- ID:
- ivo://CDS.VizieR/J/ApJ/899/14
- Title:
- Optical & FeII sources in Supernova remnant with HST
- Short Name:
- J/ApJ/899/14
- Date:
- 14 Mar 2022 07:07:21
- Publisher:
- CDS
- Description:
- NGC6946 is a high-star-formation-rate, face-on, spiral galaxy that has hosted 10 supernovae since 1917. Not surprisingly, a large number of supernova remnants and candidates have been identified either as optical nebulae with high [SII]:H{alpha} line ratios (147) or as compact non-thermal radio sources (35). However, there are only seven overlaps between these two samples. Here, we apply [FeII] 1.644{mu}m emission as a new diagnostic to search for supernova remnants in an attempt to resolve this discrepancy. [FeII] is expected to be relatively strong in the radiative shocks of supernova remnants and almost absent in HII regions. It is less susceptible to the effects of absorption along the line of sight than the optical lines normally used to identify remnants. Using data from the WFC3 camera on Hubble Space Telescope (HST), we identify 132 [FeII] emission nebulae in NGC6946 as likely supernova remnants. Of these, 54 align with previously known optical supernova remnants. The remaining 78 objects are new; of these 44 are visible in new HST imagery in H{alpha} and [SII]. This brings the total number of supernova remnant candidates (from optical and/or IR data) in NGC6946 to 225. A total of 14 coincidences with radio supernova remnant candidates (out of 30 in our search area) are found in this expanded list. The identification of so many new remnant candidates validates the use of [FeII] imagery for finding remnants, and suggests that previous remnant searches in other galaxies may be far from complete.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJS/174/379
- Title:
- Optical imaging and spectra of 3C 58
- Short Name:
- J/ApJS/174/379
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a comprehensive imaging and spectroscopic survey of optical emission knots associated with the young Galactic supernova remnant 3C 58. H{alpha} images show hundreds of clumpy filaments and knots arranged in a complex structure covering a nearly circular area roughly 400" in diameter. A quite different emission structure is seen in [OIII], where the brightest features are less clumpy and largely confined to the remnant's northwest quadrant. Measured radial velocities of over 450 knots reveal two distinct kinematic populations; one with average and peak expansion velocities of 770 and 1100km/s, respectively, forming a thick shell, and the other showing |v|<=250km/s. High-velocity knots (|v|>=500km/s) exhibit a strong bipolar expansion pattern with redshifted and blueshifted knots located in northeastern and southwestern regions, respectively. These knots also show strong [NII]/H{alpha} line emission ratios, suggesting enhanced N/H. In contrast, the slower expanding knot population shows much lower [NII]/H{alpha} line ratios and likely represents circumstellar mass loss material from the 3C 58 progenitor. Proper-motion estimates using images spanning a 28yr time interval suggest positional shifts of between 0.5" and 2.0", implying proper motions of 0.02-0.07"/yr. These values agree with previous estimates but are much less than the ~0.2"/yr expected if 3C 58 were associated with historic guest star of 1181 CE.
- ID:
- ivo://CDS.VizieR/J/AJ/130/1345
- Title:
- Optical-infrared colors of CORALS QSOs
- Short Name:
- J/AJ/130/1345
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The presence of dust in quasar absorbers, such as damped Ly{alpha} (DLA) systems, may cause the background QSO to appear reddened. We investigate the extent of this potential reddening by comparing the optical-to-infrared colors of QSOs with and without intervening absorbers. Our QSO sample is based on the Complete Optical and Radio Absorption Line System (CORALS) survey of Ellison and coworkers. The CORALS data set consists of 66 radio-selected QSOs at z_em_>=2.2 with complete optical identifications. We have obtained near-simultaneous B- and K-band magnitudes for a subset of the CORALS sample and supplemented our observations with further measurements published in the literature. In total, we have B-K colors for 42 of the 66 QSOs, of which 14 have intervening DLA systems. To account for redshift-related color changes, the B-K colors are normalized using the Sloan Digital Sky Survey QSO composite.
- ID:
- ivo://CDS.VizieR/J/ApJ/728/104
- Title:
- Optical polarization for 878 Hipparcos stars
- Short Name:
- J/ApJ/728/104
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Sun is located inside an extremely low density and quite irregular volume of the interstellar medium, known as the Local Cavity (LC). It has been widely believed that some kind of interaction could be occurring between the LC and Loop I, a nearby superbubble seen in the direction of the Galactic center. As a result of such interaction, a wall of neutral and dense material, surrounded by a ring-shaped feature, would be formed at the interaction zone. Evidence of this structure was previously observed by analyzing the soft X-ray emission in the direction of Loop I. Our goal is to investigate the distance of the proposed annular region and map the geometry of the Galactic magnetic field in these directions. On that account, we have conducted an optical polarization survey of 878 stars from the Hipparcos catalog. Our results suggest that the structure is highly twisted and fragmented, showing very discrepant distances along the annular region: ~100pc on the left side and 250pc on the right side, independently confirming the indication from a previous photometric analysis. In addition, the polarization vectors' orientation pattern along the ring also shows a widely different behavior toward both sides of the studied feature, running parallel to the ring contour on the left side and showing no relation to its direction on the right side. Altogether, these evidences suggest a highly irregular nature, casting some doubt on the existence of a unique large-scale ring-like structure.
