- ID:
- ivo://CDS.VizieR/J/ApJ/897/83
- Title:
- Component structure in the neightborhood of IC 443
- Short Name:
- J/ApJ/897/83
- Date:
- 11 Mar 2022
- Publisher:
- CDS
- Description:
- We present the results of a detailed investigation into the physical conditions in interstellar material interacting with the supernova remnant (SNR) IC443. Our analysis is based on a comprehensive examination of high-resolution far-ultraviolet spectra obtained with the Space Telescope Imaging Spectrograph onboard the Hubble Space Telescope of two stars behind IC443. One of our targets (HD43582) probes gas along the entire line of sight through the SNR, while the other (HD254755) samples material located ahead of the primary supernova shock front. We identify low-velocity quiescent gas in both directions and find that the densities and temperatures in these components are typical of diffuse atomic and molecular clouds. Numerous high- velocity components are observed in the absorption profiles of neutral and singly ionized atomic species toward HD43582. These components exhibit a combination of greatly enhanced thermal pressures and significantly reduced dust-grain depletions. We interpret this material as cooling gas in a recombination zone far downstream from shocks driven into neutral gas clumps. The pressures derived for a group of ionized gas components at high positive velocity toward HD43582 are lower than those of the other shocked components, pointing to pressure inhomogeneities across the remnant. A strong, very high velocity component near -620km/s is seen in the absorption profiles of highly ionized species toward HD43582. The velocity of this material is consistent with the range of shock velocities implied by observations of soft thermal X-ray emission from IC443. Moderately high velocity gas toward HD254755 may represent shocked material from a separate foreground SNR.
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- ID:
- ivo://CDS.VizieR/J/ApJS/178/56
- Title:
- CO observations of LMC Giant Molecular clouds
- Short Name:
- J/ApJS/178/56
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The second survey of the molecular clouds in the Large Magellanic Cloud in ^12^CO(J=1-0) was carried out by NANTEN. The sensitivity of this survey is twice as high as that of the previous NANTEN survey, leading to a detection of molecular clouds with M_CO_>~2x10^4^solMass. We identified 272 molecular clouds, 230 of which are detected at three or more observed positions. We derived the physical properties, such as size, line width, and virial mass, of the 164 GMCs (Giant Molecular clouds) that have an extent more than the beam size of NANTEN in both the major and minor axes.
- ID:
- ivo://CDS.VizieR/J/ApJS/197/16
- Title:
- CO observations of LMC molecular clouds (MAGMA).
- Short Name:
- J/ApJS/197/16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the properties of an extensive sample of molecular clouds in the Large Magellanic Cloud (LMC) mapped at 11pc resolution in the CO(1-0) line. Targets were chosen based on a limiting CO flux and peak brightness as measured by the NANTEN survey. The observations were conducted with the ATNF Mopra Telescope as part of the Magellanic Mopra Assessment. We identify clouds as regions of connected CO emission and find that the distributions of cloud sizes, fluxes, and masses are sensitive to the choice of decomposition parameters.
- ID:
- ivo://CDS.VizieR/J/A+A/627/A107
- Title:
- CO observations of major merger pairs at z=0
- Short Name:
- J/A+A/627/A107
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present CO observations of 78 spiral galaxies in local merger pairs. These galaxies represent a subsample of a Ks-band-selected sample consisting of 88 close major-merger pairs (HKPAIRs), 44 spiral-spiral (S+S) pairs, and 44 spiral-elliptical (S+E) pairs, with separation <20h^-1^kpc and mass ratio <2.5. For all objects, the star formation rate (SFR) and dust mass were derived from Herschel PACS and SPIRE data, and the atomic gas mass, MHI, from the Green Bank Telescope HI observations. The complete data set allows us to study the relation between gas (atomic and molecular) mass, dust mass, and SFR in merger galaxies. We derive the molecular gas fraction (M_H2_/M*), molecular-to-atomic gas mass ratio (M_H2_/M_HI_), gas-to-dust mass ratio and SFE (=SFR/M_H2_) and study their dependences on pair type (S+S compared to S+E), stellar mass, and the presence of morphological interaction signs. We find an overall moderate enhancement (~2x) in both molecular gas fraction (M_H2_/M*) and molecular-to-atomic gas ratio (M_H2_/M_HI_) for star-forming galaxies in major-merger pairs compared to non-interacting comparison samples, whereas no enhancement was found for the SFE nor for the total gas mass fraction ((MHI+MH2)/M^Cstar). When divided into S+S and S+E, low mass and high mass, and with and without interaction signs, there is a small difference in SFE, a moderate difference in M_H2_/M*, and a strong difference in M_H2_/M_HI_ between subsamples. For the molecular-to-atomic gas ratio M_H2_/M_HI_, the difference between S+S and S+E subsamples is 0.55+/-0.18dex and between pairs with and without interaction signs is 0.65+/-0.16dex. Together, our results suggest that (1) star formation enhancement in close major-merger pairs occurs mainly in S+S pairs after the first close encounter (indicated by interaction signs)^Mbecause the HI gas is compressed into star-forming molecular gas by the tidal torque; and (2) this effect is much weakened in the S+E pairs.
