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81. GLOSTAR Galactic plane survey. II. SNR.
ID:
ivo://CDS.VizieR/J/A+A/651/A86
Title:
GLOSTAR Galactic plane survey. II. SNR.
Short Name:
J/A+A/651/A86
Date:
17 Jan 2022 00:20:41
Publisher:
CDS
Description:
The properties of the population of Galactic supernova remnants (SNRs) are essential to our understanding of the dynamics of the interstellar medium (ISM) in the Milky Way. However, the completeness of the catalog of Galactic SNRs is expected to be only ~30%, with on order 700 SNRs yet to be detected. Deep interferometric radio continuum surveys of the Galactic plane help in rectifying this apparent deficiency by identifying low surface brightness SNRs and compact SNRs that have not been detected in previous surveys. However, SNRs are routinely confused with HII regions, which can have similar radio morphologies. Radio spectral index, polarization, and emission at mid-infrared (MIR) wavelengths can help distinguish between SNRs and HII regions. We aim to identify SNR candidates using continuum images from the Karl G. Jansky Very Large Array GLObal view of the STAR formation in the Milky Way (GLOSTAR) survey. GLOSTAR is a C-band (4-8GHz) radio wavelength survey of the Galactic plane covering 358{deg}>=l<=60{deg}, |b|<=1{deg}. The continuum images from this survey, which resulted from observations with the most compact configuration of the array, have an angular resolution of 18''. We searched for SNRs in these images to identify known SNRs, previously identified SNR candidates, and new SNR candidates. We study these objects in MIR surveys and the GLOSTAR polarization data to classify their emission as thermal or nonthermal. We identify 157 SNR candidates, of which 80 are new. Polarization measurements provide evidence of nonthermal emission from 9 of these candidates. We find that two previously identified candidates are filaments. We also detect emission from 91 of the 94 known SNRs in the survey region. Four of these are reclassified as HII regions following detection in MIR surveys. The better sensitivity and resolution of the GLOSTAR data have led to the identification of 157 SNR candidates, along with the reclassification of several misidentified objects. We show that the polarization measurements can identify nonthermal emission, despite the diffuse Galactic synchrotron emission. These results underscore the importance of higher resolution and higher sensitivity radio continuum data in identifying and confirming SNRs.
82. GMVA 86GHz Stokes IQU images of 3C84 jet
ID:
ivo://CDS.VizieR/J/A+A/622/A196
Title:
GMVA 86GHz Stokes IQU images of 3C84 jet
Short Name:
J/A+A/622/A196
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report results from a deep polarization imaging of the nearby radio galaxy 3C 84 (NGC 1275). The source was observed with the Global Millimeter VLBI Array (GMVA) at 86GHz at an ultrahigh angular resolution of 50{mu}as (corresponding to 200Rs). We also add complementary multiwavelength data from the Very Long Baseline Array (VLBA; 15 & 43GHz) and from the Atacama Large Millimeter/submillimeter Array (ALMA; 97.5, 233.0, and 343.5GHz). At 86GHz, we measured a fractional linear polarization of ~2% in the VLBI core region. The polarization morphology suggests that the emission is associated with an underlying limb-brightened jet. The fractional linear polarization is lower at 43 and 15GHz (~0.3-0.7% and <0.1%, respectively). This suggests an increasing linear polarization degree toward shorter wavelengths on VLBI scales. We also obtain a large rotation measure (RM) of ~10^5-6^rad/m^2^ in the core at >~43GHz. Moreover, the VLBA 43GHz observations show a variable RM in the VLBI core region during a small flare in 2015. Faraday depolarization and Faraday conversion in an inhomogeneous and mildly relativistic plasma could explain the observed linear polarization characteristics and the previously measured frequency dependence of the circular polarization. Our Faraday depolarization modeling suggests that the RM most likely originates from an external screen with a highly uniform RM distribution. To explain the large RM value, the uniform RM distribution, and the RM variability, we suggest that the Faraday rotation is caused by a boundary layer in a transversely stratified jet. Based on the RM and the synchrotron spectrum of the core, we provide an estimate for the magnetic field strength and the electron density of the jet plasma.
