- ID:
- ivo://CDS.VizieR/J/A+A/599/A9
- Title:
- NGC 4214 [CII] line profile
- Short Name:
- J/A+A/599/A9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We used SOFIA/GREAT [CII] 158um observations as well as HI data from THINGS and CO(2-1) data from HERACLES to decompose the spectrally resolved [CII] line profiles in NGC4124 into components associated with neutral atomic and molecular gas. We infer gas masses traced by [CII] under different ISM conditions. We find that the molecular gas mass is dominated by CO-dark gas and that we can only assign 9 percent of [CII] intensity to the cold neutral medium.
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- ID:
- ivo://CDS.VizieR/J/A+A/632/A83
- Title:
- NGC 6334 filament with ALMA
- Short Name:
- J/A+A/632/A83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Herschel imaging surveys of galactic interstellar clouds support a paradigm for low-mass star formation in which dense molecular filaments play a crucial role. The detailed fragmentation properties of star-forming filaments remain poorly understood, however, and the validity of the filament paradigm in the intermediate- to high-mass regime is still unclear. Here, following up on an earlier 350um dust continuum study with the ArTeMiS camera on the APEX telescope, we investigate the detailed density and velocity structure of the main filament in the high-mass star-forming region NGC 6334. We conducted ALMA Band 3 observations in the 3.1mm continuum and of the N_2_H^+^(1-0), HC_5_N(36-35), HNC(1-0), HC_3_N(10-9), CH_3_CCH(6-5), and H_2_CS(3-2) lines at an angular resolution of 300, corresponding to 0.025 pc at a distance of 1.7kpc. The NGC 6334 filament was detected in both the 3.1mm continuum and the N_2_H^+^, HC_3_N, HC_5_N, CH_3_CCH, and H_2_CS lines with ALMA. We identified twenty-six compact (<0.03pc) dense cores at 3.1mm and five velocity-coherent fiber-like features in N_2_H^+^ within the main filament. The typical length (~0.5pc) of, and velocity difference (~0.8km/s) between, the fiber-like features of the NGC 6334 filament are reminiscent of the properties for the fibers of the low-mass star-forming filament B211/B213 in the Taurus cloud. Only two or three of the five velocity-coherent features are well aligned with the NGC 6334 filament and may represent genuine, fiber sub-structures; the other two features may trace accretion flows onto the main filament. The mass distribution of the ALMA 3.1mm continuum cores has a peak at 10 M, which is an order of magnitude higher than the peak of the prestellar core mass function in nearby, low-mass star-forming clouds. The cores can be divided into seven groups, closely associated with dense clumps seen in the ArTeMiS 350um data. The projected separation between ALMA dense cores (0.03-0.1pc) and the projected spacing between ArTeMiS clumps (0.2-0.3pc) are roughly consistent with the effective Jeans length (0.08+/-0.03pc) in the filament and a physical scale of about four times the filament width, respectively, if the inclination angle of the filament to line of sight is ~30{deg}. These two distinct separation scales are suggestive of a bimodal fragmentation process in the filament. Despite being one order of magnitude denser and more massive than the Taurus B211/B213 filament, the NGC 6334 filament has a density and velocity structure that is qualitatively very similar. The main difference is that the dense cores embedded in the NGC 6334 filament appear to be an order of magnitude denser and more massive than the cores in the Taurus filament. This suggests that dense molecular filaments may evolve and fragment in a similar manner in low- and high-mass star-forming regions, and that the filament paradigm may hold in the intermediate-mass (if not high-mass) star formation regime.
