- ID:
- ivo://CDS.VizieR/J/MNRAS/452/1523
- Title:
- New young stellar cluster towards IRAS 04186+5143
- Short Name:
- J/MNRAS/452/1523
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of a new young stellar cluster in the outer Galaxy located at the position of an IRAS Point Source Catalog source that has been previously misidentified as an external galaxy. The cluster is seen in our near-infrared imaging towards IRAS 04186+5143 and in archive Spitzer images confirming the young stellar nature of the sources detected. There is also evidence of subclustering seen in the spatial distributions of young stars and of gas and dust. Near- and mid-infrared photometry indicates that the stars exhibit colours compatible with reddening by interstellar and circumstellar dust and are likely to be low- and intermediate-mass young stellar objects (YSOs) with a large proportion of Class I YSOs. Ammonia and CO lines were detected, with the CO emission well centred near the position of the richest part of the cluster. The velocity of the CO and NH3 lines indicates that the gas is Galactic and located at a distance of about 5.5kpc, in the outer Galaxy. Herschel data of this region characterize the dust environment of this molecular cloud core where the young cluster is embedded. We derive masses, luminosities, and temperatures of the molecular clumps where the young stars reside and discuss their evolutionary stages.
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- ID:
- ivo://CDS.VizieR/J/A+A/605/A85
- Title:
- NGC 3293 Chandra X-ray observation
- Short Name:
- J/A+A/605/A85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 3293 is a young stellar cluster at the northwestern periphery of the Carina Nebula Complex that remained poorly explored until now. We want to characterize the stellar population of NGC 3293 in order to evaluate key parameters of the cluster population like the age and the mass function, and to test claims of an abnormal IMF and a deficit of M<=2.5M_{sun}_ stars. WWe performed a deep (70 ksec) X-ray observation of NGC 3293 with Chandra and detected 1026 individual X-ray point sources. These X-ray data directly probe the low-mass (M<=2M_{sun}_) stellar population by means of the strong X-ray emission of young low-mass stars. We identify counterparts for 74% of the X-ray sources in our deep near-infrared images. Our data clearly show that NGC 3293 hosts a large population of ~solar-mass stars, refuting claims of a lack of M<=2.5M_{sun}_ stars. The analysis of the color-magnitude diagram suggests an age of ~8-10Myr for the low-mass population of the cluster. There are at least 511 X-ray detected stars with color-magnitude positions that are consistent with young stellar members within 7 arcmin from the cluster center. The number ratio of X-ray detected stars in the [1-2]M_{sun}_ range versus the M<=5M_{sun}_ stars (known from optical spectroscopy) is well consistent with the expectation from a normal field initial mass function. Most of the early B-type stars and ~20% of the later B-type stars are detected as X-ray sources. Our data shows that NGC 3293 is one of the most populous stellar clusters in the entire Carina Nebula Complex (only excelled by Tr 14, and very similar to Tr 16 and Tr 15). The cluster has probably harbored several O-type stars, the supernova explosions of which may have had an important impact on the early evolution of the Carina Nebula Complex.
- ID:
- ivo://CDS.VizieR/J/ApJ/859/75
- Title:
- NGC 5824 giant star members from VLT obs.
- Short Name:
- J/ApJ/859/75
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 5824 is a massive Galactic globular cluster suspected to have an intrinsic spread in its iron content, according to the strength of the calcium triplet lines. We present chemical abundances of 117 cluster giant stars using high-resolution spectra acquired with the multi-object spectrograph FLAMES. The metallicity distribution of 87 red giant branch stars is peaked at [Fe/H]=-2.11+/-0.01dex, while that derived from 30 asymptotic giant branch stars is peaked at [Fe/H]=-2.20+/-0.01dex. Both the distributions are compatible with a null spread, indicating that this cluster did not retain the ejecta of supernovae. The small iron abundance offset between the two groups of stars is similar to the abundances already observed among red and asymptotic giant branch stars in other clusters. The lack of intrinsic iron spread rules out the possibility that NGC 5824 is the remnant of a disrupted dwarf galaxy, as previously suggested. We also find evidence of the chemical anomalies usually observed in globular clusters, namely the Na-O and the Mg-Al anticorrelations. In particular, NGC 5824 exhibits a huge range of [Mg/Fe] abundance, observed in only a few metal-poor and/or massive clusters. We conclude that NGC 5824 is a normal globular cluster, without spread in [Fe/H] but with an unusually large spread in [Mg/Fe], possibly due to an efficient self-enrichment driven by massive asymptotic giant branch stars.