83. G31.41+0.31 Stokes IQU images
ID:
ivo://CDS.VizieR/J/A+A/630/A54
Title:
G31.41+0.31 Stokes IQU images
Short Name:
J/A+A/630/A54
Date:
21 Oct 2021
Publisher:
CDS
Description:
Submillimeter Array (SMA) 870um polarization observations of the hot molecular core G31.41+0.31 revealed one of the clearest examples up to date of an hourglass-shaped magnetic field morphology in a high-mass star-forming region. To better establish the role that the magnetic field plays in the collapse of G31.41+0.31, we carried out Atacama Large Millimeter/submillimeter Array (ALMA) observations of the polarized dust continuum emission at 1.3mm with an angular resolution four times higher than that of the previous (sub)millimeter observations to achieve an unprecedented image of the magnetic field morphology. We used ALMA to perform full polarization observations at 233GHz (Band 6). The resulting synthesized beam is 00.28"x00.20" which, at the distance of the source, corresponds to a spatial resolution of 875au. The observations resolve the structure of the magnetic field in G31.41+0.31 and allow us to study the field in detail. The polarized emission in the Main core of G31.41+0.41 is successfully fit with a semi-analytical magnetostatic model of a toroid supported by magnetic fields. The best fit model suggests that the magnetic field is well represented by a poloidal field with a possible contribution of a toroidal component of 10% of the poloidal component, oriented southeast to northwest at ~-44{deg} and with an inclination of ~-45{deg}. The magnetic field is oriented perpendicular to the northeast to southwest velocity gradient detected in this core on scales from 10^3^-10^4^au. This supports the hypothesis that the velocity gradient is due to rotation of the core and suggests that such a rotation has little effect on the magnetic field. The strength of the magnetic field estimated in the central region of the core with the Davis-Chandrasekhar-Fermi method is ~8-13mG and implies that the mass-to-flux ratio in this region is slightly supercritical ({lambda}=1.4-2.2). The magnetic field in G31.41+0.31 maintains an hourglass-shaped morphology down to scales of <1000au. Despite the magnetic field being important in G31.41+0.31, it is not enough to prevent fragmentation and collapse of the core, as demonstrated by the presence of at least four sources embedded in the center of the core.
84. H-band images of IRAS 19312+1950
ID:
ivo://CDS.VizieR/J/A+A/470/957
Title:
H-band images of IRAS 19312+1950
Short Name:
J/A+A/470/957
Date:
21 Oct 2021
Publisher:
CDS
Description:
We obtained H-band polarimetric data of IRAS 19312+1950 using the near-infrared camera (CIAO) on the 8m Subaru telescope. In order to investigate the physical properties of the central star and the nebula, we performed dust radiative transfer modeling and compared the model results with the observed spectral energy distributions (SEDs), the radial profiles of the total intensity image, and the fraction of linear polarization map. The total intensity image shows a nearly spherical core with ~3" radius, an S-shaped arm extending ~10" in the northwest to southeast direction, and an extended lobe towards the southwest. The polarization map shows a centro-symmetric vector alignment in almost the entire nebula and low polarizations along the S-shaped arm. These results suggest that the nebula is accompanied by a central star, and the S-shaped arm has a physically ring-like structure. From our radiative transfer modeling, we estimated the stellar temperature, the bolometric luminosity, and the current mass-loss rate to be 2800K, 7000L_{sun}_, and 5.3x10^-6^M_{sun}_/yr, respectively. Taking into account previous observational results, such as the detection of SiO maser emissions and silicate absorption feature in the 10{mu}m spectrum, our dust radiative transfer analysis based on our NIR imaging polarimetry suggests that (1) the central star of IRAS 19312+1950 is likely to be an oxygen-rich, dust-enshrouded AGB star and (2) most of the circumstellar material originates from other sources (e.g. ambient dark clouds) rather than as a result of mass loss from the central star.
85. HD 117214 debris disk polarization images
ID:
ivo://CDS.VizieR/J/A+A/635/A19
Title:
HD 117214 debris disk polarization images
Short Name:
J/A+A/635/A19
Date:
21 Oct 2021
Publisher:
CDS
Description:
Young stars with debris disks are the most promising targets for an exoplanet search because debris indicate a successful formation of planetary bodies. Debris disks can be shaped by planets into ring structures that give valuable indications on the presence and location of planets in the disk. We performed observations of the Sco-Cen F star HD 117214 to search for planetary companions and to characterize the debris disk structure. HD 117214 was observed with the SPHERE subsystems IRDIS, IFS, and ZIMPOL at optical and near-IR wavelengths using angular and polarimetric differential imaging techniques. This provided the first images of scattered light from the debris disk with the highest spatial resolution of 25mas and an inner working angle <0.1". With the observations with IRDIS and IFS we derived detection limits for substellar companions. The geometrical parameters of the detected disk were constrained by fitting 3D models for the scattering of an optically thin dust disk. Investigating the possible origin of the disk gap, we introduced putative planets therein and modeled the planet-disk and planet-planet dynamical interactions. The obtained planetary architectures were compared with the detection limit curves. The debris disk has an axisymmetric ring structure with a radius of 0.42(+/-0.01)" or ~45au and an inclination of 71(+/-2.5){deg} and exhibits a 0.4" (~40au) wide inner cavity. From the polarimetric data, we derive a polarized flux contrast for the disk of (Fpol)_disk_/F*=(3.1+/-1.2)x10^-4^ in the RI band. The fractional scattered polarized flux of the disk is eight times lower than the fractional IR flux excess. This ratio is similar to the one obtained for the debris disk HIP 79977, indicating that dust radiation properties are similar for these two disks. Inside the disk cavity we achieve high-sensitivity limits on planetary companions with a mass down to ~4M_J_ at projected radial separations between 0.2" and 0.4". We can exclude stellar companions at a radial separation larger than 75mas from the star.
