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We present a study of the star formation histories of the Lupus I, III, and IV clouds using the Herschel 70-500 micron maps obtained by the Herschel Gould Belt Survey Key Project. By combining the new Herschel data with the existing Spitzer catalog we obtained an unprecedented census of prestellar sources and young stellar objects in the Lupus clouds, which allowed us to study the overall star formation rate (SFR) and efficiency (SFE). The high SFE of Lupus III, its decreasing SFR, and its large number of pre-main sequence stars with respect to proto- and prestellar sources, suggest that Lupus III is the most evolved cloud, and after having experienced a major star formation event in the past, is now approaching the end of its current star-forming cycle. Lupus I is currently undergoing a large star formation event, apparent by the increasing SFR, the large number of prestellar objects with respect to more evolved objects, and the high percentage of material at high extinction (e.g., above A_V=8 mag). Also Lupus IV has an increasing SFR; however, the relative number of prestellar sources is much lower, suggesting that its star formation has not yet reached its peak., Comment: 9 pages, 5 figures, accepted for publication in Astronomy and Astrophysics

The Mass loss of Evolved StarS (MESS) sample offers a selection of 78 Asymptotic Giant Branch (AGB) stars and Red Supergiants (RSGs) observed with the PACS photometer on-board Herschel at 70 and 160 {\mu}m. For most of these objects, the dusty AGB wind differs from spherical symmetry and the wind shape can be subdivided into four classes. In the present paper we concentrate on the influence of a companion on the morphology of the stellar wind. Literature was searched to find binaries in the MESS sample and these are subsequently linked to their wind-morphology class to assert that the binaries are not distributed equally among the classes. In the second part of the paper we concentrate on the circumstellar environment of the two prominent objects R Aqr and W Aql. Each shows a characteristic signature of a companion interaction with the stellar wind. For the symbiotic star R Aqr, PACS revealed two perfectly opposing arms which in part reflect the previously observed ring-shaped nebula in the optical. However, from the far-IR there is evidence that the emitting region is elliptical rather than circular. The outline of the wind of W Aql seems to follow a large Archimedean spiral formed by the orbit of the companion but also shows strong indications of an interaction with the interstellar medium. The nature of the companion of W Aql was investigated and the magnitude of the orbital period supports the size of the spiral outline., Comment: 14 pages, 9 figures, 5 tables

Context: Observations of transitional disks give us an understanding of the formation of planets and planetary systems such as our own. But care must be taken in the identification of such sources: the higher spatial resolution of the Herschel Space Observatory provides a new view on the origin of the far-infrared and sub-millimeter excesses observed. Aims: We review the nature of previously known transitional disks in the Chamaeleon I star-forming region with Herschel data. Methods: We analyze Herschel PACS and SPIRE images of the young star T54 together with ancillary images. We also analyze its spectral energy distribution and indications from optical and mid-infrared spectroscopy. Results: We detect extended emission in the PACS 70 \mu m image ~6" off source at a position angle of 196{\deg} from T54. The emission detected at longer wavelength (PACS 100, 160, SPIRE 250 and 350 \mu m) is also offset from the position of the star. This suggests that the excess observed in the far-infrared part of the SED is not fully associated with T54. Conclusions: Herschel images show that the far-infrared excess seen in T54 is not due to a transitional disk but to extended emission south-west of the source. The object still shows point-like and now downscaled excess at mid-infrared wavelengths, but its origin cannot be constrained without higher spatial resolution data. However, different indications point towards an evolved disk or extended unresolved emission close to the source., Comment: 5 pages, 2 figures, Accepted for publication in Astronomy & Astrophysics on 25 October 2012

