- ID:
- ivo://CDS.VizieR/J/MNRAS/363/405
- Title:
- SIMBA observations of cold cores
- Short Name:
- J/MNRAS/363/405
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results of a 1.2-mm continuum emission survey toward 131 star-forming complexes suspected of undergoing massive star formation. These regions have previously been identified as harbouring a methanol maser and/or a radio continuum source [ultracompact (UC) HII region], the presence of which is in most instances indicative of massive star formation. The 1.2-mm emission was mapped using the SIMBA instrument on the 15-m Swedish ESO Submillimetre Telescope (SEST). Emission is detected toward all of the methanol maser and UC HII regions targeted, as well as towards 20 others lying within the fields mapped, implying that these objects are associated with cold, deeply embedded objects. Interestingly, there are also 20 methanol maser sites and nine UC HII regions within the fields mapped which are devoid of millimetre continuum emission. In addition to the maser and UC HII regions detected, we have also identified 253 other sources within the SIMBA maps. All of these (253) are new sources, detected solely from their millimetre continuum emission. In total, 404 sources are detected, representing four classes of sources which are distinguished by the presence of the different combination of associated tracers.
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- ID:
- ivo://CDS.VizieR/J/A+A/471/103
- Title:
- SIMBA observations of SMC
- Short Name:
- J/A+A/471/103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CO observations have been the best way so far to trace molecular gas in external galaxies, but in low metallicity environments the gas mass deduced could be largely underestimated due to enhanced photodissociation of the CO molecule. Large envelopes of H_2_ could therefore be missed by CO observations. At present, the kinematic information of CO data cubes are used to estimate virial masses and trace the total mass of the molecular clouds. Millimeter dust emission can also be used as a dense gas tracer and could unveil H_2_ envelopes lacking CO. These different tracers must be compared in different environments. This study compares virial masses to masses deduced from millimeter emission, in two GMC samples: the local molecular clouds in our Galaxy (10^4^-10^5^M_{sun}_), and their equivalents in the Small Magellanic Cloud (SMC), one of the nearest low metallicity dwarf galaxies. In our Galaxy, mass estimates deduced from millimeter (FIRAS) emission are consistent with masses deduced from gamma ray analysis and therefore trace the total mass of the clouds. Virial masses are systematically larger (twice on average) than mass estimates from millimeter dust emission. This difference decreases toward high masses and has been reported in previous studies. This is not the case for SMC giant molecular clouds: molecular cloud masses deduced from SIMBA millimeter observations are systematically higher (twice on average for conservative values of the dust to gas ratio and dust emissivity) than the virial masses from SEST CO observations. The observed excess cannot be accounted for by any plausible change of dust properties. Taking a general form for the virial theorem, we show that a magnetic field strength of ~15{mu}G in SMC clouds could provide additional support for the clouds and explain the difference observed. We conclude that masses of SMC molecular clouds have so far been underestimated. Magnetic pressure may contribute significantly to their support.
- ID:
- ivo://CDS.VizieR/J/A+A/586/A149
- Title:
- SiO in ATLASGAL-selected massive clumps
- Short Name:
- J/A+A/586/A149
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The processes leading to the birth of high-mass stars are poorly understood. The key first step to reveal their formation processes is characterising the clumps and cores from which they form. We define a representative sample of massive clumps in different evolutionary stages selected from the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL), from which we aim to establish a census of molecular tracers of their evolution. As a first step, we study the shock tracer, SiO, mainly associated with shocks from jets probing accretion processes. In low-mass young stellar objects (YSOs), outflow and jet activity decreases with time during the star formation processes. Recently, a similar scenario was suggested for massive clumps based on SiO observations. Here we analyse observations of the SiO (2-1) and (5-4) lines in a statistically significant sample to constrain the change of SiO abundance and the excitation conditions as a function of evolutionary stage of massive star-forming clumps. We performed an unbiased spectral line survey covering the 3-mm atmospheric window between 84-117GHz with the IRAM 30m telescope of a sample of 430 sources of the ATLASGAL survey, covering various evolutionary stages of massive clumps. A smaller sample of 128 clumps has been observed in the SiO (5-4) transition with the APEX telescope to complement the (2-1) line and probe the excitation conditions of the emitting gas. We derived detection rates to assess the star formation activity of the sample, and we estimated the column density and abundance using both an LTE approximation and non-LTE calculations for a smaller subsample, where both transitions have been observed.
