Many aspects of the evolutionary phase in which Asymptotic Giant Branch stars (AGB stars) are in transition to become Planetary Nebulae (PNe) are still poorly understood. An important question is how the circumstellar envelopes of AGB stars switch from spherical symmetry to the axially symmetric structures frequently observed in PNe. In many cases there is clear evidence that the shaping of the circumstellar envelopes of PNe is linked to the formation of jets/collimated winds and their interaction with the remnant AGB envelope. Because of the short evolutionary time, objects in this phase are rare, but their identification provides valuable probes for testing evolutionary models. We have observed (sub)millimeter CO rotational transitions with the APEX telescope in a small sample of stars hosting high-velocity OH and water masers. These targets are supposed to have recently left the AGB, as indicated by the presence of winds traced by masers, with velocities larger than observed during that phase. We have carried out observations of several CO lines, ranging from J=2-1 up to J=7-6. In IRAS 15452-5459 we detect a fast molecular outflow in the central region of the nebula and estimate a mass-loss rate between 1.2x10^{-4} Msun yr^{-1} (assuming optically thin emission) and 4.9x10^{-4} Msun yr^{-1} (optically thick emission). We model the SED of this target taking advantage of our continuum measurement at 345 GHz to constrain the emission at long wavelengths. For a distance of 2.5 kpc, we estimate a luminosity of 8000 Lsun and a dust mass of 0.01 Msun. Through the flux in the [CII] line (158 um), we calculate a total mass of about 12 Msun for the circumstellar envelope, but the line is likely affected by interstellar contamination.

We have analysed optical spectra of BL Lacertae, the prototype of its class, to verify the presence and possible flux variations of its broad Ha line. We used the spectroscopic information also to investigate the question of its parent population. Four spectra were acquired at the TNG in 2007-2008, when the source was in a relatively faint state. In three cases we were able to measure the broad Ha and several narrow emission lines. A comparison with previous results suggests that the broad Ha has increased by ~50% in ten years, a change not unusual for Broad Lined AGN. We estimated a black hole mass for BL Lac of 4-6 10^8 solar masses from its relation with the bulge luminosity. The virial mass estimated from the spectroscopic data is instead 20-30 times smaller. We suggest that this discrepancy is due to the BL Lac BLR being underluminous. Finally, we addressed the problem of the BL Lac parent population, comparing its isotropic quantities with those of other AGN classes. From the point of view of the narrow emission line spectrum, the source locates close to low-excitation radio galaxies. When also considering its diffuse radio power, an association with FRI radio galaxies is severely questioned due to the lower radio luminosity (at give line luminosity) of BL Lac. The narrow line and radio luminosities of BL Lac instead match those of a sample of miniature radio galaxies, which however do not show a BLR. Yet, if existing, "misaligned BL Lac" objects should have entered that sample. We also rule out the possibility that they have been excluded because of a QSO optical appearance. The observational constraints suggest that BL Lac is caught in a short term transient stage, which does not leave a detectable evolutionary "trace" in the AGN population. We speculate on a scenario that can account for the observed properties. [ABRIDGED]

Observations made during the last ten years with the Chandra X-ray Observatory have shed much light on the cooling gas in the centers of clusters of galaxies and the role of active galactic nucleus (AGN) heating. Cooling of the hot intracluster medium in cluster centers can feed the supermassive black holes found in the nuclei of the dominant cluster galaxies leading to AGN outbursts which can reheat the gas, suppressing cooling and large amounts of star formation. AGN heating can come in the form of shocks, buoyantly rising bubbles that have been inflated by radio lobes, and the dissipation of sound waves.

