroic extinctions caused by local interstellar dust in the LMC. This catalog allows us to map polarization structures to examine the global geometry of the local magnetic field, and to show a statistical analysis of the polarization of each field to understand its polarization properties. In the selected fields with coherent polarization position angles, we estimate magnetic field strengths in the range of 3-25{mu}G using the Chandrasekhar-Fermi method. This implies the presence of large-scale magnetic fields on a scale of around 100 parsecs. When comparing mid- and far-infrared dust emission maps, we confirmed that the polarization patterns are well aligned with molecular clouds around the star-forming regions.
- ID:
- ivo://CDS.VizieR/J/ApJS/2/389
- Title:
- Observations of O and B stars
- Short Name:
- J/ApJS/2/389
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalog of O and B stars contains magnitudes, colors, spectral types and polarization for 1259 stars. In addition to observations, the catalogue contains the derived absorption and distance modulus. A photoelectric photometer attached to the 82-inch (2m) reflector of the McDonald Observatory was used for the polarization observations. The photometric UBV observations were made over a period of 4 years with the 13-inch (33cm) and the 82-inch telescopes at McDonald. The spectroscopic classification was made with a new camera installed on the Cassegrain spectrograph, with a dispersion of 86{AA}/mm at H{delta}.
- ID:
- ivo://CDS.VizieR/J/ApJ/835/275
- Title:
- OJ 287 flux & polarization during 2016 outburst
- Short Name:
- J/ApJ/835/275
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The gamma-ray blazar OJ 287 was in a high activity state during 2015 December-2016 February. Coinciding with this high brightness state, we observed this source for photometry on 40 nights in R-band and for polarimetry on nine epochs in UBV RI bands. During the period of our observations, the source brightness varied from 13.20+/-0.04 mag to 14.98+/-0.04mag and the degree of polarization (P) fluctuated between 6.0%+/-0.3% and 28.3%+/-0.8% in R-band. Focusing on intranight optical variability (INOV), we find a duty cycle of about 71% using {chi}^2^-statistics, similar to that known for blazars. From INOV data, the shortest variability timescale is estimated to be 142+/-38min, yielding a lower limit of the observed Doppler factor {delta}_0_=1.17, the magnetic field strength B<=3.8G, and the size of the emitting region R_s_<2.28x10^14^cm. On internight timescales, a significant anticorrelation between R-band flux and P is found. The observed P at U-band is generally larger than that observed at longer-wavelength bands, suggesting a wavelength-dependent polarization. Using V-band photometric and polarimetric data from Steward Observatory obtained during our monitoring period, we find a varied correlation between P and V-band brightness. While an anticorrelation is sometimes seen between P and V-band magnitude, no correlation is seen at other times, thereby suggesting the presence of more than one short-lived shock component in the jet of OJ 287.