- ID:
- ivo://CDS.VizieR/J/A+A/637/A63
- Title:
- NGC 1333-IRAS4A radio images
- Short Name:
- J/A+A/637/A63
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Low-mass protostars drive powerful molecular outflows that can be observed with millimetre and submillimetre telescopes. Various sulfuretted species are known to be bright in shocks and could be used to infer the physical and chemical conditions throughout the observed outflows. The evolution of sulfur chemistry is studied along the outflows driven by the NGC1333-IRAS4A protobinary system located in the Perseus cloud to constrain the physical and chemical processes at work in shocks. We observed various transitions from OCS, CS, SO, and SO_2_ towards NGC1333-IRAS4A in the 1.3, 2, and 3mm bands using the {IRAM NOrthern Extended Millimeter Array (NOEMA)} and we interpreted the observations through the use of the Paris-Durham shock model. The targeted species clearly show different spatial emission along the two outflows driven by IRAS4A. OCS is brighter on small and large scales along the south outflow driven by IRAS4A1, whereas SO_2_ is detected rather along the outflow driven by IRAS4A2 that is extended along the north east - south west (NE-SW) direction. SO is detected at extremely high radial velocity up to +25km/s relative to the source velocity, clearly allowing us to distinguish the two outflows on small scales. Column density ratio maps estimated from a rotational diagram analysis allowed us to confirm a clear gradient of the OCS/SO_2_ column density ratio between the IRAS4A1 and IRAS4A2 outflows. Analysis assuming non Local Thermodynamic Equilibrium of four SO$_2$ transitions towards several SiO emission peaks suggests that the observed gas should be associated with densities higher than 10^5^cm^-3^ and relatively warm (T>100K) temperatures in most cases. The observed chemical differentiation between the two outflows of the IRAS4A system could be explained by a different chemical history. The outflow driven by IRAS4A1 is likely younger and more enriched in species initially formed in interstellar ices, such as OCS, and recently sputtered into the shock gas. In contrast, the longer and likely older outflow triggered by IRAS4A2 is more enriched in species that have a gas phase origin, such as SO_2_.
- ID:
- ivo://CDS.VizieR/J/A+A/613/A29
- Title:
- NGC1333-IRAS2A water snowline imaging
- Short Name:
- J/A+A/613/A29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Snowlines are key ingredients for planet formation. Providing observational constraints on the locations of the major snowlines is therefore crucial for fully connecting planet compositions to their formation mechanism. Unfortunately, the most important snowline, that of water, is very difficult to observe directly in protoplanetary disks due to its close proximity to the central star. Based on chemical considerations, HCO^+^ is predicted to be a good chemical tracer of the water snowline, because it is particularly abundant in dense clouds when water is frozen out. This work aims to map the optically thin isotopologue H^13^CO^+^ toward the envelope of the low-mass protostar NGC1333-IRAS2A, where the snowline is at larger distance from the star than in disks. Comparison with previous observations of H_2_^18^O will show whether H^13^CO^+^ is indeed a good tracer of the water snowline. NGC1333-IRAS2A was observed using NOEMA at ~0.9 arcsec resolution, targeting the H^13^CO^+^ J=3-2 transition at 260.255GHz. The integrated emission profile was analyzed using 1D radiative transfer modeling of a spherical envelope with a parametrized abundance profile for H^13^CO^+^. This profile was validated with a full chemical model. The H^13^CO^+^ emission peaks ~2-arcsec northeast of the continuum peak, whereas H_2_^18^O shows compact emission on source. Quantitative modeling shows that a decrease in H13CO+ abundance by at least a factor of six is needed in the inner ~360AU to reproduce the observed emission profile. Chemical modeling predicts indeed a steep increase in HCO^+^ just outside the water snowline; the 50% decrease in gaseous H_2_O at the snowline is not enough to allow HCO^+^ to be abundant. This places the water snowline at 225AU, further away from the star than expected based on the 1D envelope temperature structure for NGC1333-IRAS2A. In contrast, DCO^+^ observations show that the CO snowline is at the expected location, making an outburst scenario unlikely. The spatial anticorrelation of the H^13^CO^+^ and H_2_^18^O emission provide a proof of concept that H^13^CO^+^ can be used as a tracer of the water snowline.
- ID:
- ivo://CDS.VizieR/J/A+A/625/A134
- Title:
- NGC 6357 massive dense cores
- Short Name:
- J/A+A/625/A134
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To constrain models of high-mass star formation it is important to identify the massive dense cores (MDCs) able to form high-mass star(s). It is one of purposes of the Herschel/HOBYS key program. Here, we make the census and characterisation of the properties of the MDCs population of the NGC 6357 HII region. Our study is based on the Herschel PACS and SPIRE 70-500 microns images of NGC 6357 complemented with (sub)millimetre and mid-infrared data. We followed the procedure, established by the Herschel/HOBYS consortium, to extract ~0.1pc massive dense cores using the getsources software. We estimated their physical parameters (temperatures, masses, luminosities) from spectral energy distribution (SED) fitting. We have obtained a complete census of 23 massive dense cores, amongs which one is found to be IR-quiet and twelve are starless, representing very early stages of the star-formation process. Focussing on the starless MDCs, we consider their evolutionary status, and suggest that only five are likely to form a high-mass star. We find that, contrarily to the case in NGC 6334, the NGC 6357 region does not exhibit any ridge/hub features that are believed to be crucial to the massive star formation process. This study adds support for an empirical model in which massive dense cores and protostars simultaneously accrete mass from the surrounding filaments. In addition, the massive star formation in NGC 6357 seems to have stopped and the hottest stars in Pismis 24 have disrupted the filaments.
