Multiple populations in young clusters detected by Gaia.

The second release of Gaia is revolutionizing the study of star formation and young clusters. In this talk I discussed the potential in detecting multiple populations in young clusters, and the importance of a membership well defined as a starting point. I presented, as an example, the results on the multiple population of one of the closest low-mass star forming region, the Chamaeloen I. Using the Gaia data we found the region to be at slightly higher distance than previously thought. We confirmed the presence of two populations with a peculiar spatial distribution, which might be influenced by the filamentary molecular cloud present in the region. Presenting the method applied to find kinematically the multiple populations, I discussed the effect on the results of taking into account the correlations between parallaxes and proper motions. I finally presented the impact of the refined distance of young stars and clusters using the Gaia data on other fields of star formation, e.g. the study of the evolution of protoplanetary disks and the disk structure

Multi-wavelength studies of protoplanetary discs

The early evolutionary stages of a pre-main sequence star are characterised by the formation of a dense accretion disc. These discs provide the environment and material in and from which planets are expected to form. At this epoch circumstellar material is accreting onto the central star, while small dust grains in the disc interior coagulate into larger objects and gravitationally settle into the mid-plane. These are the first steps of planet formation. The study of the dust properties (e.g. grain size distribution, dissipation timescale) in protoplanetary discs is then fundamental to understand how planets form. In this thesis I present three works aimed at studying the formation, dissipation and long term evolution of protoplanetary discs, respectively. The first project investigates the properties of the young binary system Haro~6-10. I present the results of multi-wavelength high spatial resolution observations of Haro 6-10 aimed at characterising the large- and small-scale structures of the binary system. The second project is a combined infrared (Spitzer/IRAC) and X-ray (Chandra/ACIS) survey of the OB association IC~1795. This program is aimed at studying the evolution of protoplanetary discs in regions of massive star formation. The last project is the deepest single dish millimetre survey of debris discs around solar-type stars to date. The aim of this work is to study the evolution of the debris dust mass with time and to characterise the structure of these discs

Herschel far-infrared observations of the Carina Nebula Complex. - III: Detailed cloud structure and feedback effects

The Carina Nebula complex (CNC) represents one of the most massive star-forming regions in our Galaxy and shows strong feedback from the high massive stars. We use our Herschel FIR observations to study the properties of the clouds over the entire area of the CNC. The good angular resolution of the Herschel maps corresponds to physical scales of 0.1 - 0.4 pc, and allows us to analyze the small-scale structures of the clouds. The full extent of the CNC was mapped with PACS and SPIRE from 70 to 500 micron. We determine temperatures and column densities at each point in this maps by modeling the observed FIR SEDs. We also derive a map showing the strength of the UV field. We investigate the relation between the cloud properties and the spatial distribution of the high-mass stars, and compute total cloud masses for different density thresholds. Our Herschel maps resolve, for the first time, the small-scale structure of the dense clouds. Several particularly interesting regions, including the prominent pillars south of eta Car, are analyzed in detail. We compare the cloud masses derived from the Herschel data to previous mass estimates based on sub-mm and molecular line data. Our maps also reveal a peculiar "wave"-like pattern in the northern part of the Carina Nebula. Finally, we characterize two prominent cloud complexes at the periphery of our Herschel maps, which are probably molecular clouds in the Galactic background. We find that the density and temperature structure of the clouds in most parts of the CNC is dominated by the strong feedback from the numerous massive stars, rather than random turbulence. Comparing the cloud mass and the star formation rate derived for the CNC to other Galactic star forming regions suggests that the CNC is forming stars in an particularly efficient way. We suggest this to be a consequence of triggered star formation by radiative cloud compression.Comment: Accepted for publication in Astronomy & Astrophysics. A high quality preprint is available at http://www.usm.uni-muenchen.de/people/preibisch/publications.htm

Detection of new O-type stars in the obscured stellar cluster Tr 16-SE in the Carina Nebula with KMOS

