The HP2 Survey - IV. The Pipe nebula : Effective dust temperatures in dense cores

14 pages, 22 figures. Accepted for publication in Astronomy & Astrophysics Reproduced with permission from Astronomy & Astrophysics. © 2018 ESOMulti-wavelength observations in the sub-millimeter regime provide information on the distribution of both the dust column density and the effective dust temperature in molecular clouds. In this study, we created high-resolution and high-dynamic-range maps of the Pipe nebula region and explored the value of dust-temperature measurements in particular towards the dense cores embedded in the cloud. The maps are based on data from the Herschel and Planck satellites, and calibrated with a near-infrared extinction map based on 2MASS observations. We have considered a sample of previously defined cores and found that the majority of core regions contain at least one local temperature minimum. Moreover, we observed an anti-correlation between column density and temperature. The slope of this anti-correlation is dependent on the region boundaries and can be used as a metric to distinguish dense from diffuse areas in the cloud if systematic effects are addressed appropriately. Employing dust-temperature data thus allows us to draw conclusions on the thermodynamically dominant processes in this sample of cores: External heating by the interstellar radiation field and shielding by the surrounding medium. In addition, we have taken a first step towards a physically motivated core definition by recognising that the column-densityerature anti-correlation is sensitive to the core boundaries. Dust-temperature maps therefore clearly contain valuable information about the physical state of the observed medium.Peer reviewe

VISION - Vienna survey in Orion. III. Young stellar objects in Orion A

38 pages, 25 figures, Accepted for publication by A&A. Reproduced with permission from Astronomy & Astrophysics. © 2018 ESOWe extend and refine the existing young stellar object (YSO) catalogs for the Orion A molecular cloud, the closest massive star-forming region to Earth. This updated catalog is driven by the large spatial coverage (18.3 deg^2, ~950 pc^2), seeing limited resolution (~0.7''), and sensitivity (Ks<19 mag) of the ESO-VISTA near-infrared survey of the Orion A cloud (VISION). Combined with archival mid- to far-infrared data, the VISTA data allow for a refined and more robust source selection. We estimate that among previously known protostars and pre-main-sequence stars with disks, source contamination levels (false positives) are at least ∼7% and ∼2.5%, respectively, mostly due to background galaxies and nebulosities. We identify 274 new YSO candidates using VISTA/Spitzer based selections within previously analyzed regions, and VISTA/WISE based selections to add sources in the surroundings, beyond previously analyzed regions. The WISE selection method recovers about 59% of the known YSOs in Orion A's low-mass star-forming part L1641, which shows what can be achieved by the all-sky WISE survey in combination with deep near-infrared data in regions without the influence of massive stars. The new catalog contains 2978 YSOs, which were classified based on the de-reddened mid-infrared spectral index into 188 protostars, 184 flat-spectrum sources, and 2606 pre-main-sequence stars with circumstellar disks. We find a statistically significant difference in the spatial distribution of the three evolutionary classes with respect to regions of high dust column-density, confirming that flat-spectrum sources are at a younger evolutionary phase compared to Class IIs, and are not a sub-sample seen at particular viewing angles.Peer reviewedFinal Accepted Versio

Gas absorption and dust extinction towards the Orion Nebula Cluster

B. Hasenberger, et al, 'Gas absorption and dust extinction towards the Orion Nebula Cluster', Astronomy & Astrophysics, 593, A7, 2016. The version of record is available online at DOI: 10.1051/0004-6361/201628517. Published by EDP Sciences. © ESO, 2016We characterise the relation between the gas and dust content of the interstellar medium towards young stellar objects in the Orion Nebula Cluster. X-ray observations provide estimates of the absorbing equivalent hydrogen column density N_H based on spectral fits. Near-infrared extinction values are calculated from intrinsic and observed colour magnitudes (J-H) and (H-K_s) as given by the VISTA Orion A survey. A linear fit of the correlation between column density and extinction values A_V yields an estimate of the N_H/A_V ratio. We investigate systematic uncertainties of the results by describing and (if possible) quantifying the influence of circumstellar material and the adopted extinction law, X-ray models, and elemental abundances on the N_H/A_V ratio. Assuming a Galactic extinction law with R_V=3.1 and solar abundances by Anders & Grevesse (1989), we deduce an N_H/A_V ratio of (1.39 +- 0.14) x 10^21 cm^-2 mag^-1 for Class III sources in the Orion Nebula Cluster where the given error does not include systematic uncertainties. This ratio is consistent with similar studies in other star-forming regions and approximately 31% lower than the Galactic value. We find no obvious trends in the spatial distribution of N_H/A_V ratios. Changes in the assumed extinction law and elemental abundances are demonstrated to have a relevant impact on deduced A_V and N_H values, respectively. Large systematic uncertainties associated with metal abundances in the Orion Nebula Cluster represent the primary limitation for the deduction of a definitive N_H/A_V ratio and the physical interpretation of these results.Peer reviewe