- ID:
- ivo://CDS.VizieR/J/A+A/647/A154
- Title:
- NGC6357 686 molecular cores physical properties
- Short Name:
- J/A+A/647/A154
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We mapped the NGC6357 star forming region at 450 and 850 micron with SCUBA-2 and in the CO(3-2) line with HARP at the JCMT. We also retrieved Herschel Hi-GAL data at 70 and 160 micron. The submm continuum emission was decomposed into cores with the algorithm Gaussclumps (Stutzki & Guesten, 1990ApJ...356..513S). By fitting greybodies to the core 4-point SEDs we derived their temperature and mass. Core mass functions were derived in the region more exposed to the FUV flux from massive stars (associated with the HII regions G353.2+0.9, G353.1+0.6, and G353.2+0.7) and in the region less exposed. Table 2 lists the physical properties of the cores in NGC6357.
- ID:
- ivo://CDS.VizieR/J/A+A/618/A104
- Title:
- NGC3278, SN2009bb host, ATCA and MUSE data
- Short Name:
- J/A+A/618/A104
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The host galaxies of gamma-ray bursts (GRBs) have been claimed to have experienced a recent inflow of gas from the intergalactic medium. This is because their atomic gas distribution is not centred on their optical emission and because they are deficient in molecular gas given their high star-formation rates. Similar studies have not been conducted for host galaxies of relativistic supernovae (SNe), which may have similar progenitors. The potential similarity of the powering mechanisms of relativistic SNe and GRBs allowed us to make a prediction that relativistic SNe are born in environments similar to those of GRBs, i.e. rich in atomic gas. Here we embark on testing this hypothesis by analysing the properties of the host galaxy NGC 3278 of the relativistic SN 2009bb. This is the first time the atomic gas properties of a relativistic SN host is analysed and the first time resolved 21cm hydrogen line (HI) information is provided for a host of a SN of any type. We obtained radio observations with Australia Telescope Compact Array (ATCA) covering HI line; and optical integral field unit spectroscopy observations with Multi Unit Spectroscopic Explorer (MUSE) at the Very Large Telescope (VLT). Moreover, we analysed archival carbon monoxide (CO) and broad-band data for this galaxy. The atomic gas distribution of NGC3278 is not centred on the optical galaxy centre, but instead around a third of atomic gas resides in the region close to the SN position. This galaxy has a few times lower atomic and molecular gas masses than predicted from its star formation rate (SFR). Its specific star formation rate (sSFR=SFR/M*) is ~2-3 times higher than the main-sequence value, placing it at the higher end of the main sequence towards starburst galaxies. SN 2009bb exploded close to the region with the highest SFR density and the lowest age, as evident from high Halpha EW, corresponding to the age of the stellar population of ~5.5Myr. Assuming this timescale was the lifetime of the progenitor star, its initial mass would have been close to ~36M_{sun}_. As for GRB hosts, the gas properties of NGC3278 are consistent with a recent inflow of gas from the intergalactic medium, which explains the concentration of atomic gas close to the SN position and the enhanced SFR. Super-solar metallicity at the position of the SN (unlike for most of GRBs) may mean that relativistic explosions signal a recent inflow of gas (and subsequent star-formation), and their type (GRBs or SNe) is determined by either i) the metallicity of the inflowing gas (metal-poor gas results in a GRB explosion and metal-rich gas in a relativistic SN explosion without an accompanying GRB), or ii) by the efficiency of gas mixing (efficient mixing for SN hosts leading to quick disappearance of metal-poor regions), or iii) by the type of the galaxy (more metal-rich galaxies would result in only a small fraction of star-formation to be fuelled by metal-poor gas).
