- ID:
- ivo://CDS.VizieR/J/A+A/569/A81
- Title:
- CO observations towards W44E and W44F with APEX
- Short Name:
- J/A+A/569/A81
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- When supernova blast waves interact with nearby molecular clouds, they send slower shocks into these clouds. The resulting interaction regions provide excellent environments for the use of MHD shock models to constrain the physical and chemical conditions in these regions. The interaction of supernova remnants (SNRs) with molecular clouds gives rise to strong molecular emission in the far-IR and sub-mm wavelength regimes. The application of MHD shock models in the interpretation of this line emission can yield valuable information on the energetic and chemical impact of supernova remnants. New mapping observations with the APEX telescope in ^12^CO (3-2), (4-3), (6-5), (7-6) and ^13^CO (3-2) towards two regions in the supernova remnant W44 are presented. Integrated intensities are extracted on five different positions, corresponding to local maxima of CO emission. The integrated intensities are compared to the outputs of a grid of models, which combine an MHD shock code with a radiative transfer module based on the 'large velocity gradient' approximation. Results: All extracted spectra show ambient and line-of-sight components as well as blue- and red-shifted wings indicating the presence of shocked gas. Basing the shock model fits only on the highest-lying transitions that unambiguously trace the shock-heated gas, we find that the observed CO line emission is compatible with non-stationary shocks and a pre-shock density of 10^4^cm^-3^. The ages of the modelled shocks scatter between values of ~1000 and ~3000 years. The shock velocities in W44F are found to lie between 20 and 25km/s, while in W44E fast shocks (30-35km/s) as well as slower shocks (~20km/s) are compatible with the observed spectral line energy diagrams. The pre-shock magnetic field strength components perpendicular to the line-of-sight in both regions have values between 100 and 200uG. Our best-fitting models allow us to predict the full ladder of CO transitions, the shocked gas mass in one beam as well as the momentum- and energy injection.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/391/1384
- Title:
- Deep MERLIN 5GHz radio sources in M82
- Short Name:
- J/MNRAS/391/1384
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of an extremely deep, 8-d long observation of the central kpc of the nearby starburst galaxy M82 using Multi-Element Radio Linked Interferometer Network (MERLIN) at 5GHz are presented. The 17{mu}Jy/beam rms noise level in the naturally weighted image makes it the most sensitive high-resolution radio image of M82 made to date. Over 50 discrete sources are detected, the majority of which are supernova remnants, but with 13 identified as H ii regions. Sizes, flux densities and radio brightnesses are given for all of the detected sources, which are all well resolved with a majority showing shell or partial shell structures. Those sources within the sample which are supernova remnants have diameters ranging from 0.3 to 6.7pc, with a mean size of 2.9pc.
- ID:
- ivo://CDS.VizieR/J/MNRAS/490/5063
- Title:
- Extended sources in SCORPIO at 2.1GHz
- Short Name:
- J/MNRAS/490/5063
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalogue of a large sample of extended radio sources in the Stellar Continuum Originating from Radio Physics In Ourgalaxy (SCORPIO) field, observed and resolved by the Australia Telescope Compact Array. SCORPIO, a pathfinder project for addressing the early operations of the Australia SKA Pathfinder, is a survey of ~5 square degrees between 1.4 and 3.1GHz, centred at l=343.5{deg}, b=0.75{deg}, and with an angular resolution of about 10 arcsec. It is aimed at understanding the scientific and technical challenges to be faced by future Galactic surveys. With a mean sensitivity around 100uJy/beam and the possibility to recover angular scales at least up to 4 arcmin, we extracted 99 extended sources, 35 of them detected for the first time. Among the 64 known sources 55 had at least a tentative classification in literature. Studying the radio morphology and comparing the radio emission with infrared we propose as candidates six new HII regions, two new planetary nebulae, two new luminous blue variable or Wolf-Rayet stars, and three new supernova remnants. This study provides an overview of the potentiality of future radio surveys in terms of Galactic source extraction and characterization and a discussion on the difficulty to reduce and analyse interferometric data on the Galactic plane.