VISIONS:the VISTA Star Formation Atlas I. Survey overview

VISIONS is an ESO public survey of five nearby (d &lt; 500 pc) star-forming molecular cloud complexes that are canonically associated with the constellations of Chamaeleon, Corona Australis, Lupus, Ophiuchus, and Orion. The survey was carried out with the Visible and Infrared Survey Telescope for Astronomy (VISTA), using the VISTA Infrared Camera (VIRCAM), and collected data in the near-infrared passbands J (1.25 μm), H (1.65 μm), and KS (2.15 μm). With a total on-sky exposure time of 49.4h VISIONS covers an area of 650 deg2, it is designed to build an infrared legacy archive with a structure and content similar to the Two Micron All Sky Survey (2MASS) for the screened star-forming regions. Taking place between April 2017 and March 2022, the observations yielded approximately 1.15 million images, which comprise 19 TB of raw data. The observations undertaken within the survey are grouped into three different subsurveys. First, the wide subsurvey comprises shallow, large-scale observations and it has revisited the star-forming complexes six times over the course of its execution. Second, the deep subsurvey of dedicated high-sensitivity observations has collected data on areas with the largest amounts of dust extinction. Third, the control subsurvey includes observations of areas of low-to-negligible dust extinction. Using this strategy, the VISIONS observation program offers multi-epoch position measurements, with the ability to access deeply embedded objects, and it provides a baseline for statistical comparisons and sample completeness – all at the same time. In particular, VISIONS is designed to measure the proper motions of point sources, with a precision of 1 mas yr−1 or better, when complemented with data from the VISTA Hemisphere Survey (VHS). In this way, VISIONS can provide proper motions of complete ensembles of embedded and low-mass objects, including sources inaccessible to the optical ESA Gaia mission. VISIONS will enable the community to address a variety of research topics from a more informed perspective, including the 3D distribution and motion of embedded stars and the nearby interstellar medium, the identification and characterization of young stellar objects, the formation and evolution of embedded stellar clusters and their initial mass function, as well as the characteristics of interstellar dust and the reddening law

VISIONS:the VISTA Star Formation Atlas I. Survey overview

VISIONS is an ESO public survey of five nearby (d &lt; 500 pc) star-forming molecular cloud complexes that are canonically associated with the constellations of Chamaeleon, Corona Australis, Lupus, Ophiuchus, and Orion. The survey was carried out with the Visible and Infrared Survey Telescope for Astronomy (VISTA), using the VISTA Infrared Camera (VIRCAM), and collected data in the near-infrared passbands J (1.25 μm), H (1.65 μm), and KS (2.15 μm). With a total on-sky exposure time of 49.4h VISIONS covers an area of 650 deg2, it is designed to build an infrared legacy archive with a structure and content similar to the Two Micron All Sky Survey (2MASS) for the screened star-forming regions. Taking place between April 2017 and March 2022, the observations yielded approximately 1.15 million images, which comprise 19 TB of raw data. The observations undertaken within the survey are grouped into three different subsurveys. First, the wide subsurvey comprises shallow, large-scale observations and it has revisited the star-forming complexes six times over the course of its execution. Second, the deep subsurvey of dedicated high-sensitivity observations has collected data on areas with the largest amounts of dust extinction. Third, the control subsurvey includes observations of areas of low-to-negligible dust extinction. Using this strategy, the VISIONS observation program offers multi-epoch position measurements, with the ability to access deeply embedded objects, and it provides a baseline for statistical comparisons and sample completeness – all at the same time. In particular, VISIONS is designed to measure the proper motions of point sources, with a precision of 1 mas yr−1 or better, when complemented with data from the VISTA Hemisphere Survey (VHS). In this way, VISIONS can provide proper motions of complete ensembles of embedded and low-mass objects, including sources inaccessible to the optical ESA Gaia mission. VISIONS will enable the community to address a variety of research topics from a more informed perspective, including the 3D distribution and motion of embedded stars and the nearby interstellar medium, the identification and characterization of young stellar objects, the formation and evolution of embedded stellar clusters and their initial mass function, as well as the characteristics of interstellar dust and the reddening law