- ID:
- ivo://CDS.VizieR/J/ApJS/165/360
- Title:
- SiO maser emission toward 10 late-type stars
- Short Name:
- J/ApJS/165/360
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of simultaneous time monitoring observations of SiO J=2-1 and J=3-2 maser emission for 10 late-type stars (8 Mira variables, 1 OH/IR star, and 1 supergiant) with the 14m radio telescope at Taeduk Radio Astronomy Observatory from 1999 January to 2001 February. The SiO v=1, J=2-1 and J=3-2 maser emission was detected at almost all observational epochs. The SiO v=2, J=2-1 maser was detected from 4 late-type stars (VY CMa, R Cas, Cyg, R Leo) and the v=2, J=3-2 maser was detected from 7 stars (R Aqr, TX Cam, R Cas, Cyg, W Hya, R Leo, IK Tau). The v=3, J=2-1 and masers were also detected from Cyg and TX Cam, respectively. Based on these observational data, line profile and peak velocity variations with respect to stellar velocity, antenna temperatures, and their ratio variations as a function of optical phase of central star were investigated. Description:
- ID:
- ivo://CDS.VizieR/J/ApJ/821/125
- Title:
- SMA obs. of giant molecular clouds in NGC 300
- Short Name:
- J/ApJ/821/125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first high angular resolution study of giant molecular clouds (GMCs) in the nearby spiral galaxy NGC 300, based on observations from the Submillimeter Array (SMA). We target eleven 500pc sized regions of active star formation within the galaxy in the ^12^CO(J=2-1) line at 40pc spatial and 1km/s spectral resolution and identify 45 individual GMCs. We characterize the physical properties of these GMCs, and find that they are similar to GMCs in the disks of the Milky Way and other nearby spiral galaxies. For example, the GMC mass spectrum in our sample has a slope of 1.80+/-0.07. Twelve clouds are spatially resolved by our observations, of which ten have virial mass estimates that agree to within a factor of two with mass estimates derived directly from ^12^CO integrated intensity, suggesting that the majority of these GMCs are bound. The resolved clouds show consistency with Larson's fundamental relations between size, linewidth, and mass observed in the Milky Way. We find that the linewidth scales with the size as {Delta}V{propto}R^0.52+/-0.20^, and the median surface density in the subsample is 54M_{sun}_/pc^2^. We detect ^13^CO in four GMCs and find a mean ^12^CO/^13^CO flux ratio of 6.2. Our interferometric observations recover between 30% and 100% of the integrated intensity from the APEX single dish ^12^CO observations of Faesi et al. (2014, J/ApJ/789/81), suggesting the presence of low-mass GMCs and/or diffuse gas below our sensitivity limit. The fraction of APEX emission recovered increases with the SMA total intensity, as well as with the star formation rate.
- ID:
- ivo://CDS.VizieR/J/A+A/541/L1
- Title:
- SN 1987A images at 350 and 870um
- Short Name:
- J/A+A/541/L1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Supernova 1987A (SN 1987A) in the neighbouring Large Magellanic Cloud offers a superb opportunity to follow the evolution of a supernova and its remnant in unprecedented detail. Recently, far-infrared (far-IR) and sub-mm emission was detected from the direction of SN 1987A, which was interpreted as due to the emission from dust, possibly freshly synthesized in the SN ejecta. To better constrain the location and hence origin of the far-IR and sub-mm emission in SN 1987A, we have attempted to resolve the object in that part of the electro-magnetic spectrum.
