- ID:
- ivo://CDS.VizieR/J/A+A/544/A69
- Title:
- CN(1-0) Zeeman observations of NGC 2264-C
- Short Name:
- J/A+A/544/A69
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- From an observational point of view, the role of magnetic fields in star formation remains unclear, and two main theoretical scenarios have been proposed so far to regulate the star-formation processes. The first model assumes that turbulence in star-forming clumps plays a crucial role, and especially that protostellar outflow-driven turbulence is crucial to support cluster-forming clumps; while the second scenario is based on the consideration of a magnetically-supported clump. Previous studies of the NGC 2264-C protocluster indicate that, in addition to thermal pressure, some extra support might effectively act against the gravitational collapse of this cluster- forming clump. We previously showed that this extra support is not due to the numerous protostellar outflows, nor the enhanced turbulence in this protocluster. Here we present the results of the first polarimetric campaign dedicated to quantifying the magnetic support at work in the NGC 2264-C clump. Our Zeeman observations of the CN(1-0) hyperfine lines provide an upper limit to the magnetic field strength Blos<0.6 mG in the protocluster (projected along the line of sight). While these results do not provide sufficiently tight constraints to fully quantify the magnetic support at work in NGC 2264-C, they suggest that, within the uncertainties, the core could be either magnetically super or sub-critical, with the former being more likely.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/630/A130
- Title:
- Co-added spectra of HD127493 and HZ44
- Short Name:
- J/A+A/630/A130
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Hot subluminous stars can be spectroscopically classified as subdwarf B (sdB) and O (sdO) stars. While the latter are predominantly hydrogen deficient, the former are mostly helium deficient. The atmospheres of most sdOs are almost devoid of hydrogen, whereas a small group of hot subdwarf stars of mixed H/He composition exists, showing extreme metal abundance anomalies. Whether such intermediate helium-rich (iHe) subdwarf stars provide an evolutionary link between the dominant classes is an open question. The presence of strong Ge, Sn, and Pb lines in the UV spectrum of HZ44 suggests a strong enrichment of heavy elements in this iHe-sdO star and calls for a detailed quantitative spectral analysis focusing on trans-iron elements. Non-LTE model atmospheres and synthetic spectra calculated with TLUSTY/SYNSPEC were combined with high-quality optical, ultraviolet (UV), and far-UV (FUV) spectra of HZ44 and its hotter sibling HD127493 to determine their atmospheric parameters and metal abundance patterns. By collecting atomic data from the literature we succeeded in determining the abundances of 29 metals in HZ44, including the trans-iron elements Ga, Ge, As, Se, Zr, Sn, and Pb and providing upper limits for ten other metals. This makes it the best-described hot subdwarf in terms of chemical composition. For HD127493 the abundance of 15 metals, including Ga, Ge, and Pb and upper limits for another 16 metals were derived. Heavy elements turn out to be overabundant by one to four orders of magnitude with respect to the Sun. Zr and Pb are among the most enriched elements. The C, N, and O abundance for both stars can be explained by the nucleosynthesis of hydrogen burning in the CNO cycle along with the stars' helium enrichment. On the other hand, the heavy-element anomalies are unlikely to be caused by nucleosynthesis. Instead diffusion processes are evoked, with radiative levitation overcoming gravitational settlement of the heavy elements.
- ID:
- ivo://CDS.VizieR/J/MNRAS/446/2823
- Title:
- CO and CaT derived sigma in spiral galaxies
- Short Name:
- J/MNRAS/446/2823
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We examine the stellar velocity dispersions ({sigma}) of a sample of 48 galaxies, 35 of which are spirals, from the Palomar nearby galaxy survey. It is known that for ultra-luminous infrared galaxies (ULIRGs) and merger remnants, the {sigma} derived from the near-infrared CO band heads is smaller than that measured from optical lines, while no discrepancy between these measurements is found for early-type galaxies. No such studies are available for spiral galaxies - the subject of this paper. We used cross-dispersed spectroscopic data obtained with the Gemini Near-Infrared Spectrograph, with spectral coverage from 0.85 to 2.5{mu}m, to obtain {sigma} measurements from the 2.29{mu}m CO band heads ({sigma}CO) and the 0.85{mu}m calcium triplet ({sigma}_CaT_). For the spiral galaxies in the sample, we found that {sigma}_CO_ is smaller than {sigma}_CaT_, with a mean fractional difference of 14.3 per cent. The best fit to the data is given by {sigma}_opt_=(46.0+/-18.1)+(0.85+/-0.12){sigma}_CO_. This '{sigma}-discrepancy' may be related to the presence of warm dust, as suggested by a slight correlation between the discrepancy and the infrared luminosity. This is consistent with studies that have found no {sigma}-discrepancy in dust-poor early-type galaxies, and a much larger discrepancy in dusty merger remnants and ULIRGs. That {sigma}_CO_ is lower than {sigma}opt may also indicate the presence of a dynamically cold stellar population component. This would agree with the spatial correspondence between low-{sigma}_CO_ and young/intermediate-age stellar populations that has been observed in spatially resolved spectroscopy of a handful of galaxies.