VISIONS: The VISTA Star Formation Atlas -- I. Survey overview

© The Authors 2023. Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0).VISIONS is an ESO public survey of five nearby (d < 500 pc) star-forming molecular cloud complexes that are canonically associated with the constellations of Chamaeleon, Corona Australis, Lupus, Ophiuchus, and Orion. The survey was carried out with VISTA, using VIRCAM, and collected data in the near-infrared passbands J, H, and Ks. With a total on-sky exposure time of 49.4 h VISIONS covers an area of 650 deg$^2$, and it was designed to build an infrared legacy archive similar to that of 2MASS. Taking place between April 2017 and March 2022, the observations yielded approximately 1.15 million images, which comprise 19 TB of raw data. The observations are grouped into three different subsurveys: The wide subsurvey comprises shallow, large-scale observations and has visited the star-forming complexes six times over the course of its execution. The deep subsurvey of dedicated high-sensitivity observations has collected data on the areas with the largest amounts of dust extinction. The control subsurvey includes observations of areas of low-to-negligible dust extinction. Using this strategy, the VISIONS survey offers multi-epoch position measurements, is able to access deeply embedded objects, and provides a baseline for statistical comparisons and sample completeness. In particular, VISIONS is designed to measure the proper motions of point sources with a precision of 1 mas/yr or better, when complemented with data from VHS. Hence, VISIONS can provide proper motions for sources inaccessible to Gaia. VISIONS will enable addressing a range of topics, including the 3D distribution and motion of embedded stars and the nearby interstellar medium, the identification and characterization of young stellar objects, the formation and evolution of embedded stellar clusters and their initial mass function, as well as the characteristics of interstellar dust and the reddening law.Peer reviewe

VISION - Vienna survey in Orion I. VISTA Orion A Survey

Stefan Meingast, et al., “VISION – Vienna survey in Orion”, Astronomy & Astrophysics, Vol. 587, March 2016. This version of record is available online at:https://www.aanda.org/articles/aa/abs/2016/02/aa26100-15/aa26100-15.html © ESO, 2016Orion A hosts the nearest massive star factory, thus offering a unique opportunity to resolve the processes connected with the formation of both low- and high-mass stars. Here we present the most detailed and sensitive near-infrared (NIR) observations of the entire molecular cloud to date. With the unique combination of high image quality, survey coverage, and sensitivity, our NIR survey of Orion A aims at establishing a solid empirical foundation for further studies of this important cloud. In this first paper we present the observations, data reduction, and source catalog generation. To demonstrate the data quality, we present a first application of our catalog to estimate the number of stars currently forming inside Orion A and to verify the existence of a more evolved young foreground population. We used the European Southern Observatory's (ESO) Visible and Infrared Survey Telescope for Astronomy (VISTA) to survey the entire Orion A molecular cloud in the NIR $J, H$, and $K_S$ bands, covering a total of $\sim$18.3 deg$^2$. We implemented all data reduction recipes independently of the ESO pipeline. Estimates of the young populations toward Orion A are derived via the $K_S$-band luminosity function. Our catalog (799995 sources) increases the source counts compared to the Two Micron All Sky Survey by about an order of magnitude. The 90% completeness limits are 20.4, 19.9, and 19.0 mag in $J, H$, and $K_S$, respectively. The reduced images have 20% better resolution on average compared to pipeline products. We find between 2300 and 3000 embedded objects in Orion A and confirm that there is an extended foreground population above the Galactic field, in agreement with previous work. The Orion A VISTA catalog represents the most detailed NIR view of the nearest massive star-forming region and provides a fundamental basis for future studies of star formation processes toward Orion.Peer reviewe