The Carina Nebula harbors a large population of high-mass stars, including at least 75 O-type and Wolf-Rayet stars, but the current census is not complete since further high-mass stars may be hidden in or behind the dense dark clouds that pervade the association. With the aim of identifying optically obscured O- and early B-type stars in the Carina Nebula, we performed the first infrared spectroscopic study of stars in the optically obscured stellar cluster Tr 16-SE, located behind a dark dust lane south of eta Car. We used the integral-field spectrograph KMOS at the ESO VLT to obtain H- and K-band spectra with a resolution of R sim 4000 (Delta lambda sim 5 A) for 45 out of the 47 possible OB candidate stars in Tr 16-SE, and we derived spectral types for these stars. We find 15 stars in Tr 16-SE with spectral types between O5 and B2 (i.e., high-mass stars with M >= 8 Msun, only two of which were known before. An additional nine stars are classified as (Ae)Be stars (i.e., intermediate-mass pre-main-sequence stars), and most of the remaining targets show clear signatures of being late-type stars and are thus most likely foreground stars or background giants unrelated to the Carina Nebula. Our estimates of the stellar luminosities suggest that nine of the 15 O- and early B-type stars are members of Tr 16-SE, whereas the other six seem to be background objects. Our study increases the number of spectroscopically identified high-mass stars (M >= 8 Msun) in Tr 16-SE from two to nine and shows that Tr 16-SE is one of the larger clusters in the Carina Nebula. Our identification of three new stars with spectral types between O5 and O7 and four new stars with spectral types O9 to B1 significantly increases the number of spectroscopically identified O-type stars in the Carina Nebula.Comment: Accepted for publication in Astronomy & Astrophysic

A Herschel view of IC 1396 A: Unveiling the different sequences of star formation

The IC1396A globule in the young cluster Tr37, hosting many young stars and protostars, is assumed to be a site of triggered star formation. We mapped IC1396A with Herschel/PACS at 70 and 160 micron. The Herschel maps trace in great detail the very embedded protostellar objects and the structure of the cloud. PACS data reveal a previously unknown Class 0 object (IC1396A-PACS-1) located behind the ionization front. IC1396A-PACS-1 is not detectable with Spitzer, but shows marginal X-ray emission. The data also allowed to study three of the Class I intermediate-mass objects within the cloud. We derived approximate cloud temperatures to study the effect and potential interactions between the protostars and the cloud. The Class 0 object is associated with the densest and colder part of IC1396A. Heating in the cloud is dominated by the winds and radiation of the O6.5 star HD 206267 and, to a lesser extent, by the effects of the Herbig Ae star V 390 Cep. The surroundings of the Class I and Class II objects embedded in the cloud also appear warmer than the sourceless areas, although most of the low-mass objects cannot be individually extracted due to distance and beam dilution. The observations suggest that at least two episodes of star formation have occurred in IC1396A. One would have originated the known, ~1 Myr-old Class I and II objects in the cloud, and a new wave of star formation would have produced the Class 0 source at the tip of the brigth-rimmed cloud. From its location and properties, IC1396A-PACS-1 is consistent with triggering via radiative driven implosion (RDI) induced by HD 206267. The mechanisms behind the formation of the more evolved population of Class I/II/III objects in the cloud are uncertain. Heating of most of the remaining cloud by Class I/Class II objects and by HD 206267 itself may preclude further star formation in the region.Comment: Accepted by A&A, 9 pages, 5 figure

IRAM and Gaia views of multi-episodic star formation in IC1396A:The origin and dynamics of the Class 0 protostar at the edge of an HII region

(Abridged) IC1396A is a cometary globule containing the Class 0 source IC1396A-PACS-1. We use IRAM 30m and Gaia DR2 data to explore the star-formation history of IC1396A and investigate the possibilities of triggered star formation. IRAM and Herschel continuum data reveal dust temperatures and column densities. Heterodyne data reveal the velocity structure of the gas. Gaia DR2 proper motions for the stars complete the kinematics of the region. IC1396A-PACS-1 shows molecular emission similar to a hot corino with warm carbon chain chemistry, and is surrounded by gas at velocities significantly different from the velocities of the Tr37 cluster. Combining the velocity, column density, and temperature information and Gaia DR2 kinematics, we confirm that IC1396A has suffered various episodes of star formation. IC1396A-PACS-1 is probably the last intermediate-mass protostar that will form within IC1396A, showing evidence of triggering by radiative driven implosion. Chemical signatures place IC1396A-PACS-1 among the youngest protostars known. Gaia DR2 data reveal velocities in the plane of the sky $sim$4km/s for IC1396A with respect to Tr37. The total velocity difference (8 km/s) between the Tr37 cluster and IC1396A is too small for IC1396A to have undergone substantial rocket acceleration, which imposes constraints on the distance to the ionizing source in time and the possibilities of triggered star formation. The three stellar populations in the globule reveal that objects located within relatively close distances (<0.5pc) can be formed in various episodes within a $sim$1-2 Myr period. We expect substantial differences in initial conditions for the resulting objects and their protoplanetary disks, which may affect their evolution. Finally, evidence for short-range feedback from the embedded protostars and, in particular, the A-type star V390 Cep is also observed