- ID:
- ivo://CDS.VizieR/J/ApJS/217/4
- Title:
- 2FGL sources observed between 5-9GHz
- Short Name:
- J/ApJS/217/4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of an all-sky radio survey between 5 and 9GHz of sky areas surrounding all unassociated {gamma}-ray objects listed in the Fermi Large Area Telescope Second Source Catalog (2FGL). The goal of these observations is to find all new {gamma}-ray active galactic nucleus (AGN) associations with radio sources >10mJy at 8GHz. We observed with the Very Large Array and the Australia Telescope Compact Array the areas around unassociated sources, providing localizations of weak radio point sources found in 2FGL fields at arcmin scales. Then we followed-up a subset of those with the Very Long Baseline and the Long Baseline Arrays to confirm detections of radio emission on parsec-scales. We quantified association probabilities based on known statistics of source counts and assuming a uniform distribution of background sources. In total we found 865 radio sources at arcsec scales as candidates for association and detected 95 of 170 selected for follow-up observations at milliarcsecond resolution. Based on this we obtained firm associations for 76 previously unknown {gamma}-ray AGNs. Comparison of these new AGN associations with the predictions from using the Wide-field Infrared Survey Explorer color-color diagram shows that half of the associations are missed. We found that 129 out of 588 observed {gamma}-ray sources at arcmin scales not a single radio continuum source was detected above our sensitivity limit within the 3{sigma} {gamma}-ray localization. These "empty" fields were found to be particularly concentrated at low Galactic latitudes. The nature of these Galactic {gamma}-ray emitters is not yet determined.
- ID:
- ivo://CDS.VizieR/J/A+A/641/A121
- Title:
- G203.7+11.5 21cm and 11cm intensity maps
- Short Name:
- J/A+A/641/A121
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In soft X-rays, the Monogem ring is an object with a diameter of 25{deg} located in the Galactic anti-centre. It is believed to be a faint, evolved, local supernova remnant. It is not seen at radio wavelengths, as other large supernova remnants are. We study a narrow about 4.5D long, faint Halpha-filament, G203.7+11.5, that is seen towards the centre of the Monogem ring. It causes depolarisation and excessive Faraday rotation of radio polarisation data. Polarisation observations at 11cm and 21cm with the Effelsberg 100-m telescope were analysed.
- 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.
- ID:
- ivo://CDS.VizieR/J/ApJ/839/83
- Title:
- GMOS spectroscopic obs. of SNR candidates in M83
- Short Name:
- J/ApJ/839/83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results from a spectrophotometric study sampling the 300 candidate supernova remnants (SNRs) in M83 identified through optical imaging with Magellan/IMACS and Hubble Space Telescope/WFC3. Of the 118 candidates identified based on a high [SII]{lambda}{lambda}6716,6731 to H{alpha} emission ratio, 117 show spectroscopic signatures of shock-heated gas, confirming them as SNRs-the largest uniform set of SNR spectra for any galaxy. Spectra of 22 objects with a high [OIII]{lambda}5007 to H{alpha} emission ratio, selected in an attempt to identify young ejecta-dominated SNRs like Cas A, reveal only one (previously reported) object with the broad (1000km/s) emission lines characteristic of ejecta-dominated SNRs, beyond the known SN1957D remnant. The other 20 [OIII]-selected candidates include planetary nebulae, compact HII regions, and one background QSO. Although our spectroscopic sample includes 22 SNRs smaller than 11pc, none of the other objects show broad emission lines; instead their spectra stem from relatively slow (~200km/s) radiative shocks propagating into the metal-rich interstellar medium of M83. With six SNe in the past century, one might expect more of M83's small-diameter SNRs to show evidence of ejecta; this appears not to be the case. We attribute their absence to several factors, including that SNRs expanding into a dense medium evolve quickly to the ISM-dominated phase, and that SNRs expanding into regions already evacuated by earlier SNe are probably very faint.
