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This paper aims to provide new insights on the origin of the TeV source VER J1907+062 through new high-quality radio observations. We used the Karl G. Jansky Very Large Array (VLA) to observe the whole extension of VER J1907+062 at 1.5 GHz with a mosaicking technique and the PSR J1907+0602 in a single pointing at 6 GHz. These data were used together with $^{12}$CO and atomic hydrogen observations obtained from public surveys to investigate the interstellar medium in the direction of VER J1907+062. The new radio observations do not show any evidence of a pulsar wind nebula (PWN) driven by the pulsars present in the field and no radio counterpart to the proposed X-ray PWN powered by PSR J1907+0602 is seen in the new VLA image at 6 GHz down to a noise level of 10 $\mu$Jy/beam. Molecular clouds were discovered over the eastern, southern, and western borders of the radio shell of G40.5$-$0.5, suggesting an association with this supernova remnant. We explored several scenarios for the origin of VER J1907+062. We propose as the most probable scenario one in which the TeV emission is produced by two separated gamma-ray sources located at different distances: one of leptonic origin and associated with a PWN powered by PSR J1907+0602 at $\sim 3.2$ kpc and another of hadronic origin and produced by the interaction between G40.5$-$0.5 and the surrounding molecular gas at $\sim 8.7$ kpc., Comment: Accepted for publicacion in MNRAS. Preprint version

We performed three-dimensional magnetohydrodynamic simulations to study the evolution of a supernova remnant (SNR) in a turbulent neutral atomic interstellar medium. The media used as background shares characteristics with the Solar neighbourhood and the SNR has mass and energy similar to those of a Type Ia object. Our initial conditions consist of dense clouds in a diluted medium, with the main difference between simulations being the average magnitude of the magnetic field. We measured amplifications of the magnetic energy of up to 34$\%$ and we generated synthetic maps that illustrate how the same object can show different apparent geometries and physical properties when observed through different lines of sight.

We present the results of XMM-Newton observations toward the pulsar PSR J1826$-$1256, which lies at 5$^{\prime}$.4 from the centroid of the TeV source HESS J1826$-$130. These data show an elongated nebula with the pulsar located in the northern border with the emission in the direction of the peak of the very high energy source. The spectral study of the X-ray emission shows a clear softening of the photon index with increasing distance from the pulsar. We discuss the connection among the pulsar, its nebula, and the HESS source.

Aims. The goal of this paper is to detect synchrotron emission from the relic electrons of the crushed pulsar wind nebula (PWN) HESS J1825-137 and to investigate the origin of the $\gamma$-ray emission from HESS J1826-130.\\ Methods. The study of HESS J1825-137 was carried out on the basis of new radio observations centred at the position of PSR J1826-1334 performed with the Karl G. Jansky Very Large Array at 1.4 GHz in configurations B and C. To investigate the nature of HESS J1826-130, we reprocessed unpublished archival data obtained with XMM-Newton.\\ Results. The new radio continuum image towards PSR J1826-1334 reveals a bright radio source, with the pulsar located in its centre, which suggests that this feature could be the radio counterpart of the compact component of the PWN detected at high energy. The new 1.4 GHz radio data do not reveal emission with an extension comparable with that observed in $\gamma$-rays for the HESS J1825-137 source. On the other hand, the XMM-Newton study of the region including PSR J1826-1256 reveals an elongated non-thermal X-ray emitting nebula with the pulsar located in the northern border and a tail towards the peak of the very high energy source. The spectrum is characterized by a power law with a photon index going from 1.6 around the pulsar to 2.7 in the borders of the nebula, a behaviour consistent with synchrotron cooling of electrons. From our X-ray analysis we propose that HESS J1826-130 is likely produced by the PWN powered by PSR J1826-1256 via the inverse Compton mechanism., Comment: 9 pages, 5 figures, 4 tables. Accepted for publication in the Astronomy & Astrophysics Journal. The quality of the images has been degraded

In the present work we have modeled the supernova remnant (SNR) G296.5+10, by means of 3D magnetohydrodynamics (MHD) simulations. This remnant belongs to the bilateral SNR group and has an additional striking feature: the rotation measure (RM) in its eastern and western parts are very different. In order to explain both the morphology observed in radio-continuum and the RM, we consider that the remnant expands into a medium shaped by the superposition of the magnetic field of the progenitor star with a constant Galactic magnetic field. We have also carried out a polarization study from our MHD results, obtaining synthetic maps of the linearly polarized intensity and the Stokes parameters. This study reveals that both the radio morphology and the reported RM for G$296.5+10$ can be explained if the quasi-parallel acceleration mechanism is taking place in the shock front of this remnant., Comment: 9 pages, 7 figures, accepted for publication in MNRAS