The STAR-MELT Python package for emission line analysis of YSOs

We introduce the STAR-MELT Python package that we developed to facilitate the analysis of time-resolved emission line spectroscopy of young stellar objects. STAR-MELT automatically extracts, identifies and fits emission lines. We summarise our analysis methods that utilises the time domain of high-resolution stellar spectra to investigate variability in the line profiles and corresponding emitting regions. This allows us to probe the innermost disc and accretion structures of YSOs. Local temperatures and densities can be determined using Boltzmann statistics, the Saha equation, and the Sobolev large velocity gradient approximation. STAR-MELT allows for new results to be obtained from archival data, as well as facilitating timely analysis of new data as it is obtained. We present the results of applying STAR-MELT to three YSOs, using spectra from UVES, XSHOOTER, FEROS, HARPS, and ESPaDOnS. We demonstrate what can be achieved for data with disparate time sampling, for stars with different inclinations and variability types. For EX Lupi, we confirm the presence of a localised and stable stellar-surface hotspot associated with the footprint of the accretion column. For GQ Lupi A, we find that the maximum infall rate from an accretion column is correlated with lines produced in the lowest temperatures. For CVSO109 we investigate the rapid temporal variability of a redshifted emission wing, indicative of rotating and infalling material in the inner disc. Our results show that STAR-MELT is a useful tool for such analysis, as well as other applications for emission lines.<br/

Star formation in IC1396:Kinematics and subcluster structure revealed by Gaia

Aims. We investigate the star formation history of the IC1396 region by studying its kinematics and completing the population census. Methods. We used multiwavelength data, combining optical spectroscopy to identify and classify new members and near-infrared photometry to trace shocks, jets, and outflows as well as the interactions between the cluster members and the cloud. We also used Gaia EDR3 data to identify new potential members in the multidimensional proper motion and parallax space. Results. The revised Gaia EDR3 distance is 925±73 pc, slightly closer than previously obtained with DR2. The Gaia data reveal four distinct subclusters in the region. These subclusters are consistent in distance but display differences in proper motion. This result, with their age differences, hints toward a complex and varied star formation history. The Gaia data also unveil intermediate-mass objects that tend to evade spectroscopic and disk surveys. Our analysis has allowed us to identify 334 new members. We estimate an average age of ∼4 Myr, confirming previous age estimates. With the new members added to our study, we estimate a disk fraction of 28%, lower than previous values, due to our method detecting mainly new, diskless, intermediate-mass stars. We find age differences between the subclusters, which offers evidence of a complex star formation history with different episodes of star formation

ANTIFUNGAL ACTIVITY OF ROSEMARY ESSENTIAL OIL AGAINST FOODSTUFFS FUNGI

The essential oils are well known for their antibacteric, antomycotic and insecticide effects. In this research the antomycotic activity of Rosemary essential oil has been tested in vitro versus different moulds, common contaminants of food and feed, as Aspergillus flavus, Aspergillus ochraceus, Aspergillus niger, Aspergillus ustus, Penicillium expansum, Penicillium aurantio-griseum, Fusarium moniliforme. The Rosemary essential oil tested (produced in Sardegna, Italy) shows a different efficacy against various moulds and his activity seems to be produced by borneol, &alpha;-pinene, eucalyptol, camphor and limonene. Aspergillus and Penicillium are the genus showing an important inhibition of their development in vitro. Rosemary essential oil for these natural properties can be used as antimycotic additive to extended shelf-life of many foodstuffs

Protostars and stars in the Coronet cluster: Age, evolution, and cluster structure

We present new optical spectroscopy with FLAMES/VLT, near-IR imaging with HAWK-I/VLT, and 870 micron mapping with APEX/LABOCA of the Coronet cluster. The optical data allow to estimate spectral types, extinction and the presence of accretion in 6 more M-type members, in addition to the 12 that we had previously studied. The submillimeter maps and near-IR data reveal the presence of nebular structures and high extinction regions, which are in some cases associated to known IR, optical, and X-ray sources. Most star formation is associated to two elongated structures crossing in the central part of the cluster. Placing all the 18 objects with known spectral types and extinction in the HR diagram suggests that the cluster is younger than previously thought (<2 Myr, and probably ~0.5-1 Myr). The new age estimate is in agreement with the evolutionary status of the various protostars in the region and with its compactness (<1.3 pc across), but results in a conflict with the low disk and accretion fraction (only 50-65% of low-mass stars appear to have protoplanetary disks, and most transitional and homologously depleted disks are consistent with no accretion) and with the evolutionary features observed in the mid-IR spectra and spectral energy distributions of the disks.Comment: 30 pages, 9 figures, 6 tables, ApJ in pres