- ID:
- ivo://CDS.VizieR/J/A+AS/101/551
- Title:
- Optical polarization of 1000 stars
- Short Name:
- J/A+AS/101/551
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have prepared a catalogue of optical polarization measurements for 1000 stars closer than 50 parsecs from the Sun. The distances, which are presently those given in the Sky Catalogue 2000.0, 2nd Edition (Hirshfeld et al., 1991skca.book.....H) are provisional: they will be replaced later by the much safer parallaxes which will result from the Hipparcos mission. The polarization data have been compiled, for 60% in various catalogues with due care to their accuracy; for 40% they are new, unpublished, measurements obtained at Pic du Midi Observatory. We expect that this new data base will allow a better understanding of the interstellar medium around the Sun.
- ID:
- ivo://CDS.VizieR/J/MNRAS/452/715
- Title:
- Optical polarization of the Polaris Flare
- Short Name:
- J/MNRAS/452/715
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The stages before the formation of stars in molecular clouds are poorly understood. Insights can be gained by studying the properties of quiescent clouds, such as their magnetic field structure. The plane-of-the-sky orientation of the field can be traced by polarized starlight. We present the first extended, wide-field (~10deg^2^) map of the Polaris Flare cloud in dust-absorption induced optical polarization of background stars, using the Robotic Polarimeter (RoboPol) polarimeter at the Skinakas Observatory. This is the first application of the wide-field imaging capabilities of RoboPol. The data were taken in the R band and analysed with the automated reduction pipeline of the instrument. We present in detail optimizations in the reduction pipeline specific to wide-field observations. Our analysis resulted in reliable measurements of 641 stars with median fractional linear polarization 1.3%. The projected magnetic field shows a large-scale ordered pattern. At high longitudes it appears to align with faint striations seen in the Herschel-Spectral and Photometric Imaging Receiver (SPIRE) map of dust emission (250um), while in the central 4.5 deg2 it shows an eddy-like feature. The overall polarization pattern we obtain is in good agreement with large-scale measurements by Planck of the dust emission polarization in the same area of the sky.
- ID:
- ivo://CDS.VizieR/J/ApJS/151/313
- Title:
- Optical spectra in star-forming regions
- Short Name:
- J/ApJS/151/313
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present high-resolution optical spectra (at ~0.6-1.8km/s) of interstellar CN, CH, CH+, CaI, KI, and CaII absorption toward 29 lines of sight in three star-forming regions, {rho} Oph, Cep OB2, and Cep OB3. The observations and data reduction are described. The agreement between earlier measurements of the total equivalent widths and our results is quite good. However, our higher resolution spectra reveal complex structure and closely blended components in most lines of sight. The velocity component structure of each species is obtained by analyzing the spectra of the six species for a given sight line together. The tabulated column densities and Doppler parameters of individual components are determined by using the method of profile fitting. Total column densities along lines of sight are computed by summing results from profile fitting for individual components and are compared with column densities from the apparent optical depth method. A more detailed analysis of these data and their implications will be presented in a companion paper.
- ID:
- ivo://CDS.VizieR/J/ApJ/844/138
- Title:
- Optical spectroscopy toward Orion B fields
- Short Name:
- J/ApJ/844/138
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from high-resolution optical spectra toward 66 young stars in the Orion B molecular cloud to study their kinematics and other properties. Observations of the H{alpha} and Li I 6707{AA} lines are used to check membership and accretion properties. While the stellar radial velocities of NGC 2068 and L1622 are in good agreement with that of the molecular gas, many of the stars in NGC 2024 show a considerable offset. This could be a signature of either the expansion of the cluster, the high degree of the ejection of the stars from the cluster through dynamical interaction, or the acceleration of the gas due to stellar feedback.
- ID:
- ivo://CDS.VizieR/J/ApJS/217/7
- Title:
- Orion A dense cores based on 1.1mm and C^18^O
- Short Name:
- J/ApJS/217/7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Orion A giant molecular cloud core catalogs, which are based on a 1.1mm map with an angular resolution of 36" (~0.07pc) and C^18^O (J=1-0) data with an angular resolution of 26.4" (~0.05pc). We have cataloged 619 dust cores in the 1.1mm map using the Clumpfind method. The ranges of the radius, mass, and density of these cores are estimated to be 0.01-0.20pc, 0.6-1.2x10^2^M_{sun}_ , and 0.3x10^4^-9.2x10^6^cm^-3^, respectively. We have identified 235 cores from the C^18^O data. The ranges of the radius, velocity width, LTE mass, and density are 0.13-0.34pc, 0.31-1.31km/s, 1.0-61.8M_{sun}_ , and (0.8-17.5)x10^3^cm^-3^, respectively. From the comparison of the spatial distributions between the dust and C^18^O cores, four types of spatial relations were revealed: (1) the peak positions of the dust and C^18^O cores agree with each other (32.4% of the C^18^O cores), (2) two or more C^18^O cores are distributed around the peak position of one dust core (10.8% of the C^18^O cores), (3) 56.8% of the C^18^O cores are not associated with any dust cores, and (4) 69.3% of the dust cores are not associated with any C^18^O cores.
- ID:
- ivo://CDS.VizieR/J/A+A/564/A68
- Title:
- Orion A GMC 13CO and C18O maps
- Short Name:
- J/A+A/564/A68
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We derive physical properties such as the optical depths and the column densities of ^13^CO and C^18^O to investigate the relationship between the far ultraviolet (FUV) radiation and the abundance ratios between ^13^CO and C^18^O.