We present new Herschel/PACS images at 70, 100, and 160 micron of the well-known, nearby, carbon-rich asymptotic giant branch star IRC+10216 revealing multiple dust shells in its circumstellar envelope. For the first time, dust shells (or arcs) are detected until 320 arcsec. The almost spherical shells are non-concentric and have an angular extent between 40 deg and 200 deg. The shells have a typical width of 5 arcsec - 8 arcsec, and the shell separation varies in the range of 10 arcsec - 35 arcsec, corresponding to 500-1700 yr. Local density variations within one arc are visible. The shell/intershell density contrast is typically 4, and the arcs contain some 50% more dust mass than the smooth envelope. The observed (nested) arcs record the mass-loss history over the past 16 000 yr, but Rayleigh-Taylor and Kelvin-Helmholtz instabilities in the turbulent astropause and astrosheath will erase any signature of the mass-loss history for at least the first 200 000 yr of mass loss. Accounting for the bowshock structure, the envelope mass around IRC+10216 contains >2Msun of gas and dust mass. It is argued that the origin of the shells is related to non-isotropic mass-loss events and clumpy dust formation., Comment: 8 pages, published in Astronomy & Astrophysics

Aims. We analyze the surroundings of HD 97300, one of two intermediate-mass stars in the Chamaeleon I star-forming region. The star is known to be surrounded by a conspicuous ring of polycyclic aromatic hydrocarbons (PAHs). Methods. We present infrared images taken with Herschel and Spitzer using 11 different broad-band filters between 3.6 um and 500 um. We compare the morphology of the emission using cuts along different position angles. We construct spectral energy distributions, which we compare to different dust models, and calculate dust temperatures. We also derive opacity maps and analyze the density structure of the environment of HD 97300. Results. We find that HD 97300 has no infrared excess at or below 24 um, confirming its zero-age main-sequence nature. The morphology of the ring is very similar between 3.6 um and 24 um. The emission at these wavelengths is dominated by either PAH features or PAH continuum. At longer wavelengths, only the northwestern part of the ring is visible. A fit to the 100-500 um observations suggests that the emission is due to relatively warm (~26 K) dust. The temperature gradually decreases with increasing distance from the ring. We find a general decrease in the density from north to south, and an approximate 10% density increase in the northeastern part of the ring. Conclusions. Our results are consistent with the theory that the ring around HD 97300 is essentially a bubble blown into the surrounding interstellar matter and heated by the star., Comment: 6 pages, 3 figures, accepted for publication in A&A

S-type AGB stars are thought to be in the transitional phase between M-type and C-type AGB stars. Because of their peculiar chemical composition, one may expect a strong influence of the stellar C/O ratio on the molecular chemistry and the mineralogy of the circumstellar dust. In this paper, we present a large sample of 87 intrinsic galactic S-type AGB stars, observed at infrared wavelengths with the Spitzer Space Telescope, and supplemented with ground-based optical data. On the one hand, we derive the stellar parameters from the optical spectroscopy and photometry, using a grid of model atmospheres. On the other, we decompose the infrared spectra to quantify the flux-contributions from the different dust species. Finally, we compare the independently determined stellar parameters and dust properties. For the stars without significant dust emission, we detect a strict relation between the presence of SiS absorption in the Spitzer spectra and the C/O ratio of the stellar atmosphere. These absorption bands can thus be used as an additional diagnostic for the C/O ratio. For stars with significant dust emission, we define three groups, based on the relative contribution of certain dust species to the infrared flux. We find a strong link between group-membership and C/O ratio. We show that these groups can be explained by assuming that the dust-condensation can be cut short before silicates are produced, while the remaining free atoms and molecules can then form the observed magnesium sulfides or the carriers of the unidentified 13 and 20 micron features. Finally, we present the detection of emission features attributed to molecules and dust characteristic to C-type stars, such as molecular SiS, hydrocarbons and magnesium sulfide grains. We show that we often detect magnesium sulfides together with molecular SiS and we propose that it is formed by a reaction of SiS molecules with Mg., Comment: Accepted for publication in A&A