- ID:
- ivo://CDS.VizieR/J/ApJS/178/302
- Title:
- C^18^O observations of multiple-core systems
- Short Name:
- J/ApJS/178/302
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of C^18^O observations by the Nobeyama Millimeter Array toward dense clumps with radii of ~0.3pc in six cluster-forming regions including massive (proto) stars. We identified 171 cores, whose radius, line width, and molecular mass range from 0.01 to 0.09pc, 0.43 to 3.33km/s, and 0.5 to 54.1M_{sun}_, respectively. Many cores with various line widths exist in one clump, and the index of the line width-radius relationship of the cores and the parental clump differs from core to core in the clump. This indicates that the degree of dissipation of the turbulent motion varies for each core in one clump.
- ID:
- ivo://CDS.VizieR/J/A+A/644/A64
- Title:
- CO observations of the IC443 SNR
- Short Name:
- J/A+A/644/A64
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Supernova remnants (SNRs) represent a major feedback source from stars in the interstellar medium of galaxies. During the latest stage of supernova explosions, shock waves produced by the initial blast modify the chemistry of gas and dust, inject kinetic energy into the surroundings, and may alter star formation characteristics. Simultaneously, gamma-ray emission is generated by the interaction between the ambient medium and cosmic rays (CRs), including those accelerated in the early stages of the explosion. We study the stellar and interstellar contents of IC443, an evolved shell-type SNR at a distance of 1.9kpc with an estimated age of 30kyr. We aim to measure the mass of the gas and characterize the nature of infrared point sources within the extended G region, which corresponds to the peak of gamma-ray emission detected by VERITAS and Fermi. We performed 10'x10' mapped observations of ^12^CO, ^13^CO J=1-0, J=2-1, and J=3-2 pure rotational lines, as well as C^18^O J=1-0 and J=2-1 obtained with the IRAM 30m and APEX telescopes over the extent of the gamma-ray peak to reveal the molecular structure of the region. We first compared our data with local thermodynamic equilibrium models. We estimated the optical depth of each line from the emission of the isotopologs ^13^CO and C^18^O. We used the population diagram and large velocity gradient assumption to measure the column density, mass, and kinetic temperature of the gas using ^12^CO and ^13^CO lines. We used complementary data (stars, gas, and dust at multiple wavelengths) and infrared point source catalogs to search for protostar candidates. Our observations reveal four molecular structures: a shocked molecular clump associated with emission lines extending between -31 and 16km/s, a quiescent, dark cloudlet associated with a line width of ~2km/s, a narrow ring-like structure associated with a line width of ~1.5km/s, and a shocked knot. We measured a total mass of ~230, ~90, ~210, and ~4M_{sun}_, respectively, for the cloudlet, ring-like structure, shocked clump, and shocked knot. We measured a mass of ~1100M_{sun}_ throughout the rest of the field of observations where an ambient cloud is detected. We found 144 protostar candidates in the region. Our results emphasize how the mass associated with the ring-like structure and the cloudlet cannot be overlooked when quantifying the interaction of CRs with the dense local medium. Additionally, the presence of numerous possible protostars in the region might represent a fresh source of CRs, which must also be taken into account in the interpretation of gamma-ray observations in this region.
- 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.