In recent years, ground-based very-high-energy (VHE; E>100 GeV) gamma-ray astronomy has experienced a major breakthrough with the impressive astrophysical results obtained mainly by the current generation experiments like H.E.S.S., MAGIC, MILAGRO and VERITAS. The ground-based Imaging Air Cherenkov Technique for detecting VHE gamma-rays has matured, and a fast assembly of inexpensive and robust telescopes is possible. The goal for the next generation of instruments is to increase their sensitivity by a factor >10 compared to current facilities, to extend the accessible gamma-ray energies from a few tens of GeV to a hundred TeV, and to improve on other parameters like the energy and angular resolution (improve the point-spread function by a factor 4-5 w.r.t. current instruments). The Cherenkov Telescope Array (CTA) project is an initiative to build the next generation ground-based gamma-ray instrument, will serve as an observatory to a wide astrophysics community. I discuss the key physics goals and resulting design considerations for CTA, the envisaged technical solutions chosen, and the organizational and operational requirements for operating such a large-scale facility as well as the specific needs of VHE gamma-ray astronomy.

The characteristic size of early-type galaxies (ETGs) of given stellar mass is observed to increase significantly with cosmic time, from redshift z>2 to the present. A popular explanation for this size evolution is that ETGs grow through dissipationless ("dry") mergers, thus becoming less compact. Combining N-body simulations with up-to-date scaling relations of local ETGs, we show that such an explanation is problematic, because dry mergers do not decrease the galaxy stellar-mass surface-density enough to explain the observed size evolution, and also introduce substantial scatter in the scaling relations. Based on our set of simulations, we estimate that major and minor dry mergers increase half-light radius and projected velocity dispersion with stellar mass (M) as M^(1.09+/-0.29) and M^(0.07+/-0.11), respectively. This implies that: 1) if the high-z ETGs are indeed as dense as estimated, they cannot evolve into present-day ETGs via dry mergers; 2) present-day ETGs cannot have assembled more than ~45% of their stellar mass via dry mergers. Alternatively, dry mergers could be reconciled with the observations if there was extreme fine tuning between merger history and galaxy properties, at variance with our assumptions. Full cosmological simulations will be needed to evaluate whether this fine-tuned solution is acceptable.

Recent high-resolution measurements suggest that the soft X-ray spectrum of obscured Radio Galaxies (RG) exhibits signatures of photoionised gas (e.g. 3C 445 and 3C 33) similar to those observed in radio-quiet obscured Active Galactic Nuclei (AGN). While signatures of warm absorbing gas covering a wide range of temperature and ionisation states have been detected in about one half of the population of nearby Seyfert 1 galaxies, no traces of warm absorber gas have been reported to date in the high-resolution spectra of Broad Line Radio Galaxies (BLRG). We present here the first detection of a soft X-ray warm absorber in the powerful FRII BLRG 3C 382 using the Reflection Grating Spectrometer (RGS) on-board XMM-Newton. The absorption gas appears to be highly ionised, with column density of the order of 10^{22} cm^{-2}, ionisation parameter log\xi>2 erg cm s^{-1} and outflow velocities of the order of 10^{3} km s^{-1}. The absorption lines may come from regions located outside the torus, however at distances less than 60 pc. This result may indicate that a plasma ejected at velocities near the speed of light and a photoionised gas with slower, outflow velocities can coexist in the same source beyond the Broad Line Regions.

The absolute luminosity of the Fe Kalpha emission line from matter illuminated by X-rays in astrophysical sources is nontrivial to calculate except when the line-emitting medium is optically-thin to absorption and scattering. We characterize the Fe Kalpha line flux using a dimensionless efficiency, defined as the fraction of continuum photons above the Fe K shell absorption edge threshold energy that appear in the line. The optically-thin approximation begins to break down even for column densities as small as 2 x 10^22 cm^-2. We show how to obtain reliable estimates of the Fe Kalpha line efficiency in the case of cold, neutral matter, even for the Compton-thick regime. We find that, regardless of geometry and covering factor, the largest Fe Kalpha line efficiency is attained well before the medium becomes Compton-thick. For cosmic elemental abundances it is difficult to achieve an efficiency higher than a few percent under the most favorable conditions and lines of sight. For a given geometry, Compton-thick lines-of-sight may have Fe Kalpha line efficiencies that are orders of magnitude less than the maximum possible for that geometry. Configurations that allow unobscured views of a Compton-thick reflecting surface are capable of yielding the highest efficiencies. Our results can be used to estimate the predicted flux of the narrow Fe Kalpha line at ~6.4 keV from absorption models in AGN. In particular we show that contrary to a recent claim in the literature, absorption dominated models for the relativistic Fe Kalpha emission line in MCG -6-30-15 do not over-predict the narrow Fe Kalpha line for any column density or covering factor.