Submillimeter und Röntgen Beobachtungen des Interstellaren Mediums

Abweichender Titel laut Übersetzung der Verfasserin/des VerfassersZsfassung in dt. SpracheDiese Arbeit verwendet Daten, die von verschiedensten Teleskopen gewonnen worden sind, um die Eigenschaften des diffusen und dichten interstellaren Mediums und deren räumliche Veränderung über den gesamten Himmel hinweg abzuleiten. Aufgrund der Wellenlängenabhängigkeit der thermischen Staubemission und des Extinktionswirkungsquerschnittes werden der Submillimeter- und der Röntgenbereich gewählt, sodass unterschiedliche Bestandteile des lokalen interstellaren Medium beobachtet werden können. Durch die vor Kurzem veröffentlichen Ergebnisse des Satelliten Planck sind Staubemissionsmessungen für den gesamten Himmel verfügbar. Weiters wurde der Cluster des Orionnebels mit einer Reihe von hochauflösenden Instrumenten vermessen, was ideale Voraussetzungen für die Untersuchung des dichten interstellaren Mediums in dieser Region schafft. Um die Fülle an Daten zu nutzen, werden im Zuge der Analyse drei Vorgehensweisen verfolgt: Erstens wird die Röntgenemission von ausgedehnten Quellen mit den Mikrowellenbeobachtungen von Planck verglichen. Zweitens werden Röntgenspektren von Punktquellen verwendet, die die Ableitung der absorbierenden Gassäulendichte erlauben. Drittens werden Röntgen- und Submillimeterdaten des Orionnebels verglichen um das lokale Gas-zu-Staub-Verhältnis zu bestimmen. Der neue Planck-Datensatz erfordert eine detaillierte Untersuchung des Potentials und der Einschränkungen der angewandten Methoden, die in dieser Arbeit präsentiert wird. Die grundlegende Komplikation, dass die zu vergleichenden Daten typischerweise nicht dasselbe interstellare Material widerspiegeln, wird aufgezeigt. Gleichzeitig stellt es sich als schwierig heraus, die beiden Datensätze in einer solchen Weise zu beschränken, dass sie vergleichbar sind. Nichtsdestotrotz legen diese Analysen eine wesentliche räumliche Änderung der Beschaffenheit des interstellaren Mediums nahe, was der üblichen Annahme einheitlicher Eigenschaften über den gesamten Himmel hinweg widerspricht.This work employs data sets obtained by various telescopes to deduce properties of the diffuse and dense interstellar medium and their variation throughout the sky. Due to the wavelength dependency of thermal dust emission and the extinction cross section, the sub-millimetre and the X-ray range are chosen to trace different constituents of the local interstellar medium. With new results from the Planck satellite recently published, measurements of dust emission in the microwave regime are available across the entire sky. Furthermore, the Orion Nebula Cluster has been surveyed by a number of high-resolution instruments, providing ideal conditions to study the dense interstellar medium in this region. Three analysis approaches utilising this wealth of data are followed: First, X-ray emission from extended sources is compared to thermal dust emission as observed by Planck. Second, the X-ray spectra of point sources are used to derive numerical values for the absorbing gas column density. Third, X-ray and sub-millimetre data covering the Orion Nebula Cluster are compared in order to derive the local gas-to-dust ratio. The new Planck data set necessitates a detailed study of the potential and limitations of the involved methods which is presented in this work. The complication that the compared quantities typically do not correspond to the same interstellar material is revealed. Additionally, restricting the analysis in such a way that X-ray absorption and thermal dust emission are comparable parameters is found to constitute a difficult undertaking. Nevertheless, the conducted studies are suggestive of significant variations in the properties of the interstellar medium, contradicting the common assumption of uniform characteristics across the sky.7