- ID:
- ivo://CDS.VizieR/J/A+A/612/A3
- Title:
- HESS Galactic supernova remnants
- Short Name:
- J/A+A/612/A3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Shell-type supernova remnants (SNRs) are considered prime candidates for the acceleration of Galactic cosmic rays (CRs) up to the knee of the CR spectrum at E~=3x10^15^eV. Our Milky Way galaxy hosts more than 350 SNRs discovered at radio wavelengths and at high energies, of which 220 fall into the H.E.S.S. Galactic Plane Survey (HGPS) region. Of those, only 50 SNRs are coincident with a H.E.S.S source and in 8 cases the very high-energy (VHE) emission is firmly identified as an SNR. The H.E.S.S. GPS provides us with a legacy for SNR population study in VHE {gamma}-rays and we use this rich data set to extract VHE flux upper limits from all undetected SNRs. Overall, the derived flux upper limits are not in contradiction with the canonical CR paradigm. Assuming this paradigm holds true, we can constrain typical ambient density values around shell-type SNRs to n<=7cm^-3^ and electron-to-proton energy fractions above 10TeV to {epsilon}_ep_<=5x10^-3^. Furthermore, comparisons of VHE with radio luminosities in non-interacting SNRs reveal a behaviour that is in agreement with the theory of magnetic field amplification at shell-type SNRs.
- ID:
- ivo://CDS.VizieR/J/A+A/651/A9
- Title:
- HIFI molecular line survey of SgrB2 (M)
- Short Name:
- J/A+A/651/A9
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- We present a full analysis of a broadband spectral line survey of Sagittarius B2 (Main), one of the most chemically rich regions in the Galaxy located within the giant molecular cloud complex Sgr B2 in the Central Molecular Zone. Our goal is to derive the molecular abundances and temperatures of the high-mass star-forming region Sgr B2(M) and thus its physical and astrochemical conditions. Sgr B2(M) was observed using the Heterodyne Instrument for the Far-Infrared (HIFI) on board the Herschel Space Observatory in a spectral line survey from 480 to 1907GHz at a spectral resolution of 1.1MHz, which provides one of the largest spectral coverages ever obtained toward this high-mass star-forming region in the submillimeter with high spectral resolution and includes frequencies >1THz that are unobservable from the ground. We modeled the molecular emission from the submillimeter to the far-infrared using the XCLASS program, which assumes local thermodynamic equilibrium (LTE). For each molecule, a quantitative description was determined taking all emission and absorption features of that species across the entire spectral range into account. Because of the wide frequency coverage, our models are constrained by transitions over an unprecedented range in excitation energy. Additionally, we derived velocity resolved ortho/para ratios for those molecules for which ortho and para resolved molecular parameters are available. Finally, the temperature and velocity distributions are analyzed and the derived abundances are compared with those obtained for Sgr B2(N) from a similar HIFI survey. A total of 92 isotopologues were identified, arising from 49 different molecules, ranging from free ions to complex organic compounds and originating from a variety of environments from the cold envelope to hot and dense gas within the cores. Sulfur dioxide, methanol, and water are the dominant contributors. Vibrationally excited HCN (v2=1) and HNC (v2=1) are detected as well. For the ortho/para ratios, we find deviations from the high temperature values between 37 and 180%. In total 14% of all lines remain unidentified. Compared to Sgr B2(N), we found less complex molecules such as CH_3_OCH_3_, CH_3_NH_2_, or NH_2_CHO, but more simple molecules such as CN, CCH, SO, and SO_2_. However some sulfur bearing molecules such as H_2_CS, CS, NS, and OCS are more abundant in N than in M. The derived molecular abundances can be used for comparison to other sources and for providing further constraints for astrochemical models.
- ID:
- ivo://CDS.VizieR/J/A+A/466/989
- Title:
- Hot ammonia from NGC 6334I and NGC 6334I(N)
- Short Name:
- J/A+A/466/989
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The massive twin cores NGC 6334I and I(N) are in different evolutionary stages and hence ideal targets to study evolutionary variations within the same larger-scale environment. Here, we study the warm, compact gas components. We imaged the two regions with the Australia Telescope Compact Array (ATCA) at high angular resolution in the NH3(3, 3) to (6, 6) inversion lines.