- ID:
- ivo://CDS.VizieR/J/A+A/580/A51
- Title:
- SNR G18.8+0.3 data cubes
- Short Name:
- J/A+A/580/A51
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In a previous paper we investigated the molecular environment toward the eastern border of the supernova remnant (SNR) G18.8+0.3. Continuing with the study of the surroundings of this SNR, we now focus on its southern border, which in the radio continuum emission shows a very peculiar morphology with a corrugated corner and a very flattened southern flank. We observed two regions toward the south of SNR G18.8+0.3 using the Atacama Submillimeter Telescope Experiment (ASTE) in the ^12^CO J=3-2. One of these regions was also surveyed in ^13^ CO and C^18^O J=3-2. The angular and spectral resolution of these observations were 22" and 0.11km/s. We compared the CO emission to 20cm radio continuum maps obtained as part of the Multi-Array Galactic Plane Imaging Survey (MAGPIS) and 870um dust emission extracted from the APEX Telescope Large Area Survey of the Galaxy.
- ID:
- ivo://CDS.VizieR/J/ApJ/659/84
- Title:
- Spectroscopy and photometry of z~=5 galaxies
- Short Name:
- J/ApJ/659/84
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new measurement of the integrated stellar mass per comoving volume at redshift 5 determined via spectral energy fitting drawn from a sample of 214 photometrically selected galaxies with z'_850LP_<26.5 in the southern GOODS field. Following recent procedures introduced by Eyles et al. (2007MNRAS.374..910E), we estimate stellar masses for various subsamples for which reliable and unconfused Spitzer IRAC detections are available. A spectroscopic sample of 14 of the most luminous sources with z{bar}=4.92 provides a firm lower limit to the stellar mass density of 1x10^6^M_{sun}_/Mpc^3^. We then consider a larger sample whose photometric redshifts in the publicly available GOODS-MUSIC catalog lie in the range 4.4<z<5.6.
- ID:
- ivo://CDS.VizieR/J/A+A/623/A162
- Title:
- Spectroscopy of CH2(CN)2 and CNCH2CN
- Short Name:
- J/A+A/623/A162
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Nitriles constitute almost 20% of the molecules observed in the interstellar medium, whereas only one dinitrile and one isocyanonitrile compound have been detected up to now. The lack of detections of such compounds may be partially explained by the lack of accurate spectroscopic data on their rotational spectra. Two small seven-atom dinitriles, malononitrile NCCH_2_CN and isocyanoacetonitrile NCCH_2_NC, were chosen as target species for this study. For malononitrile the goal of the study is to systematize all the previous measurements, and to extend the measurements to the sub-millimeter wavelength range. The spectrum of isocyanoacetonitrile has not been studied before. The rotational spectra of the two molecules was measured in the frequency range 150-660GHz using the Lille fast-scan spectrometer. The spectroscopic study was supported by high-level theoretical calculations on the structure of these molecules and their harmonic force field. Accurate frequency predictions for malononitrile and isocyanoacetonitrile were calculated on the basis of the analysis of their rotational spectra. The influence of the spin statistics on the intensities of the lines of malononitrile was taken into account. The provided line lists and sets of molecular parameters meet the needs of astrophysical searches for the two molecules.
- ID:
- ivo://CDS.VizieR/J/ApJ/761/140
- Title:
- Spectroscopy of Herschel-SPIRE galaxies
- Short Name:
- J/ApJ/761/140
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Keck spectroscopic observations and redshifts for a sample of 767 Herschel-SPIRE selected galaxies (HSGs) at 250, 350, and 500{mu}m, taken with the Keck I Low Resolution Imaging Spectrometer and the Keck II DEep Imaging Multi-Object Spectrograph. The redshift distribution of these SPIRE sources from the Herschel Multitiered Extragalactic Survey (HerMES) peaks at z=0.85, with 731 sources at z<2 and a tail of sources out to z~5. We measure more significant disagreement between photometric and spectroscopic redshifts (<{Delta}z/(1+z_spec_)>=0.29) than is seen in non-infrared selected samples, likely due to enhanced star formation rates and dust obscuration in infrared-selected galaxies. The infrared data are used to directly measure integrated infrared luminosities and dust temperatures independent of radio or 24{mu}m flux densities. By probing the dust spectral energy distribution (SED) at its peak, we estimate that the vast majority (72%-83%) of z<2 Herschel-selected galaxies would drop out of traditional submillimeter surveys at 0.85-1mm. This work significantly increased the number of spectroscopically confirmed infrared-luminous galaxies at z{Gt}0 and demonstrates the growing importance of dusty starbursts for galaxy evolution studies and the build-up of stellar mass throughout cosmic time.
