- ID:
- ivo://CDS.VizieR/J/MNRAS/507/2885
- Title:
- Radio continuum sources behind LMC
- Short Name:
- J/MNRAS/507/2885
- Date:
- 07 Feb 2022 08:00:21
- Publisher:
- CDS
- Description:
- We present a comprehensive multifrequency catalogue of radio sources behind the Large Magellanic Cloud (LMC) between 0.2 and 20GHz, gathered from a combination of new and legacy radio continuum surveys. This catalogue covers an area of ~144deg^2^ at angular resolutions from 45 arcsec to ~3 arcmin. We find 6434 discrete radio sources in total, of which 3789 are detected at two or more radio frequencies. We estimate the median spectral index ({alpha}; where S_v_~{nu}^{alpha}^) of {alpha}=-0.89 and mean of -0.88+/-0.48 for 3636 sources detected exclusively at two frequencies (0.843 and 1.384GHz) with similar resolution [full width at half-maximum (FWHM) ~40-45 arcsec]. The large frequency range of the surveys makes it an effective tool to investigate Gigahertz Peak Spectrum (GPS), Compact Steep Spectrum (CSS), and Infrared Faint Radio Source (IFRS) populations within our sample. We find 10 GPS candidates with peak frequencies near 5GHz, from which we estimate their linear size. 1866 sources from our catalogue are CSS candidates with {alpha}<-0.8. We found six candidates for High Frequency Peaker (HFP) sources, whose radio fluxes peak above 5GHz and no sources with unconstrained peaks and {alpha}>0.5. We found optical counterparts for 343 of the radio continuum sources, of which 128 have a redshift measurement. Finally, we investigate the population of 123 IFRSs found in this study.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+AS/111/311
- Title:
- Radio continuum study of the MC
- Short Name:
- J/A+AS/111/311
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- From observations with the Parkes radio telescope, we present catalogues of radio sources in the Large Magellanic Cloud at four frequencies: 1.40, 2.45, 4.75 and 8.55GHz, and an additional catalogue from a source analysis of the Parkes-MIT-NRAO survey at 4.85GHz. A total of 469 sources have been detected at least one of these frequencies, 132 of which are reported here for the first time as radio sources.
- ID:
- ivo://CDS.VizieR/J/A+AS/127/119
- Title:
- Radio continuum study of the MC
- Short Name:
- J/A+AS/127/119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- By comparing Parkes telescope radio surveys with the X-ray ROSAT All-Sky Survey (RASS) we have found 71 discrete sources of both radio and X-ray emission in the Large Magellanic Cloud (LMC). These 71 sources are mainly supernova remnants (SNRs) and SNR candidates (36), and background sources (27). For six of the sources we have no proposed identification and the other two are HII regions. A source-intensity comparison of the radio and X-ray sources shows very little correlation, but we note that the strongest SNRs at both radio and X-ray frequencies are young SNRs from Population I. Six new LMC SNR candidates are proposed. From the radio flux density of the SNRs we have estimated the SNR birth rate to be one every 100 (+/-20) yr and the star-formation rate (SFR) to be 0.7 (+/-0.2)M_{sun}_/yr. A similar comparison was undertaken for the Small Magellanic Cloud (SMC), but instead of the RASS we used a roster of pointed observations made with the ROSAT Position Sensitive Proportional Counter (PSPC). This comparison resulted in 27 sources in common between the Parkes radio and ROSAT PSPC surveys. Two new SMC sources are proposed for SNR candidates. The SMC SNR birth rate was estimated to be one every 350 (+/-70)yr and the SFR was estimated to be 0.15 (+/-0.05)M_{sun}_/yr.
- ID:
- ivo://CDS.VizieR/J/A+AS/130/421
- Title:
- Radio continuum study of the MC
- Short Name:
- J/A+AS/130/421
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of discrete radio sources in the Magellanic Clouds (MCs) using the latest large-scale radio surveys made with the Parkes radio telescope between 1.4 and 8.55GHz. These surveys achieved higher sensitivity than previous surveys done with the Parkes telescope and so the number of discrete radio sources detected towards the MCs has increased by factor of five. Also, we have obtained improved positions, flux densities and radio spectral indices for all of these sources. A total of 483 sources towards the Large Magellanic Cloud (LMC) and 224 towards the Small Magellanic Cloud (SMC) have been detected at at least one radio frequency. Most of the MC's sources have been classified in one of three groups: SNRs, HII regions or background sources according to classification criteria established here. In total, 209 discrete radio sources in the LMC and the 37 sources in the SMC are classified here to be either HII regions or SNRs. We investigate their luminosity functions as well as the statistics of background sources behind the MCs. Also, we examine the distribution of SNRs and HII regions in the MCs.
- ID:
- ivo://CDS.VizieR/J/A+AS/120/77
- Title:
- Radio continuum study of the MC
- Short Name:
- J/A+AS/120/77
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new catalogue of radio sources in the Large Magellanic Cloud (LMC) based on observations at 2.30GHz with the Parkes radio telescope. A total of 119 sources have been detected. We compare positions and flux densities of these sources with previously published radio results and find no significant positional displacement or flux discrepancies.