- ID:
- ivo://CDS.VizieR/J/A+A/628/A72
- Title:
- C_2_O and C_3_O in low-mass star-forming regions
- Short Name:
- J/A+A/628/A72
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- C_2_O and C_3_O belong to the carbon chain oxides family. Both molecules have been detected in the gas phase towards several star-forming regions, and to explain the observed abundances, ion-molecule gas-phase reactions have been invoked. On the other hand, laboratory experiments have shown that carbon chain oxides are formed after energetic processing of CO-rich solid mixtures. Therefore, it has been proposed that they are formed in the solid phase in dense molecular clouds after cosmic ion irradiation of CO-rich icy grain mantles and released in the gas phase after their desorption. In this work, we contribute to the understanding of the role of both gas-phase reactions and energetic processing in the formation of simple carbon chain oxides that have been searched for in various low-mass star-forming regions. We present observations obtained with the Noto-32m and IRAM-30m telescopes towards star-forming regions. We compare these with the results of a gas-phase model that simulates C_2_O and C_3_O formation and destruction, and laboratory experiments in which both molecules are produced after energetic processing (with 200 keV protons) of icy grain mantle analogues. New detections of both molecules towards L1544, L1498, and Elias 18 are reported. The adopted gas phase model is not able to reproduce the observed C_2_O/C_3_O ratios, while laboratory experiments show that the ion bombardment of CO-rich mixtures produces C_2_O/C_3_O ratios that agree with the observed values. Based on the results obtained here, we conclude that the synthesis of both species is due to the energetic processing of CO-rich icy grain mantles. Their subsequent desorption because of non-thermal processes allows the detection in the gas-phase of young star-forming regions. In more evolved objects, the non-detection of both C_2_O and C_3_O is due to their fast destruction in the warm gas.
- ID:
- ivo://CDS.VizieR/J/A+AS/126/3
- Title:
- CO and HI in interacting galaxies
- Short Name:
- J/A+AS/126/3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using SEST, the Parkes antenna and the Australia Telescope Compact Array, we have made a survey of the ^12^CO(1-0) and HI emission of an optically-selected sample of =~60 southern interacting and merging galaxies. In this paper we present the data and determine global masses of neutral gas (in molecular and atomic form) for the observed galaxies. We have detected HI in 26 systems and found that these galaxies have less than 15% of their gas in molecular form.
- ID:
- ivo://CDS.VizieR/J/A+A/554/A55
- Title:
- C^18^O(1-0) and N_2_H^+^(1-0) in L1495/B213
- Short Name:
- J/A+A/554/A55
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Core condensation is a critical step in the star-formation process, but it is still poorly characterized observationally. We have studied the 10pc-long L1495/B213 complex in Taurus to investigate how dense cores have condensed out of the lower density cloud material. We observed L1495/B213 in C^18^O(1-0), N_2_H^+^(1-0), and SO(J_N_=3_2_-2_1_) with the 14m FCRAO telescope, and complemented the data with dust continuum observations using APEX (870um) and IRAM 30m (1200um).
- ID:
- ivo://CDS.VizieR/J/A+A/489/1271
- Title:
- CO and OH abundances of 23 K-M giants
- Short Name:
- J/A+A/489/1271
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Based on the high resolution infrared spectra observed with the Fourier Transform Spectrometer (FTS) at the 4m telescope of the Kitt Peak National Observatory (KPNO), ro-vibrational lines of ^12^C^16^O, ^13^C^16^O, ^12^C^17^O, and ^16^OH were measured. Some details of the observed spectra including the resolution, S/N ratio, and data of observation are given in table2. The spectroscopic and equivalent width data are given in table3 for 23 red giant stars. The resulting data are used to investigate the nature of the infrared spectra of K-M giant stars. It is found that only the weak lines (log(W/nu)<-4.75) carry the information on the photosphere and hence can be used to extract the nature of the photosphere such as the stellar abundances. The intermediate-strength (-4.75<log(W/nu)<-4.40) as well as the strong (log(W/nu)>-4.4) lines are badly disturbed by the lines of non-photospheric origin. In other words, most lines dominating the infrared spectra, except for the weak lines, are actually hybrid of at least two different kinds of lines originating in the photosphere and in an extra molecular layers outside of photosphere. The nature of the extra layers is not known well, but it may be related to the molecular envelope producing H_2_O lines, not only in late M but also in early M giants as well. Also, the intermediate-strength lines include those with LEP as high as 2eV and hence the extra molecular layer should be quite warm. For the reason outlined above, we determine C, O, and their isotopic abundances using only the weak lines, but we listed the measured data not only of the weak lines but also of the stronger lines as well in table3, with the hope that these data can be of some use to clarify the nature of the warm extra molecular layers.
