- ID:
- ivo://CDS.VizieR/J/ApJS/206/22
- Title:
- Newly EGOs from GLIMPSE II survey. II. MoC
- Short Name:
- J/ApJS/206/22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have undertaken a survey of molecular lines in the 3mm band toward 57 young stellar objects using the Australia Telescope National Facility Mopra 22m radio telescope. The target sources were young stellar objects with active outflows (extended green objects (EGOs)) newly identified from the GLIMPSE II survey. We observe a high detection rate (50%) of broad line wing emission in the HNC and CS thermal lines, which combined with the high detection rate of class I methanol masers toward these sources (reported in Paper I, Cat. J/ApJS/206/9) further demonstrates that the GLIMPSE II EGOs are associated with outflows. The physical and kinematic characteristics derived from the 3mm molecular lines for these newly identified EGOs are consistent with these sources being massive young stellar objects with ongoing outflow activity and rapid accretion. These findings support our previous investigations of the mid-infrared properties of these sources and their association with other star formation tracers (e.g., infrared dark clouds, methanol masers and millimeter dust sources) presented in Paper I. The high detection rate (64%) of the hot core tracer CH_3_CN reveals that the majority of these new EGOs have evolved to the hot molecular core stage. Comparison of the observed molecular column densities with predictions from hot core chemistry models reveals that the newly identified EGOs from the GLIMPSE II survey are members of the youngest hot core population, with an evolutionary time scale of the order of 10^3^yr.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJS/196/4
- Title:
- New young star candidates in Taurus-Auriga
- Short Name:
- J/ApJS/196/4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Taurus Molecular Cloud subtends a large solid angle on the sky, in excess of 250deg^2^. The search for legitimate Taurus members to date has been limited by sky coverage as well as the challenge of distinguishing members from field interlopers. The Wide-field Infrared Survey Explorer has recently observed the entire sky, and we take advantage of the opportunity to search for young stellar object (YSO) candidate Taurus members from a ~260deg^2^ region designed to encompass previously identified Taurus members. We use near- and mid-infrared colors to select objects with apparent infrared excesses and incorporate other catalogs of ancillary data to present a list of rediscovered Taurus YSOs with infrared excesses (taken to be due to circumstellar disks), a list of rejected YSO candidates (largely galaxies), and a list of 94 surviving candidate new YSO-like Taurus members. There is likely to be contamination lingering in this candidate list, and follow-up spectra are warranted.
- 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.
- ID:
- ivo://CDS.VizieR/J/MNRAS/454/3597
- Title:
- NGC 2282 BVI Ha observations
- Short Name:
- J/MNRAS/454/3597
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the analysis of the stellar content of NGC 2282, a young cluster in the Monoceros constellation, using deep optical BVI and INT Photometric H{alpha} Survey (IPHAS) photometry along with infrared (IR) data from UKIRT Infrared Deep Sky Survey and Spitzer-IRAC. Based on the stellar surface density analysis using nearest neighbourhood method, the radius of the cluster is estimated as ~3.15-arcmin. From optical spectroscopic analysis of eight bright sources, we have classified three early B-type members in the cluster, which includes, HD 289120, a previously known B2V-type star, a Herbig Ae/Be star (B0.5 Ve) and a B5 V star. From spectrophotometric analyses, the distance to the cluster has been estimated as ~1.65kpc. The K-band extinction map is estimated using nearest neighbourhood technique, and the mean extinction within the cluster area is found to be A_V_~3.9mag. Using IR colour-colour criteria and H{alpha}-emission properties, we have identified a total of 152 candidate young stellar objects (YSOs) in the region, of which, 75 are classified as Class II, nine are Class I YSOs. Our YSO catalogue also includes 50 H{alpha}-emission line sources, identified using slitless spectroscopy and IPHAS photometry data. Based on the optical and near-IR colour-magnitude diagram analyses, the cluster age has been estimated to be in the range of 2-5Myr, which is in agreement with the estimated age from disc fraction (~58 per cent). Masses of these YSOs are found to be ~0.1-2.0M_{sun}_. Spatial distribution of the candidate YSOs shows spherical morphology, more or less similar to the surface density map.
- 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/558/A58
- Title:
- NGC 1333-IRAS 4A C^18^O, NO and O_2_ spectra
- Short Name:
- J/A+A/558/A58
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- According to traditional gas-phase chemical models, O_2_ should be abundant in molecular clouds, but until recently, attempts to detect interstellar O_2_ line emission with ground- and space-based observatories have failed. Following the multi-line detections of O_2_ with low abundances in the Orion and rho Oph A molecular clouds with Herschel, it is important to investigate other environments, and we here quantify the O_2_ abundance near a solar-mass protostar. Observations of molecular oxygen, O_2_, at 487GHz toward a deeply embedded low-mass Class 0 protostar, NGC 1333-IRAS 4A, are presented, using the Heterodyne Instrument for the Far Infrared (HIFI) on the Herschel Space Observatory. Complementary data of the chemically related NO and CO molecules are obtained as well. The high spectral resolution data are analysed using radiative transfer models to infer column densities and abundances, and are tested directly against full gas-grain chemical models. The deep HIFI spectrum fails to show O_2_ at the velocity of the dense protostellar envelope, implying one of the lowest abundance upper limits of O_2_/H_2_ at <6x10^-3^ (3 sigma). The O_2_/CO abundance ratio is less than 0.005. However, a tentative (4.5 sigma) detection of O_2_ is seen at the velocity of the surrounding NGC1333 molecular cloud, shifted by 1km/s relative to the protostar. For the protostellar envelope, pure gas-phase models and gas-grain chemical models require a long pre-collapse phase (~0.7-1x10^6^-years), during which atomic and molecular oxygen are frozen out onto dust grains and fully converted to H_2_O, to avoid overproduction of O_2_ in the dense envelope. The same model also reproduces the limits on the chemically related NO molecule if hydrogenation of NO on the grains to more complex molecules such as NH_2_OH, found in recent laboratory experiments, is included. The tentative detection of O_2_ in the surrounding cloud is consistent with a low-density PDR model with small changes in reaction rates. The low O_2_ abundance in the collapsing envelope around a low-mass protostar suggests that the gas and ice entering protoplanetary disks is very poor in O_2_.
- ID:
- ivo://CDS.VizieR/J/A+A/568/A125
- Title:
- NGC 1333 IRAS 4A H_2_O observations
- Short Name:
- J/A+A/568/A125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Water is a key molecule in protostellar environments because its line emission is very sensitive to both the chemistry and the physical conditions of the gas. Observations of H_2_O line emission from low-mass protostars and their associated outflows performed with HIFI onboard the Herschel Space Observatory have highlighted the complexity of H_2_O line profiles, in which different kinematic components can be distinguished. The goal is to study the spatial distribution of H_2_O, in particular of the different kinematic components detected in H_2_O emission, at two bright shocked regions along IRAS4A, one of the strongest H_2_O emitters among the Class 0 outflows. We obtained Herschel-PACS maps of the IRAS4A outflow and HIFI observations of two shocked positions. The largest HIFI beam of 38" at 557GHz was mapped in several key water lines with different upper energy levels, to reveal possible spatial variations of the line profiles. A large velocity gradient (LVG) analysis was performed to determine the excitation conditions of the gas.
- 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_.