This study attempts to establish a link between the reasonably well known nature of the progenitor of SN2011fe and its surrounding environment. This is done with the aim of enabling the identification of similar systems in the vast majority of the cases, when distance and epoch of discovery do not allow a direct approach. To study the circumstellar environment of SN2011fe we have obtained high-resolution spectroscopy of SN2011fe on 12 epochs, from 8 to 86 days after the estimated date of explosion, targeting in particular at the time evolution of CaII and NaI. Three main absorption systems are identified from CaII and NaI, one associated to the Milky Way, one probably arising within a high-velocity cloud, and one most likely associated to the halo of M101. The Galactic and host galaxy reddening, deduced from the integrated equivalent widths (EW) of the NaI lines are E(B-V)=0.011+/-0.002 and E(B-V)=0.014+/-0.002 mag, respectively. The host galaxy absorption is dominated by a component detected at the same velocity measured from the 21-cm HI line at the projected SN position (~180 km/s). During the ~3 months covered by our observations, its EW changed by 15.6+/-6.5 mA. This small variation is shown to be compatible with the geometric effects produced by therapid SN photosphere expansion coupled to the patchy fractal structure of the ISM. The observed behavior is fully consistent with ISM properties similar to those derived for our own Galaxy, with evidences for structures on scales <100 AU. SN2011fe appears to be surrounded by a "clean" environment. The lack of blue-shifted, time-variant absorption features is fully consistent with the progenitor being a binary system with a main-sequence, or even another degenerate star., Comment: 12 pages, 6 figures, submitted to Astronomy and Astrophysics

Far-infrared Herschel/PACS images at 70 and 160 micron of a sample of 78 Galactic evolved stars are used to study the (dust) emission structures, originating from stellar wind-ISM interaction. In addition, two-fluid hydrodynamical simulations of the coupled gas and dust in wind-ISM interactions are used to compare with the observations. Four distinct classes of wind-ISM interaction (i.e. "fermata", "eyes", "irregular", and "rings") are identified and basic parameters affecting the morphology are discussed. We detect bow shocks for ~40% of the sample and detached rings for ~20%. De-projected stand-off distances (R_0) -- defined as the distance between the central star and the nearest point of the interaction region -- of the detected bow shocks ("fermata" and "eyes") are derived from the PACS images and compared to previous results, model predictions and the simulations. All observed bow shocks have stand-off distances smaller than 1 pc. Observed and theoretical stand-off distances are used together to independently derive the local ISM density. Both theoretical (analytical) models and hydrodynamical simulations give stand-off distances for adopted stellar properties that are in good agreement with the measured de-projected stand-off distance of wind-ISM bow shocks. The possible detection of a bow shock -- for the distance limited sample -- appears to be governed by its physical size as set roughly by the stand-off distance. In particular the star's peculiar space velocity and the density of the ISM appear decisive in detecting emission from bow shocks or detached rings. Tentatively, the "eyes" class objects are associated to (visual) binaries, while the "rings" generally appear not to occur for M-type stars, only for C or S-type objects that have experienced a thermal pulse., Comment: 29 pages, 15 figures. Accepted for publication in A&A

We performed a mid-infrared imaging survey of evolved stars in order to study the dust distribution in circumstellar envelopes around these objects and to better understand the mass-loss mechanism responsible for the formation of these envelopes. During this survey, we resolved for the first time the circumstellar environment of IRAS 17163-3907 (hereinafter IRAS17163), which is one of the brightest objects in the mid-infrared sky, but is surprisingly not well studied. Our aim is to determine the evolutionary status of IRAS 17163 and study its circumstellar environment in order to understand its mass-loss history. We obtained diffraction-limited images of IRAS 17163 in the mid-infrared using VISIR on the VLT. Optical spectra of the object allowed us to determine its spectral type and estimate its distance via the presence of diffuse interstellar bands. We show that IRAS 17163 is a Post-Red Supergiant, possibly belonging to the rare class of Yellow Hypergiants, and is very similar to the well studied object IRC +10420. Our mid-infrared images of IRAS 17163 are the first direct images of this bright mid-infrared source. These images clearly show the presence of a double dusty detached shell around the central star, due to successive ejections of material with a timescale of the order of 400 years and a total circumstellar mass larger than 4 M$_{\odot}$. This indicates that non quiescent mass-loss occurs during this phase of stellar evolution., Comment: Accepted for publication in Astronomy & Astrophysics letters

