- ID:
- ivo://CDS.VizieR/J/A+A/597/A45
- Title:
- W51 line of sight deuterium fractionation
- Short Name:
- J/A+A/597/A45
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Herschel/HIFI observations toward the compact HII region W51 has revealed the presence of a cold dense core along its line of sight in a high-velocity stream located just in front of W51. This detection has been made possible through absorption measurements of low-energy transitions of HDO, NH_3_, and C_3_ against the bright background emitted by the star-forming region. We present a follow-up study of this core using the high sensitivity and high spectral resolution provided by the IRAM 30m telescope. We report new detections of this core in absorption for DCO^+^ (2-1, 3-2), H^13^CO^+^ (1-0), DNC (3-2), HN^13^C (1-0), p-H_2_CO (2_0,2_-1_0,1_, 3_0,3_-2_0,2_), and in emission for o-NH2D. We also report interferometric observation of this last species using the IRAM/NOEMA telescope, revealing the fragmented nature of the source through the detection of two cores, separated by 0.19-0.24pc, with average sizes of less than 0.16-0.19pc. From a non-LTE analysis, we are able to estimate the density (~2.5x10^4^cm^-3^) and temperature (~10K) of this component, typical of what is found in dark clouds. This component (called W51-core) has the same DCO^+^/HCO^+^ ratio (0.02) as TMC-1 and a high DNC/HNC ratio (0.14). Detection of these deuterated species indicates that W51-core is similar to an early-phase low-mass star-forming region, formed from the interaction between the W51 giant molecular cloud and the high-velocity stream in front of it. The W51 complex being at about 5kpc, these findings lead to what is the first detection of the earliest phase of low-mass star-forming region at such a large distance.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/636/A38
- Title:
- W43-MM1 ALMA ^12^CO(2-1) datacube
- Short Name:
- J/A+A/636/A38
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The accretion history of protostars remains widely mysterious even though it represents one of the best ways to understand the protostellar collapse that leads to the formation of stars. Molecular outflows, which are easier to detect than the direct accretion onto the prostellar embryo, are here used to characterize the protostellar accretion phase in W43-MM1. The W43-MM1 protocluster hosts a sufficient number of protostars to statistically investigate molecular outflows in a single, homogeneous region. We used the CO(2-1) and SiO(5-4) line datacubes, taken as part of an ALMA mosaic with a 2000 AU resolution, to search for protostellar outflows, evaluate the influence that the environment has on these outflows' characteristics and put constraints on outflow variability in W43-MM1. We discovered a rich cluster of 46 outflow lobes, driven by 27 protostars with masses of 1-100M_{sun}_. The complex environment inside which these outflow lobes develop has a definite influence on their length, limiting the validity of using outflow's dynamical timescales as a proxy of the ejection timescale in clouds with high dynamics and varying conditions. We performed a detailed study of Position-Velocity (PV) diagrams of outflows that revealed clear events of episodic ejection. The time variability of W43-MM1 outflows is a general trend and is more generally observed than in nearby, low- to intermediate-mass star-forming regions. The typical timescale found between two ejecta, ~500yr, is consistent with that found in nearby protostars. If ejection episodicity reflects variability in the accretion process, either protostellar accretion is more variable or episodicity is easier to detect in high-mass star-forming regions than in nearby clouds. The timescale found between accretion events could be resulting from instabilities, associated with bursts of inflowing gas arising from the close dynamical environment of highmass star-forming cores.
- ID:
- ivo://CDS.VizieR/J/A+A/417/421
- Title:
- WSRT wide-field HI survey. II.