We present optical to very-high energy (VHE) gamma-ray observations of Mrk 421 between 2008 May 24 and June 23. A high-energy (HE) gamma-ray signal was detected by AGILE-GRID during June 9-15, brighter than the average flux observed by EGRET in Mrk 421 by a factor of approx. 1.5. In 20-60 keV X-rays, a large-amplitude 5-day flare (June 9-15) was resolved with a maximum flux of approx. 55 mCrab. SuperAGILE, RXTE/ASM and Swift/BAT data show a clearly correlated flaring structure between soft and hard X-rays, with a high flux/amplitude variability in hard X-rays. Hints of the same flaring behavior is also detected in the simultaneously recorded GASP-WEBT optical data. A target of opportunity observation by Swift near the flare maximum on June 12-13 revealed the highest 2-10 keV flux ever observed (>100 mCrab) and a peak synchrotron energy of approx. 3 keV, a large shift from typical values of 0.5-1 keV. Observations at VHE (E>200 GeV) gamma-rays during June 6-8 show the source flux peaking in a bright state, well correlated with the simultaneous peak in the X-rays. The gamma-ray flare can be interpreted within the framework of the Synchrotron Self Compton model in terms of a rapid acceleration of leptons in the jet.

We investigate the thermodynamic and chemical structure of the intracluster medium (ICM) across a statistical sample of 20 galaxy clusters analysed with the Chandra X-ray satellite. In particular, we focus on the scaling properties of the gas density, metallicity and entropy and the comparison between clusters with and without cool cores (CCs). We find marked differences between the two categories except for the gas metallicity, which declines strongly with radius for all clusters (Z ~ r^{-0.31}), outside ~0.02 r500. The scaling of gas entropy is non-self-similar and we find clear evidence of bimodality in the distribution of logarithmic slopes of the entropy profiles. With only one exception, the steeper sloped entropy profiles are found in CC clusters whereas the flatter slope population are all non-CC clusters. We explore the role of thermal conduction in stabilizing the ICM and conclude that this mechanism alone is sufficient to balance cooling in non-CC clusters. However, CC clusters appear to form a distinct population in which heating from feedback is required in addition to conduction. Under the assumption that non-CC clusters are thermally stabilized by conduction alone, we find the distribution of Spitzer conduction suppression factors, f_c, to be log-normal, with a log (base 10) mean of -1.50+/-0.03 (i.e. f_c=0.032) and log standard deviation 0.39+/-0.02.

Glycolaldehyde is the simplest of the monosaccharide sugars and is directly linked to the origin of life. We report on the detection of glycolaldehyde (CH2OHCHO) towards the hot molecular core G31.41+0.31 through IRAM PdBI observations at 1.4, 2.1, and 2.9 mm. The CH2OHCHO emission comes from the hottest (> 300 K) and densest (>2E8 cm^-3) region closest (< 10^4 AU) to the (proto)stars. The comparison of data with gas-grain chemical models of hot cores suggests for G31.41+0.31 an age of a few 10^5 yr. We also show that only small amounts of CO need to be processed on grains in order for existing hot core gas-grain chemical models to reproduce the observed column densities of glycolaldehyde, making surface reactions the most feasible route to its formation.