We study the effects of local environmental conditions affecting the diffuse interstellar band (DIB) carriers within the Upper Scorpius subgroup of the Sco OB2 association. We obtained optical spectra with FEROS, and measured the equivalent widths of five DIBs (at 5780, 5797, 6196, 6379, and 6613 Angstrom) as well as those of absorption lines of di-atomic molecules (CH, CH+, CN) and atoms (KI, CaI) towards 89 targets in the direction of Upper Scorpius. We construct a simple radiative transfer and chemical network model of the diffuse interstellar medium (ISM) sheet in front of Upp Sco to infer the effective radiation field. Both the interstellar radiation field strength, I_UV, and the molecular hydrogen fraction, f_H2, have been derived for 55 sightlines probing the Upp Sco ISM. We discuss the relations between DIB strengths, CH and CH+ line strengths, E(B-V), I_UV, and f_H2. The ratio between the 5780 and 5797 DIBs reveals a (spatial) dependence on the local environment in terms of cloud density and exposure to the interstellar radiation field, reflecting the molecular nature of these DIB carriers., Comment: accepted for publication in A&A. 19 pages, 25 figures main paper. 26 pages appendix. v2. Minor revisions

The origin of the narrow optical emission bands seen toward the Red Rectangle is not yet understood. In this paper we investigate further the proposal that these are due to luminescence of large carbonaceous molecules. Polarised signals of several percent could be expected from certain asymmetric molecular rotators. The ESPaDOnS echelle spectrograph mounted at the CFHT was used to obtain high-resolution optical spectropolarimetric data of the Red Rectangle nebular emission. The RRBs at 5800, 5850, and 6615 Angstrom are detected in spectra of the nebular emission 7" and 13" North-East from the central star. The 5826 and 6635 Angstrom RRB are detected only at the position nearest to the central star. For both positions the Stokes Q and U spectra show no unambiguous polarisation signal in any of the RRBs. We derive an upper limit of 0.02% line polarisation for these RRBs. A tentative feature with peak polarisation of 0.05% is seen for the 5800 RRB at 7" offset. However, the Null spectra suggest that this may be an instrumental artifact. The lack of a clear polarisation signal for the five detected RRBs implies that, if the emission is due to luminescence of complex organics, these gas-phase molecular carriers are likely to have a high degree of symmetry, as they do not exhibit a Q-branch in their rotational profile, although this may be modified by statistical effects., Comment: 5 pages, 4 figures, accepted for A&A

Context. The identification of the carriers of diffuse interstellar bands (DIBs) remains one of the long-standing mysteries in astronomy. The detection of a polarisation signal in a DIB profile can be used to distinguish between a dust or gas-phase carrier. The polarisation profile can give additional information on the grain or molecular properties of the absorber. In order to detect and measure the linear and circular polarisation of the DIBs we observed reddened lines of sight showing continuum polarisation. For this study we selected two stars HD 197770 and HD 194279. We used high-resolution (R~64.000) spectropolarimetry in the wavelength range from 3700 to 10480 Angstrom with the ESPaDOnS echelle spectrograph mounted at the CFHT. Results. High S/N and high resolution Stokes V (circular), Q and U (linear) spectra were obtained. We constrained upper limits by a factor of 10 for previously observed DIBs. Furthermore, we analysed ~30 additional DIBs for which no spectropolarimetry data has been obtained before. This included the 9577 A DIB and the 8621 A DIB. Conclusions. The lack of polarisation in 45 DIB profiles suggests that none of the absorption lines is induced by a grain-type carrier. The strict upper limits, less than ~0.01%, derived for the observed lines-of-sight imply that if DIBs are due to gas-phase molecules these carriers have polarisation efficiencies which are at least 6 times, and up to 300 times, smaller than those predicted for grain-related carriers., Comment: 6 pages + 13 pages online material, submitted to A&A