- Short Name:
- J/A+A/417/421
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used the Westerbork array to carry out an unbiased wide-field survey for HI emission features, achieving an RMS sensitivity of about 18mJy/Beam at a velocity resolution of 17km/s over 1800deg^2^ and between -1000<VHel<+6500km/s. The primary data consists of auto-correlation spectra with an effective angular resolution of 49' FWHM. The survey region is centered approximately on the position of Messier 31 and is Nyquist-sampled over 60x30deg in RAxDE. In this paper we present our HI detections at negative velocities which could be distinguished from the Galactic foreground. Fully 29% of the entire survey area has high velocity HI emission at a column density exceeding our 3-sigma limit of about 1.5x10^17cm^-2 over 30km/s. We tabulate the properties of 95 discrete HVC components in the field, corresponding to more than an order of magnitude increase in number over that known previously. The distribution of discrete object number with flux density has an inflection point near 12Jy.km/s which may correspond to a characteristic mass and distance for this population. A complete description of the observations and general methods of data reduction has already been given in Paper I (Braun et al., Cat. <J/A+A/406/829>).
- ID:
- ivo://CDS.VizieR/J/ApJ/900/L10
- Title:
- X-band data of the GOTHAM Large Project for TMC-1
- Short Name:
- J/ApJ/900/L10
- Date:
- 15 Feb 2022 11:45:23
- Publisher:
- CDS
- Description:
- We present an overview of the GBT Observations of TMC-1: Hunting Aromatic Molecules Large Program on the Green Bank Telescope. This and a related program were launched to explore the depth and breadth of aromatic chemistry in the interstellar medium at the earliest stages of star formation, following our earlier detection of benzonitrile (c-C6H5CN) in TMC-1. In this work, details of the observations, use of archival data, and data reduction strategies are provided. Using these observations, the interstellar detection of propargyl cyanide (HCCCH2CN) is described, as well as the accompanying laboratory spectroscopy. We discuss these results, and the survey project as a whole, in the context of investigating a previously unexplored reservoir of complex, gas-phase molecules in pre-stellar sources. A series of companion papers describe other new astronomical detections and analyses.
- ID:
- ivo://CDS.VizieR/J/A+A/468/379
- Title:
- XMM Optical Monitor Survey of TMC
- Short Name:
- J/A+A/468/379
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Optical Monitor (OM) on-board XMM-Newton obtained optical/ultraviolet data for the XMM-Newton Extended Survey of the Taurus Molecular Cloud (XEST), simultaneously with the X-ray detectors. With the XEST OM data, we study the optical and ultraviolet properties of TMC members, and to perform correlative studies between the X-ray and OM light curves. In particular, we aim to determine whether accretion plays a significant role in the optical/ultraviolet and X-ray emissions. The Neupert effect in stellar flares is also investigated. Coordinates, average count rates and magnitudes were extracted from OM images, together with light curves with low time resolution (a few kiloseconds). For a few sources, OM FAST mode data were also available, and we extracted OM light curves with high time resolution. The OM data were correlated with Two Micron All Sky Survey (2MASS) data and with the XEST catalogue in the X-rays. The XEST OM catalogue contains 2,148 entries of which 1,893 have 2MASS counterparts. However, only 98 entries have X-ray counterparts, of which 51 are known TMC members and 12 additional are TMC candidates. The OM data indicate that accreting stars are statistically brighter in the U band than non-accreting stars after correction for extinction, and have U-band excesses, most likely due to accretion. The OM emission of accreting stars is variable, probably due to accretion spots, but it does not correlate with the X-ray light curve, suggesting that accretion does not contribute significantly to the X-ray emission of most accreting stars. In some cases, flares were detected in both X-ray and OM light curves and followed a Neupert effect pattern, in which the optical/ultraviolet emission precedes the X-ray emission of a flare, whereas the X-ray flux is proportional to the integral of the optical flux.
- ID:
- ivo://CDS.VizieR/J/A+A/359/113
- Title:
- X-ray and IR study of Rho Oph dark cloud
- Short Name:
- J/A+A/359/113
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained two deep exposures of the {rho} Oph cloud core region with the ROSAT High Resolution Imager. The improved position accuracy (1"-6") with respect to previous recent X-ray observations (ROSAT PSPC, and ASCA) allows us to remove positional ambiguities for the detected sources. We also cross-correlate the X-ray positions with IR sources found in the ISOCAM survey of the same region at 6.7 and 14.3{mu}m, in addition to sources (optical and IR) known from ground-based observations, which are young stars (T Tauri stars, with and without circumstellar disks, and protostars). We thus obtain the best-studied sample of X-ray emitting stars in a star-forming region (63 X-ray sources detected, and 55 identified).