86. HD 172555 polarimetric images
ID:
ivo://CDS.VizieR/J/A+A/618/A151
Title:
HD 172555 polarimetric images
Short Name:
J/A+A/618/A151
Date:
21 Oct 2021
Publisher:
CDS
Description:
Debris disks or belts are important signposts for the presence of colliding planetesimals and, therefore, for ongoing planet formation and evolution processes in young planetary systems. Imaging of debris material at small separations from the star is very challenging but provides valuable insights into the spatial distribution of the so-called hot dust produced by solid bodies located in or near the habitable zone. We report the first detection of scattered light from the hot dust around the nearby (d=28.33pc) A star HD 172555. We want to constrain the geometric structure of the detected debris disk using polarimetric differential imaging (PDI) with a spatial resolution of 25mas and an inner working angle of about 0.1". We measured the polarized light of HD 172555, with SPHERE/ZIMPOL, in the very broadband (VBB) or RI filter ({lambda}c=735nm, {Delta}{lambda}290nm) for the projected separations between 0.08" (2.3au) and 0.77" (22au). We constrained the disk parameters by fitting models for scattering of an optically thin dust disk taking the limited spatial resolution and coronagraphic attenuation of our data into account. The geometric structure of the disk in polarized light shows roughly the same orientation and outer extent as obtained from thermal emission at 18{mu}m. Our image indicates the presence of a strongly inclined (i~=103.5{deg}), roughly axisymmetric dust belt with an outer radius in the range between 0.3" (8.5au) and 0.4" (11.3au). An inner disk edge is not detected in the data. We derive a lower limit for the polarized flux contrast ratio for the disk of (Fpol)disk/F*>(6.2+/-0.6)x10^-5^ in the VBB filter. This ratio is small, only ~9%, when compared to the fractional infrared flux excess (~=7.2x10^-4^). The model simulations show that more polarized light could be produced by the dust located inside ~=2au, which cannot be detected with the instrument configuration used. Our data confirm previous infrared imaging and provide a higher resolution map of the system, which could be further improved with future observations.
87. HD 139614 polarization Stokes Q and U images
ID:
ivo://CDS.VizieR/J/A+A/635/A121
Title:
HD 139614 polarization Stokes Q and U images
Short Name:
J/A+A/635/A121
Date:
21 Oct 2021
Publisher:
CDS
Description:
Shadows in scattered light images of protoplanetary disks are a common feature and support the presence of warps or misalignments between disk regions. These warps are possibly due to an inclined (sub-)stellar companion embedded in the disk. We study the morphology of the protoplanetary disk around the Herbig Ae star HD 139614 based on the first scattered light observations of this disk, which we model with the radiative transfer code MCMax3D. We obtained J- and H-band observations in polarized scattered light with VLT/SPHERE that show strong azimuthal asymmetries. In the outer disk, beyond ~30au, a broad shadow spans a range of ~240{deg} in position angle, in the East. A bright ring at ~16 au also shows an azimuthally asymmetric brightness, with the faintest side roughly coincidental with the brightest region of the outer disk. Additionally, two arcs are detected at ~34au and ~50au. We created a simple 4-zone approximation to a warped disk model of HD 139614 in order to qualitatively reproduce these features. The location and misalignment of the disk components were constrained from the shape and location of the shadows they cast. We find that the shadow on the outer disk covers a range of position angle too wide to be explained by a single inner misaligned component. Our model requires a minimum of two separate misaligned zones -- or a continuously warped region -- to cast this broad shadow on the outer disk. A small misalignment of ~4{deg} between adjacent components can reproduce most of the observed shadow features. Multiple misaligned disk zones, potentially mimicking a warp, can explain the observed broad shadows in the HD 139614 disk. A planetary mass companion in the disk, located on an inclined orbit, could be responsible for such a feature and for the dust depleted gap responsible for a dip in the SED.