By tracing the distribution of cool dust in the extended envelopes of post-AGB stars and (proto)-planetary nebulae ((P)PNe) we aim to recover, or constrain, the mass loss history experienced by these stars in their recent past. The Far-Infrared Surveyor (FIS) instrument on board the AKARI satellite was used to obtain far-infrared maps for a selected sample of post-AGB stars and (P)PNe. We derived flux densities (aperture photometry) for 13 post-AGB stars and (P)PNe at four far-infrared wavelengths (60, 90, 140, and 160 um). Radial (azimuthally averaged) profiles are used to investigate the presence of extended emission from cool dust. No (detached) extended emission is detected for any target in our sample at levels significant with respect to background and cirrus emission. Only IRAS 21046+4739 reveals tentative excess emission between 30 and 130". Estimates of the total dust and gas mass from the obtained maps indicate that the envelope masses of these stars should be large in order to be detected with the AKARI FIS. Imaging with higher sensitivity and higher spatial resolution is needed to detect and resolve, if present, any cool compact or extended emission associated with these evolved stars., Comment: accepted for publication in The Astronomical Journal (16 pages, 3 figures and 4 tables)

MESS (Mass-loss of Evolved StarS) is a Guaranteed Time Key Program that uses the PACS and SPIRE instruments on board the Herschel Space Observatory to observe a representative sample of evolved stars, that include asymptotic giant branch (AGB) and post-AGB stars, planetary nebulae and red supergiants, as well as luminous blue variables, Wolf-Rayet stars and supernova remnants. In total, of order 150 objects are observed in imaging and about 50 objects in spectroscopy. This paper describes the target selection and target list, and the observing strategy. Key science projects are described, and illustrated using results obtained during Herschel's science demonstration phase. Aperture photometry is given for the 70 AGB and post-AGB stars observed up to October 17, 2010, which constitutes the largest single uniform database of far-IR and sub-mm fluxes for late-type stars., Comment: A&A accepted

AIMS. In this work we explore the possibility of using the fast expansion of a Type Ia supernova photosphere to detect extra-galactic ISM column density variations on spatial scales of ~100 AU on time scales of a few months. METHODS. We constructed a simple model which describes the expansion of the photodisk and the effects of a patchy interstellar cloud on the observed equivalent width of Na I D lines. Using this model we derived the behavior of the equivalent width as a function of time, spatial scale and amplitude of the column density fluctuations. RESULTS. The calculations show that isolated, small (<100 AU) clouds with Na I column densities exceeding a few 10^11 cm^-2 would be easily detected. In contrast, the effects of a more realistic, patchy ISM become measurable in a fraction of cases, and for peak-to-peak variations larger than ~10^12 cm^-2 on a scale of 1000 AU. CONCLUSIONS. The proposed technique provides a unique way to probe the extra-galactic small scale structure, which is out of reach for any of the methods used so far. The same tool can also be applied to study the sub-AU Galactic ISM structure., Comment: 6 pages, 3 figures. Accepted for publication in Astronomy & Astrophysics