- ID:
- ivo://CDS.VizieR/J/ApJ/806/74
- Title:
- NH3 line profiles in star-forming regions
- Short Name:
- J/ApJ/806/74
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Anomalous ammonia (NH_3_) spectra, exhibiting asymmetric hyperfine satellite intensity profiles in the (J,K)=(1,1) inversion transition, have been observed in star-forming regions for over 35 years. We present a systematic study of this "hyperfine intensity anomaly" (HIA) toward a sample of 334 high-mass star forming regions: 310 high-mass (>~100M_{sun}_) clumps and 24 infrared dark clouds. The HIA is ubiquitous in high-mass star forming regions. Although LTE excitation predicts that the intensity ratios of the outer satellites and inner satellites are exactly unity, for this sample the ensemble average ratios are 0.812+/-0.004 and 1.125+/-0.005, respectively. We have quantified the HIA and find no significant relationships between the HIA and temperature, line width, optical depth, and the stage of stellar evolution. The fact that HIAs are common in high-mass star-forming regions suggests that the conditions that lead to HIAs are ubiquitous in these regions. A possible link between HIAs and the predictions of the competitive accretion model of high-mass star formation is suggested; however, the expected trends of HIA strength with clump evolutionary stage, rotational temperature, and line width for evolving cores in competitive accretion models are not found. Thus, the exact gas structures that produce HIAs remain unknown. Turbulent gas structures are a possible explanation, but the details need to be explored.
- ID:
- ivo://CDS.VizieR/J/A+A/472/519
- Title:
- N2H+(1-0) maps of Ophiuchus main cloud
- Short Name:
- J/A+A/472/519
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The earliest phases of clustered star formation and the origin of the stellar initial mass function (IMF) are currently much debated. In order to constrain the origin of the IMF, we investigated the internal and relative motions of starless condensations and protostars previously detected by us in the dust continuum at 1.2mm in the L1688 protocluster of the Ophiuchus molecular cloud complex. The starless condensations have a mass spectrum resembling the IMF and are therefore likely representative of the initial stages of star formation in the protocluster. We carried out detailed molecular line observations, including some N2H+(1-0) mapping, of the Ophiuchus protocluster condensations using the IRAM 30m telescope. We measured subsonic or at most transonic levels of internal turbulence within the condensations, implying virial masses which generally agree within a factor of ~2 with the masses derived from the 1.2mm dust continuum. This supports the notion that most of the L1688 starless condensations are gravitationally bound and prestellar in nature. We measured a global one-dimensional velocity dispersion of less than 0.4km/s between condensations. This small relative velocity dispersion implies that, in general, the condensations do not have time to interact with one another before evolving into pre-main-sequence objects. Our observations support the view that the IMF is partly determined by cloud fragmentation at the prestellar stage. Competitive accretion is unlikely to be the dominant mechanism at the protostellar stage in the Ophiuchus protocluster, but it may possibly govern the growth of starless, self-gravitating condensations initially produced by gravoturbulent fragmentation toward an IMF, Salpeter-like mass spectrum.
- ID:
- ivo://CDS.VizieR/J/A+A/587/A118
- Title:
- N2H+, N2D+ and C17O spectra in Ophiuchus
- Short Name:
- J/A+A/587/A118
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In cold (T<25K) and dense (n_H_>10^4^cm^-3^) interstellar clouds, molecules such as CO are significantly frozen onto dust grain surfaces. Deuterium fractionation is known to be very efficient in these conditions as CO limits the abundance of H_3_^+^, which is the starting point of deuterium chemistry. In particular, N_2_D^+^ is an excellent tracer of dense and cold gas in star- forming regions. We measure the deuterium fraction, RD, and the CO depletion factor, fd, towards a number of starless and protostellar cores in the L1688 region of the Ophiuchus molecular cloud and search for variations based upon environmental differences across L1688. The kinematic properties of the dense gas traced by the N_2_H^+^ and N_2_D^+^ (1-0) lines are also discussed. Deuterium fraction has been measured via observations of the J=1-0 transition of N2H+ and N2D+ towards 33 dense cores in different regions of L1688. We estimated the CO depletion factor using C^17^O(1-0) and 850 micron dust continuum emission from the SCUBA survey. We carried out all line observations with the IRAM 30 meter antenna.