- ID:
- ivo://CDS.VizieR/J/A+A/606/A121
- Title:
- NGC1333 IRAS 4A ALMA and PdBI maps
- Short Name:
- J/A+A/606/A121
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Hot corinos are extremely rich in complex organic molecules (COMs). Accurate abundance measurements of COMs in such objects are crucial to constrain astrochemical models. In the particular case of close binary systems this can only be achieved through high angular resolution imaging. We aim to perform an interferometric study of multiple COMs in NGC1333 IRAS 4A, which is a protostellar binary hosting hot corino activity, at an angular resolution that is sufficient to distinguish easily the emission from the two cores separated by 1.8". We used the Atacama Large (sub-)Millimeter Array (ALMA) in its 1.2mm band and the IRAM Plateau de Bure Interferometer (PdBI) at 2.7mm to image, with an angular resolution of 0.5" (120au) and 1" (235au), respectively, the emission from 11 different organic molecules in IRAS 4A. This allowed us to clearly disentangle A1 and A2, the two protostellar cores. For the first time, we were able to derive the column densities and fractional abundances simultaneously for the two objects, allowing us to analyse the chemical differences between them. Molecular emission from organic molecules is concentrated exclusively in A2, while A1 appears completely devoid of COMs or even simpler organic molecules, such as HNCO, even though A1 is the strongest continuum emitter. The protostellar core A2 displays typical hot corino abundances and its deconvolved size is 70au. In contrast, the upper limits we placed on COM abundances for A1 are extremely low, lying about one order of magnitude below prestellar values. The difference in the amount of COMs present in A1 and A2 ranges between one and two orders of magnitude. Our results suggest that the optical depth of dust emission at these wavelengths is unlikely to be sufficiently high to completely hide a hot corino in A1 similar in size to that in A2. Thus, the significant contrast in molecular richness found between the two sources is most probably real. We estimate that the size of a hypothetical hot corino in A1 should be less than 12 au. Our results favour a scenario in which the protostar in A2 is either more massive and/or subject to a higher accretion rate than A1, as a result of inhomogeneous fragmentation of the parental molecular clump. This naturally explains the smaller current envelope mass in A2 with respect to A1 along with its molecular richness. The extremely low abundances of organic molecules in A1 with respect to those in A2 demonstrate that the dense inner regions of a young protostellar core lacking hot corino activity may be poorer in COMs than the outer protostellar envelope.
- ID:
- ivo://CDS.VizieR/J/A+A/563/L1
- Title:
- NGC1333-IRAS2A CALYPSO IRAM-PdBI 1mm and 3mm maps
- Short Name:
- J/A+A/563/L1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The structure and kinematics of Class 0 protostars on scales of a few hundred AU is poorly known. Recent observations have revealed the presence of Keplerian disks with a diameter of 150-180AU in L1527-IRS and VLA1623A, but it is not clear if such disks are common in Class 0 protostars. Here we present high-angular-resolution observations of two methanol lines in NGC1333-IRAS2A. We argue that these lines probe the inner envelope, and we use them to study the kinematics of this region. Our observations suggest the presence of a marginal velocity gradient normal to the direction of the outflow. However, the position velocity diagrams along the gradient direction appear inconsistent with a Keplerian disk. Instead, we suggest that the emission originates from the infalling and perhaps slowly rotating envelope, around a central protostar of 0.1-0.2M_{sun}_. If a disk is present, it is smaller than the disks of L1527-IRS and VLA1623A, perhaps suggesting that NGC1333-IRAS2A is younger.