We present the results of the simultaneous deep XMM and Chandra observations of the bright Seyfert 1.9 galaxy MCG-5-23-16, which is thought to have one of the best known examples of a relativistically broadened iron K-alpha line. The time averaged spectral analysis shows that the iron K-shell complex is best modeled with an unresolved narrow emission component (FWHM < 5000 km/s, EW ~ 60 eV) plus a broad component. This latter component has FWHM ~ 44000 km/s and EW ~ 50 eV. Its profile is well described by an emission line originating from an accretion disk viewed with an inclination angle ~ 40^\circ and with the emission arising from within a few tens of gravitational radii of the central black hole. The time-resolved spectral analysis of the XMM EPIC-pn spectrum shows that both the narrow and broad components of the Fe K emission line appear to be constant in time within the errors. We detected a narrow sporadic absorption line at 7.7 keV which appears to be variable on a time-scale of 20 ksec. If associated with Fe XXVI Ly-alpha this absorption is indicative of a possibly variable, high ionization, high velocity outflow. The variability of this absorption feature appears to rule out a local (z=0) origin. The analysis of the XMM RGS spectrum reveals that the soft X-ray emission of MCG-5-23-16 is likely dominated by several emission lines superimposed on an unabsorbed scattered power-law continuum. The lack of strong Fe L shell emission together with the detection of a strong forbidden line in the O VII triplet is consistent with a scenario where the soft X-ray emission lines are produced in a plasma photoionized by the nuclear emission.

We collected a sample of 661 confirmed and 361 possible BL Lac candidates from the recent catalog of BL Lac objects (Veron-Cetty & Veron 2006). We searched these sources in the recent data release DR5 of the Sloan Digital Sky Survey (SDSS) and found spectra were available for 169 and 109 confirmed and possible BL Lac candidates respectively. We found 32 candidates from confirmed and 19 candidates from possible BL Lac lists have non featureless spectra and are thus possibly not BL Lac candidates. We report here the preliminary results from our analysis of a sample of 278 BL Lac objects.

We present aperture synthesis imaging of dense molecular gas in the Large Magellanic Cloud, taken with the prototype millimeter receivers of the Australia Telescope Compact Array (ATCA). Our observations of the N113 HII region reveal a condensation with a size of ~6" (1.5 pc) FWHM, detected strongly in the 1-0 lines of HCO+, HCN and HNC, and weakly in C_2H. Comparison of the ATCA observations with single-dish maps from the Mopra Telescope and sensitive spectra from the Swedish-ESO Submillimetre Telescope indicates that the condensation is a massive clump of ~10^4 solar masses within a larger ~10^5 solar mass molecular cloud. The clump is centered adjacent to a compact, obscured HII region which is part of a linear structure of radio continuum sources extending across the molecular cloud. We suggest that the clump represents a possible site for triggered star formation. Examining the integrated line intensities as a function of interferometer baseline length, we find evidence for decreasing HCO+/HCN and HCN/HNC ratios on longer baselines. These trends are consistent with a significant component of the HCO+ emission arising in an extended clump envelope and a lower HCN/HNC abundance ratio in dense cores.

We report the XMM-Newton observation of a large X-ray flare from the Herbig Ae star V892 Tau. The apparent low mass companion of V892 Tau, V892 Tau NE, is unresolved by XMM-Newton. Nevertheless there is compelling evidence from combined XMM-Newton and Chandra data that the origin of the flare is the Herbig Ae star V892 Tau. During the flare the X-ray luminosity of V892 Tau increases by a factor of ~15, while the temperature of the plasma increases from kT ~ 1.5 keV to kT ~ 8 keV. From the scaling of the flare event, based on hydrodynamic modeling, we conclude that a 500 G magnetic field is needed in order to confine the plasma. Under the assumptions that a dynamo mechanism is required to generate such a confining magnetic field and that surface convection is a necessary ingredient for a dynamo, our findings provide indirect evidence for the existence of a significant convection zone in the stellar envelope of Herbig Ae stars.