- ID:
- ivo://CDS.VizieR/J/ApJ/613/393
- Title:
- X-ray and radio sources in {rho} Oph Core A
- Short Name:
- J/ApJ/613/393
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A 96ks Chandra X-ray observation of {rho} Ophiuchus cloud core A detected 87 sources, of which 60 were identified with counterparts at other wavelengths. Simultaneous multifrequency Very Large Array (VLA) observations detected 31 radio sources at 6cm, of which 10 were also detected by Chandra. We report new radio detections of the optically invisible IR source WLY 2-11 and the faint H{alpha} emission line star Elias 24 (class II).
- ID:
- ivo://CDS.VizieR/J/A+A/454/595
- Title:
- X-ray emission of T Tau stars in Lupus 3
- Short Name:
- J/A+A/454/595
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- I present analysis results of an XMM-Newton observation of the Lupus 3 region that contains a high proportion of young low mass T Tauri stars in the Lupus star-forming complex. The detection of X-ray sources in 0.5 to 4.5-keV images of the Lupus 3 core was performed using the standard source detection method of the XMM-Newton Science Analysis Software. One hundred and two candidate X-ray sources were detected in the 30-arcmin diameter field-of-view of the EPIC cameras, of which 25 have visible or near-IR counterparts that are known as pre-main sequence stars.
- ID:
- ivo://CDS.VizieR/J/MNRAS/371/38
- Title:
- X-ray observations of the Galaxy center
- Short Name:
- J/MNRAS/371/38
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Galactic centre (GC) provides a unique laboratory for a detailed examination of the interplay between massive star formation and the nuclear environment of our Galaxy. Here, we present a 100-ks Chandra Advanced CCD Imaging Spectrometer (ACIS) observation of the Arches and Quintuplet star clusters. We also report on a complementary mapping of the dense molecular gas near the Arches cluster made with the Owens Valley Millimeter Array. We present a catalogue of 244 point-like X-ray sources detected in the observation.
- ID:
- ivo://CDS.VizieR/J/MNRAS/477/298
- Title:
- Young star clusters in nearby molecular clouds
- Short Name:
- J/MNRAS/477/298
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The SFiNCs (Star Formation in Nearby Clouds) project is an X-ray/infrared study of the young stellar populations in 22 star-forming regions with distances <~1kpc designed to extend our earlier MYStIX (Massive Young Star-Forming Complex Study in Infrared and X-ray) survey of more distant clusters. Our central goal is to give empirical constraints on cluster formation mechanisms. Using parametric mixture models applied homogeneously to the catalogue of SFiNCs young stars, we identify 52 SFiNCs clusters and 19 unclustered stellar structures. The procedure gives cluster properties including location, population, morphology, association with molecular clouds, absorption, age (Age_JX_), and infrared spectral energy distribution (SED) slope. Absorption, SED slope, and Age_JX_ are age indicators. SFiNCs clusters are examined individually, and collectively with MYStIX clusters, to give the following results. (1) SFiNCs is dominated by smaller, younger, and more heavily obscured clusters than MYStIX. (2) SFiNCs cloud-associated clusters have the high ellipticities aligned with their host molecular filaments indicating morphology inherited from their parental clouds. (3) The effect of cluster expansion is evident from the radius-age, radius-absorption, and radius-SED correlations. Core radii increase dramatically from ~0.08 to ~0.9pc over the age range 1-3.5Myr. Inferred gas removal time-scales are longer than 1Myr. (4) Rich, spatially distributed stellar populations are present in SFiNCs clouds representing early generations of star formation. An appendix compares the performance of the mixture models and non-parametric minimum spanning tree to identify clusters. This work is a foundation for future SFiNCs/MYStIX studies including disc longevity, age gradients, and dynamical modelling.