- ID:
- ivo://CDS.VizieR/J/ApJS/247/29
- Title:
- CO obs. of Planck Galactic cold clumps
- Short Name:
- J/ApJS/247/29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Sixty-five Planck Galactic cold clumps (PGCCs) from the first quadrant (IQuad) and 39 from the anticenter direction region (ACent) were observed in ^12^CO, ^13^CO, and C^18^O J=1-0 lines using the 13.7m telescope of the Purple Mountain Observatory. All the targets were detected in all three lines, except for 12 IQuad and 8 ACent PGCCs without C^18^O detection. Seventy-six and 49 velocity components were obtained in IQuad and ACent respectively; 146 cores were extracted from 76 IQuad clumps and 100 cores from 49 ACent clumps. The average Tex of IQuad cores and ACent cores is 12.4K and 12.1K, respectively. The average line widths of ^13^CO of IQuad cores and ACent cores are 1.55km/s and 1.77km/s, respectively. Among the detected cores, 24 in IQuad and 13 in ACent have asymmetric line profiles. The small blue excesses, ~0.03 in IQuad and 0.01 in ACent, indicate that star formation is not active in these PGCC cores. Power-law fittings of the core mass function to the high-mass end give indices of -0.57 in IQuad and -1.02 in ACent, which are flatter than the slope of the initial mass function given by Salpeter. The large turnover masses of 28M_{sun}_ for IQuad cores and 77M_{sun}_ for ACent cores suggest low star formation efficiencies in PGCCs. The correlation between virial mass and gas mass indicates that most PGCC cores in both regions are not likely pressure-confined.
- ID:
- ivo://CDS.VizieR/J/ApJS/224/7
- Title:
- CO obs. of the outer arm in the 2nd quadrant
- Short Name:
- J/ApJS/224/7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The lack of arm tracers, especially remote tracers, is one of the most difficult problems preventing us from studying the structure of the Milky Way. Fortunately, with its high-sensitivity CO survey, the Milky Way Imaging Scroll Painting (MWISP) project offers such an opportunity. Since completing about one-third of its mission, an area of l=[100,150]{deg}, b=[-3,5]{deg} has nearly been covered. The Outer arm of the Milky Way first clearly revealed its shape in the second galactic quadrant in the form of molecular gas --this is the first time that the Outer arm has been reported in such a large-scale mapping of molecular gas. Using the 115GHz ^12^CO(1-0) data of MWISP at the LSR velocity ~[-100,-60]km/s and in the area mentioned above, we have detected 481 molecular clouds in total, and among them 332 (about 69%) are newly detected and 457 probably belong to the Outer arm. The total mass of the detected Outer arm clouds is ~3.1x10^6^M_{sun}__. Assuming that the spiral arm is a logarithmic spiral, the pitch angle is fitted as ~13.1{deg}. Besides combining both the CO data from MWISP and the 21cm HI data from the Canadian Galactic Plane Survey (CGPS), the gas distribution, warp, and thickness of the Outer arm are also studied.
- ID:
- ivo://CDS.VizieR/J/ApJS/242/19
- Title:
- CO outflow candidates toward W3/4/5 complex
- Short Name:
- J/ApJS/242/19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the Purple Mountain Observatory Delingha 13.7m telescope, we conducted a large-scale ^12^CO(J=1->0) outflow survey (over ~110deg^2^) toward the W3/4/5 complex and its surroundings. In total, 459 outflow candidates were identified. Approximately 62% (284) were located in the Perseus arm, including the W3/4/5 complex and its surroundings, while ~35% (162) were located in the Local arm, ~1% (5) were in the Outer arm, and ~2% (8) were in two interarm regions. This result indicated that star formation was concentrated in the Galactic spiral arms. The detailed spatial distribution of the outflow candidates showed that the Perseus arm presented the most active star formation among the study regions. The W3/4/5 complex is a great region to research massive star formation in a triggered environment. A key region, which has been well studied by other researches, is in the eastern high-density W3 complex that neighbors the W4 complex. Two shell-like structures in the Local arm contain candidates that can be used to study the impact on star formation imposed by massive or intermediate-mass stars in relatively isolated systems. The majority of outflow candidates in the two interarm regions and the Outer arm are located in filamentary structures.