- ID:
- ivo://CDS.VizieR/J/A+A/563/L2
- Title:
- NGC1333-IRAS2A CALYPSO IRAM-PdBI 1mm maps
- Short Name:
- J/A+A/563/L2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the origin of complex organic molecules (COMs) in the gas phase around the low-mass Class 0 protostar NGC 1333-IRAS2A, to determine if the COM emission lines trace an embedded disk, shocks from the protostellar jet, or the warm inner parts of the protostellar envelope. In the framework of the CALYPSO IRAM Plateau de Bure survey, we obtained large bandwidth spectra at sub-arcsecond resolution towards NGC 1333-IRAS2A. We identify the emission lines towards the central protostar and perform Gaussian fits to constrain the size of the emitting region for each of these lines, tracing various physical conditions and scales.
- ID:
- ivo://CDS.VizieR/J/A+A/563/L3
- Title:
- NGC1333-IRAS2A CALYPSO IRAM-PdBI SiO and SO maps
- Short Name:
- J/A+A/563/L3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The earliest evolutionary stages of low-mass protostars are characterised by hot and fast jets which remove angular momentum from the circumstellar disk, thus allowing mass accretion onto the central object. However, the launch mechanism is still being debated. We would like to exploit high-angular (~0.8") resolution and high-sensitivity images to investigate the origin of protostellar jets using typical molecular tracers of shocked regions, such as SiO and SO.
- 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/MNRAS/443/3218
- Title:
- NGC 7538 IRS 1-3 and IRS 9 sources
- Short Name:
- J/MNRAS/443/3218
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present deep and high-resolution (FWHM~0.4-arcsec) near-infrared (NIR) imaging observations of the NGC 7538 IRS 1-3 region (in JHK bands), and IRS 9 region (in HK bands) using the 8.2m Subaru telescope. The NIR analysis is complemented with Giant Metrewave Radio Telescope (GMRT) low-frequency observations at 325, 610, and 1280MHz, molecular line observations of H^13^CO^+^ (J=1-0), and archival Chandra X-ray observations. Using the 'J-H/H-K' diagram, 144 Class II and 24 Class I young stellar object (YSO) candidates are identified in the IRS 1-3 region. Further analysis using 'K/H-K' diagram yields 145 and 96 red sources in the IRS 1-3 and IRS 9 regions, respectively. A total of 27 sources are found to have X-ray counterparts. The YSO mass function (MF), constructed using a theoretical mass-luminosity relation, shows peaks at substellar (~0.08-0.18M_{sun}_) and intermediate (~1-1.78M_{sun}_) mass ranges for the IRS 1-3 region. The MF can be fitted by a power law in the low-mass regime with a slope of {Gamma} ~0.54-0.75, which is much shallower than the Salpeter value of 1.35. An upper limit of 10.2 is obtained for the star to brown dwarf ratio in the IRS 1-3 region. GMRT maps show a compact HII region associated with the IRS 1-3 sources, whose spectral index of 0.87+/-0.11 suggests optical thickness. This compact region is resolved into three separate peaks in higher resolution 1280MHz map, and the 'east' subpeak coincides with the IRS 2 source. H^13^CO^+^ (J=1-0) emission reveals peaks in both IRS 1-3 and IRS 9 regions, none of which are coincident with visible nebular emission, suggesting the presence of dense cloud nearby. The virial masses are approximately of the order of 1000 and 500M_{sun}_ for the clumps in IRS 1-3 and IRS 9 regions, respectively.
- ID:
- ivo://CDS.VizieR/J/A+A/558/A81
- Title:
- NGC 7538 IRS1 maps in CH3OH, HCN and HCO+
- Short Name:
- J/A+A/558/A81
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Revealing the fragmentation, infall, and outflow processes in the immediate environment around massive young stellar objects is crucial for understanding the formation of the most massive stars. With this goal in mind we present the so far highest spatial-resolution thermal submm line and continuum observations toward the young high-mass protostar NGC 7538 IRS1. Using the Plateau de Bure Interferometer in its most extended configuration at 843um wavelength, we achieved a spatial resolution of 0.2"x0.17", corresponding to ~500AU at a distance of 2.7kpc.