88. HD61005 SPHERE H and Ks images
ID:
ivo://CDS.VizieR/J/A+A/591/A108
Title:
HD61005 SPHERE H and Ks images
Short Name:
J/A+A/591/A108
Date:
21 Oct 2021
Publisher:
CDS
Description:
Debris disks offer valuable insights into the latest stages of circumstellar disk evolution, and can possibly help us to trace the outcomes of planetary formation processes. In the age range 10 to 100Myr, most of the gas is expected to have been removed from the system, giant planets (if any) must have already been formed, and the formation of terrestrial planets may be on-going. Pluto-sized planetesimals, and their debris released in a collisional cascade, are under their mutual gravitational influence, which may result into non-axisymmetric structures in the debris disk. Here we present new VLT/SPHERE and ALMA observations of the debris disk around the 40Myr-old solar-type star HD61005. We resolve the disk at unprecedented resolution both in the near-infrared (in scattered and polarized light) and at millimeter wavelengths. We perform a detailed modeling of these observations, including the spectral energy distribution. Thanks to the new observations, we propose a solution for both the radial and azimuthal distribution of the dust grains in the debris disk. We find that the disk has a moderate eccentricity and that the dust density is two times larger at the pericenter compared to the apocenter. With no giant planets detected in our observations, we investigate alternative explanations besides planet-disk interactions to interpret the inferred disk morphology. We postulate that the morphology of the disk could be the consequence of a massive collision between 1000km-sized bodies at 61 au. If this interpretation holds, it would put stringent constraints on the formation of massive planetesimals at large distances from the star.
89. HD142527 SPHERE polarimetric images
ID:
ivo://CDS.VizieR/J/A+A/648/A110
Title:
HD142527 SPHERE polarimetric images
Short Name:
J/A+A/648/A110
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present high-precision photometry and polarimetry based on visual and near-infrared imaging data for the protoplanetary disk surrounding the Herbig Ae/Be star HD 142527, with a strong focus on determining the light scattering parameters of the dust located at the surface of the large outer disk. We re-reduced existing polarimetric differential imaging data of HD 142527 in the VBB (735nm) and H-band (1625nm) from the ZIMPOL and IRDIS subinstruments of SPHERE at the VLT. With polarimetry and photometry based on reference star differential imaging (RDI), we were able to measure the linearly polarized intensity and the total intensity of the light scattered by the circumstellar disk with high precision. We used simple Monte Carlo simulations of multiple light scattering by the disk surface to derive constraints for three scattering parameters of the dust: the maximum polarization of the scattered light Pmax, the asymmetry parameter g, and the single-scattering albedo {omega}. We measure a reflected total intensity of 51.4+/-1.5mJy and 206+/-12mJy and a polarized intensity of 11.3+/-0.3mJy and 55.1+/-3.3mJy in the VBB and H-band, respectively. We also find in the visual range a degree of polarization that varies between 28% on the far side of the disk and 17% on the near side. In the H-band, the degree of polarization is consistently higher by about a factor of 1.2. The disk also shows a red color for the scattered light intensity and the polarized intensity, which are about twice as high in the near-infrared when compared to the visual. We determine with model calculations the scattering properties of the dust particles and find evidence for strong forward scattering (g {prop.to} 0.5-0.75), relatively low single-scattering albedo ({omega} {prop.to} 0.2-0.5), and high maximum polarization (Pmax {prop.to} 0.5-0.75) at the surface on the far side of the disk for both observed wavelengths. The optical parameters indicate the presence of large aggregate dust particles, which are necessary to explain the high maximum polarization, the strong forward-scattering nature of the dust, and the observed red disk color.
90. High cadence polarization monitoring of OJ287
ID:
ivo://CDS.VizieR/J/A+A/619/A88
Title:
High cadence polarization monitoring of OJ287
Short Name:
J/A+A/619/A88
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a multifrequency, dense radio monitoring program of the blazar OJ287 using the 100-m Effelsberg radio telescope. The program aims to test different binary supermassive black hole (SMBH) scenarios and studying the physical conditions in the central region of this bright blazar. Between December 2015 and January 2017 (MJD 57370-57785), the radio electric vector position angle (EVPA) showed a large clockwise (CW) rotation by about 340{deg} with a mean rate of -1.04{deg}/day. Based on concurrent polarized Very Long Baseline Array (VLBA) data, the rotation seems to originate within the jet core at 43GHz. Optical polarization data show a similar monotonic CW EVPA rotation of about -1.1{deg}/day, superposed by shorter and faster rotations of about 7.8{deg}/day, mainly in the CW sense. When combined, the single dish, VLBI and optical polarization data are consistent with a polarized emission component propagating on a helical trajectory within a bent jet. We constrained the helix arc length (0.26pc) and radius (about 0.04pc) and the projected jet bending arc length (about 1.9-7.6pc). The helical trajectory covers only a part of the jet width, possibly its spine. In addition, we found a stable polarized component with EVPA (-10{deg}) perpendicular to the large scale jet, suggesting dominance of the poloidal magnetic field component.