- ID:
- ivo://CDS.VizieR/J/MNRAS/454/3816
- Title:
- Cobalt emission in nebular phase spectra
- Short Name:
- J/MNRAS/454/3816
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The light curves of Type Ia supernovae (SNe Ia) are powered by the radioactive decay of ^56^Ni to ^56^Co at early times, and the decay of ^56^Co to ^56^Fe from ~60 d after explosion. We examine the evolution of the [CoIII] {lambda}5893 emission complex during the nebular phase for SNe Ia with multiple nebular spectra and show that the line flux follows the square of the mass of ^56^Co as a function of time. This result indicates both efficient local energy deposition from positrons produced in ^56^Co decay and long-term stability of the ionization state of the nebula. We compile SN Ia nebular spectra from the literature and present 21 new late-phase spectra of 7 SNe Ia, including SN 2014J. From these we measure the flux in the [CoIII] {lambda}5893 line and remove its well-behaved time dependence to infer the initial mass of ^56^Ni (M_Ni_) produced in the explosion. We then examine ^56^Ni yields for different SN Ia ejected masses (M_ej_ - calculated using the relation between light-curve width and ejected mass) and find that the ^56^Ni masses of SNe Ia fall into two regimes: for narrow light curves (low stretch s~0.7-0.9), M_Ni_ is clustered near M_Ni_~0.4M_{sun}_ and shows a shallow increase as M_ej_ increases from ~1 to 1.4M_{sun}_; at high stretch, M_ej_ clusters at the Chandrasekhar mass (1.4M_{sun}_) while M_Ni_ spans a broad range from 0.6 to 1.2M_{sun}_. This could constitute evidence for two distinct SN Ia explosion mechanisms.
- ID:
- ivo://CDS.VizieR/J/ApJ/829/93
- Title:
- CO, [CI] and [NII] lines from Herschel spectra
- Short Name:
- J/ApJ/829/93
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of all CO (J=4-3 through J=13-12), [CI], and [NII] lines available from extragalactic spectra from the Herschel SPIRE Fourier Transform Spectrometer (FTS) archive combined with observations of the low-J CO lines from the literature and from the Arizona Radio Observatory. This work examines the relationships between L_FIR_, L'_CO_, and L_CO_/L_CO,1-0_. We also present a new method for estimating probability distribution functions from marginal signal-to-noise ratio Herschel FTS spectra, which takes into account the instrumental "ringing" and the resulting highly correlated nature of the spectra. The slopes of log(L_FIR_) versus log(L'_CO_) are linear for all mid- to high-J CO lines and slightly sublinear if restricted to (ultra)luminous infrared galaxies ((U)LIRGs). The mid- to high-J CO luminosity relative to CO J=1-0 increases with increasing L_FIR_, indicating higher excitement of the molecular gas, although these ratios do not exceed ~180. For a given bin in L_FIR_, the luminosities relative to CO J=1-0 remain relatively flat from J=6-5 through J=13-12, across three orders of magnitude of L_FIR_. A single component theoretical photodissociation region (PDR) model cannot match these flat SLED shapes, although combinations of PDR models with mechanical heating added qualitatively match the shapes, indicating the need for further comprehensive modeling of the excitation processes of warm molecular gas in nearby galaxies.
- ID:
- ivo://CDS.VizieR/J/A+A/641/A155
- Title:
- CO+[CI] emission in distant galaxies
- Short Name:
- J/A+A/641/A155
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the detection of multiple carbon monoxide CO line transitions with ALMA in a few tens of infrared-selected galaxies on and above the main sequence at z=1.1-1.7. We reliably detected the emission of CO(5-4), CO(2-1), and CO(7-6)+[CI](2-1) in 50, 33, and 13 galaxies, respectively, and we complemented this information with available CO(4-3) and [CI](1-0) fluxes for part of the sample, and by modeling of the optical-to-millimeter spectral energy distribution. We retrieve a quasi-linear relation between LIR and CO(5-4) or CO(7-6) for main-sequence galaxies and starbursts, corroborating the hypothesis that these transitions can be used as star formation rate (SFR) tracers. We find the CO excitation to steadily increase as a function of the star formation efficiency (SFE), the mean intensity of the radiation field warming the dust (<U>), the surface density of SFR (SigmaSFR), and, less distinctly, with the distance from the main sequence. This adds to the tentative evidence for higher excitation of the CO+[CI] spectral line energy distribution (SLED) of starburst galaxies relative to that for main-sequence objects, where the dust opacities play a minor role in shaping the high-J CO transitions in our sample. However, the distinction between the average SLED of upper main-sequence and starburst galaxies is blurred, driven by a wide variety of intrinsic shapes. Large velocity gradient radiative transfer modeling demonstrates the existence of a highly excited component that elevates the CO SLED of high-redshift main-sequence and starbursting galaxies above the typical values observed in the disk of the Milky Way. This excited component is dense and it encloses ~50% of the total molecular gas mass in main-sequence objects. We interpret the observed trends involving the CO excitation as to be mainly determined by a combination of large SFRs and compact sizes, as a large SigmaSFR is naturally connected with enhanced dense molecular gas fractions and higher dust and gas temperatures, due to increasing ultraviolet radiation fields, cosmic ray rates, as well as dust and gas coupling. We release the full data compilation and the ancillary information to the community.