- ID:
- ivo://CDS.VizieR/J/MNRAS/298/692
- Title:
- Radio Survey of X-ray sources
- Short Name:
- J/MNRAS/298/692
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a radio survey of X-ray sources in the Large and Small Magellanic clouds with the Australia Telescope Compact Array at 6.3 and 3.5 cm. Specifically, we have observed the fields of five LMC and two SMC supersoft X-ray sources, the X-ray binaries LMC X-1, X-2, X-3 & X-4, the X-ray transient Nova SMC 1992, and the soft gamma-ray repeater SGR 0525-66. None of the targets are detected as point sources at their catalogued positions. In particular, the proposed supersoft jet source RXJ 0513-69 is not detected, placing constraints on its radio luminosity compared to Galactic jet sources. Limits on emission from the black hole candidate systems LMC X-1 and X-3 are consistent with the radio behaviour of persistent Galactic black hole X-ray binaries, and a previous possible radio detection of LMC X-1 is found to almost certainly be due to nearby field sources. The SNR N49 in the field of SGR 0525-66 is mapped at higher resolution than previously, but there is still no evidence for any enhanced emission or disruption of the SNR at the location of the X-ray source. No radio point sources were detected at any wavelength at the catalogued locations of the target sources. In most cases a noise level of 50 microJy or so was achieved, making the 3-sigma upper limits very stringent indeed. The noise levels for LMC X-1 and SGR 0525-66 are considerably worse, due to their locations in radio-bright regions.
- ID:
- ivo://CDS.VizieR/J/A+A/430/421
- Title:
- Reddening in LMC bar region
- Short Name:
- J/A+A/430/421
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- E(V-I) reddening values for 1123 locations in the bar region of the Large Magellanic Cloud are presented. V, I photometry of red clump stars identified in the Optical Gravitational Lensing Experiment II (OGLE-II) catalogue of LMC were used to estimate reddening. E(V-I) values were estimated as the difference between observed and the characteristic values of (V-I) for the red clump population in a given region. It is found that most of the regions in the bar have reddening values less than 0.1mag with only a few locations having values more than 0.2mag. The eastern side of the bar is found to be more reddened when compared to the western side, with similar and relatively small values for differential reddening as in most parts of the bar. Increased reddening in the eastern end of the bar could be caused by a small fraction of the H I clouds in the line of sight. A high density of HI clouds located in the eastern end of the bar should have caused very high reddening in these regions, whereas only a relatively small increase in the reddening is estimated. This indicates that most of the H I clouds in this direction are likely to be located behind the bar.
- ID:
- ivo://CDS.VizieR/J/MNRAS/442/1680
- Title:
- Red giants in SMC. Abundances
- Short Name:
- J/MNRAS/442/1680
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from the largest Caii triplet line metallicity study of Small Magellanic Cloud (SMC) field red giant stars to date, involving 3037 objects spread across approximately 37.5deg^2^, centred on this galaxy. We find a median metallicity of [Fe/H]=-0.99+/-0.01, with clear evidence for an abundance gradient of -0.075+/-0.011dex/deg over the inner 5{deg}. We interpret the abundance gradient to be the result of an increasing fraction of young stars with decreasing galactocentric radius, coupled with a uniform global age-metallicity relation. We also demonstrate that the age-metallicity relation for an intermediate-age population located 10kpc in front of the north-east of the cloud is indistinguishable from that of the main body of the galaxy, supporting a prior conjecture that this is a stellar analogue of the Magellanic Bridge. The metal-poor and metal-rich quartiles of our red giant branch star sample (with complementary optical photometry from the Magellanic Clouds Photometric Survey) are predominantly older and younger than approximately 6Gyr, respectively. Consequently, we draw a link between a kinematical signature, tentatively associated by us with a disc-like structure, and the upsurges in stellar genesis imprinted on the star formation history of the central regions of the SMC. We conclude that the increase in the star formation rate around 5-6Gyr ago was most likely triggered by an interaction between the SMC and Large Magellanic Cloud.
- ID:
- ivo://CDS.VizieR/J/AJ/153/261
- Title:
- Red giant stellar parameters in the LMC bar
- Short Name:
- J/AJ/153/261
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report new spectroscopic observations obtained with the Michigan/Magellan Fiber System of 308 red giants (RGs) located in two fields near the photometric center of the bar of the Large Magellanic Cloud. This sample consists of 131 stars observed in previous studies (in one field) and 177 newly observed stars (in the second field) selected specifically to more reliably establish the metallicity and age distributions of the bar. For each star, we measure its heliocentric line-of-sight velocity, surface gravity, and metallicity from its high-resolution spectrum (effective temperatures come from photometric colors). The spectroscopic Hertzsprung-Russell diagrams- modulo small offsets in surface gravities-reveal good agreement with model isochrones. The mean metallicity of the 177-RG sample is [Fe/H]=-0.76+/-0.02 with a metallicity dispersion {sigma}=0.28+/-0.03. The corresponding metallicity distribution-corrected for selection effects-is well fitted by two Gaussian components: one metal-rich with a mean -0.66+/-0.02 and a standard deviation 0.17+/-0.01, and the other metal-poor with -1.20+/-0.24 and 0.41+/-0.06. The metal-rich and metal-poor populations contain approximately 85% and 15% of stars, respectively. We also confirm that the velocity dispersion in the bar center decreases significantly from 31.2+/-4.3 to 18.7+/-1.9km/s with increasing metallicity over the range -2.09 to -0.38. Individual stellar masses are estimated using the spectroscopic surface gravities and the known luminosities. We find that lower mass, hence older, RGs have larger metallicity dispersion and lower mean metallicity than the higher-mass, younger RGs. The estimated masses, however, extend to implausibly low values (~0.1M_{sun}_), making it impossible to obtain an absolute age-metallicity or age distribution of the bar.
- ID:
- ivo://CDS.VizieR/J/AJ/126/2867
- Title:
- Red supergiants in Magellanic Clouds
- Short Name:
- J/AJ/126/2867
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the red supergiant (RSG) content of the SMC and LMC using multiobject spectroscopy on a sample of red stars previously identified by BVR CCD photometry. We obtained high-accuracy (<1km/s) radial velocities for 118 red stars seen toward the SMC and 167 red stars seen toward the LMC, confirming most of these (89% and 95%, respectively) as red supergiants. Spectral types were also determined for most of these RSGs.