Aims. Supernovae offer the unique possibility to probe diffuse extra-galactic sightlines via observation of the optical transitions of atoms, molecules and the diffuse interstellar bands (DIBs). Through optical spectroscopy the presence of (complex) molecules in distant galaxies can be established. Methods. High resolution optical (3300 -- 6800 Angstrom) spectra of SN2006X at different phase obtained with UVES on the VLT were reduced and analysed. Results. In addition to previously detected atomic (NaI and CaII) and molecular (CN) transitions we present detections of DIBs (6196, 6283 Angstrom), diatomic molecules (CH, CH+) and neutral atoms (CaI) in the spectra of SN2006X taken at different phases (at 2 days before and 14 and 61 days after the brightness maximum). An analysis of the absorption profiles shows no variation between phases in the abundance, nor the central velocities (within 3-sigma error bars) of the (dense) gas tracers (CH, CH+ and CaI) and the DIBs. This is consistent with the conclusion in the literature that SN2006X exploded behind a dense interstellar cloud (inferred from strong atomic sodium and calcium lines and CN transitions) which caused strong photometric reddening but whose material was not directly affected by the supernova explosion. The CH and CN column densities correspond to a reddening of one magnitude following the Galactic correlation derived previously. The 6196 and 6283 lines detected in the M100 ISM are under-abundant by factor of 2.5 to 3.5 (assuming a visual extinction of ~2 mag) compared to the average Galactic ISM relationship. Upper limits for 6379 and 6613 DIBs show that these are at least a factor of seven weaker. Therefore, the Galactic DIB-reddening relation does not seem to hold in M100, although the lower gas-to-dust ratio may further reduce this discrepancy., Comment: 4 pages, including 7 figures, accepted for A&A Letters

We investigate the diffuse interstellar band (DIB) spectrum in the interstellar medium of M31. The DEIMOS spectrograph of the W. M. Keck observatory was used to make optical spectroscopic observations of two supergiant stars, MAG 63885 and MAG 70817, in the vicinity of the OB78 association in M31 where the metallicity is approximately equal to solar. The 5780, 5797, 6203, 6283 and 6613 DIBs are detected in both sightlines at velocities matching the M31 interstellar Na I absorption. The spectra are classified and interstellar reddenings are derived for both stars. Diffuse interstellar band (DIB) equivalent widths and radial velocities are presented. The spectrum of DIBs observed in M31 towards MAG 63885 is found to be similar to that observed in the Milky Way. Towards MAG 70817 the DIB equivalent widths per unit reddening are about three times the Galactic average. Compared to observations elsewhere in the Universe, relative to reddening the M31 ISM in the vicinity of OB78 is apparently a highly favourable environment for the formation of DIB carriers.

In this work we present the results of a systematic search for diffuse bands (DBs, hereafter) in the circumstellar envelopes of a carefully selected sample of post-AGB stars. We concentrated on the analysis of 9 of the DBs most commonly found in the interstellar medium. The strength of these features is determined using high resolution optical spectroscopy and the results obtained are compared with literature data on field stars affected only by interstellar reddening. Based on the weak features observed in the subsample of post-AGB stars dominated by circumstellar reddening we conclude that the carrier(s) of these DBs must not be present in the circumstellar environment of these sources, or at least not under the excitation conditions in which DBs are formed. The conclusion is applicable to all the post-AGB stars studied, irrespective of the dominant chemistry or the spectral type of the star considered. A detailed radial velocity analysis of the features observed in individual sources confirms this result, as the Doppler shifts measured are found to be consistent with an interstellar origin., Comment: Accepted for A&A

We present here the first detailed study of a giant radio galaxy of the Fat-Double type. The lobes of the double radio galaxy SGRS J0515-8100 have transverse widths that are 1.3 times their extent from the center, their surface brightness is the lowest among known giant radio sources and the lobes have relatively steep radio spectra. We infer that these wide lobes were created as a result of a highly variable and intermittent jet whose axis direction also varied significantly: the Fat-Double lobes in this giant radio source are a result of the ejection and deposition of synchrotron plasma over a wide range of angles over time rather than the expansion of relic lobes. Additionally, the optical host shows evidence for an ongoing galaxy-galaxy interaction. SGRS J0515-8100 supports the hypothesis that interactions with companions might perturb the inner accretion disk that produces and sustains the jets at the centers of active galactic nuclei. As a result, it appears unnecessary to invoke black-hole coalescence to explain such morphologies, implying that the corresponding event rates predicted for gravitational wave detectors may be overestimates., Comment: Accepted for publication in Apj, 10 figures