We study the molecular and the ionized gas in a possible precursor of an UC HII region to contribute to the understanding of how high-mass stars build-up their masses once they have reached the zero-age main secuence. We carried out molecular observations toward the position of the Red MSX source G052.9221-00.4892, using ASTE in the 12CO, 13CO, and C18O J=3-2, and HCO+ J=4-3 lines. We also present radio continuum observations at 6 GHz carried out with the JVLA interferometer. Combining these observations with public infrared data allowed us to inquire about the nature of the source. The analysis of the molecular observations reveals the presence of a kinetic temperature and H2 column density gradients across the molecular clump in which the source is embedded, with the hotter and less dense gas in the inner region. The 12CO J=3-2 emission shows evidence of misaligned massive molecular outflows, with the blue lobe in positional coincidence with a jet-like feature seen at 8 um. The radio continuum emission shows a slightly elongated compact radio source in positional coincidence with the Red MSX source. The polar-like morphology of this compact radio source perfectly matches the hourglass-like morphology exhibited by the source in the Ks-band. The axes of symmetry of the radio source and the near-IR nebula are perfectly aligned. Based on the multiwavelength analysis, we suggest that the analyzed source could be transiting a HC HII region phase, in which the young central star emits winds and ionizing radiation through the poles. By the other hand, according to a comparison between the Br-gamma and the radio flux density, the source would be in a more evolved evolutionary stage of an optically thin UC HII region in photoionization equilibrium. If this is the case, from the radio continuum emission, we can conjecture upon the spectral type of its exciting star which would be a B0.5V., Comment: Accepted in A&A. August 22, 2017

Using observations carried out with the GMRT, we performed high-quality full-synthesis imaging at 610 MHz of the source G29.37+0.1, which is an as-yet-unclassified object linked to the TeV source HESS J1844-030. These data, combined with observations at 1400 MHz from MAGPIS were used to investigate the properties of its radio emission. Additionally, we reprocessed XMM-Newton and Chandra archival data. G29.37+0.1 mainly consists of a bright twisted structure, named the S-shaped feature. The high sensitivity of the new GMRT observations allowed the identification of potential lobes, jets, and a nuclear central region in the S-shaped morphology of G29.37+0.1. We also highlight the detection of diffuse and low surface brightness emission enveloping the brightest emitting regions. The brightest emission in G29.37+0.1 has a radio synchrotron spectral index 0.59+/-0.09. Variations in the spectral behavior are observed across the whole radio source with the flattest spectral features in the central nuclear and jets components (alpha~0.3). These results lead us to conclude that the brightest radio emission from G29.37+0.1 likely represents a newly recognized radio galaxy. The identification of optical and infrared counterparts to the emission from the core of G29.37+0.1 strengthens our interpretation of an extragalactic origin of the radio emission. Our spectral analysis demonstrated that a non-thermal origin for the X-ray emission compatible with a pulsar wind nebula is quite possible. The analysis of the spatial distribution of the CO gas revealed the presence of a complex of molecular clouds located in projection adjacent to the radio halo emission and probably interacting with it. We propose that the faint halo represents a composite supernova remnant with a pulsar powered component given by the diffuse X-ray emission superimposed along the line of sight to the radio galaxy., Comment: 12 figures, accepted to be published in Astronomy and Astrophysics Main Journal

We introduce a distinct method to perform spatially-resolved spectral analysis of astronomical sources with highly structured X-ray emission. The method measures the surface brightness of neighbouring pixels to adaptively size and shape each region, thus the spectra from the bright and faint filamentary structures evident in the broadband images can be extracted. As a test case, we present the spectral analysis of the complete X-ray emitting plasma in the supernova remnant Puppis A observed with XMM-Newton and Chandra. Given the angular size of Puppis A, many pointings with different observational configurations have to be combined, presenting a challenge to any method of spatially-resolved spectroscopy. From the fit of a plane-parallel shocked plasma model we find that temperature, absorption column, ionization time scale, emission measure and elemental abundances of O, Ne, Mg, Si, S and Fe, are smoothly distributed in the remnant. Some regions with overabundances of O-Ne-Mg, previously characterized as ejecta material, were automatically selected by our method, proving the excellent response of the technique. This method is an advantageous tool for the exploitation of archival X-ray data., Comment: Accepted in Astronomy & Astrophysics

RCW 86 is a young supernova remnant (SNR) showing a shell-type structure at several wavelengths and is thought to be an efficient cosmic-ray (CR) accelerator. Earlier \textit{Fermi} Large Area Telescope results reported the detection of $\gamma$-ray emission coincident with the position of RCW 86 but its origin (leptonic or hadronic) remained unclear due to the poor statistics. Thanks to 6.5 years of data acquired by the \textit{Fermi}-LAT and the new event reconstruction Pass 8, we report the significant detection of spatially extended emission coming from RCW 86. The spectrum is described by a power-law function with a very hard photon index ($\Gamma = 1.42 \pm 0.1_{\rm stat} \pm 0.06_{\rm syst}$) in the 0.1--500 GeV range and an energy flux above 100 MeV of ($2.91$ $\pm$ $0.8_{\rm stat}$ $\pm$ $0.12_{\rm syst}$) $\times$ $10^{-11}$ erg cm$^{-2}$ s$^{-1}$. Gathering all the available multiwavelength (MWL) data, we perform a broadband modeling of the nonthermal emission of RCW 86 to constrain parameters of the nearby medium and bring new hints about the origin of the $\gamma$-ray emission. For the whole SNR, the modeling favors a leptonic scenario in the framework of a two-zone model with an average magnetic field of 10.2 $\pm$ 0.7 $\mu$G and a limit on the maximum energy injected into protons of 2 $\times$ 10$^{49}$ erg for a density of 1 cm$^{-3}$. In addition, parameter values are derived for the North-East (NE) and South-West (SW) regions of RCW 86, providing the first indication of a higher magnetic field in the SW region., Comment: 13 pages, 10 figures, accepted for publication in ApJ; Corresponding authors : Benjamin Condon, Marianne Lemoine-Goumard, Micaela Caragiulo

The main goal of this paper is to provide new insights on the origin of the observable flux of gamma rays from HESS J1809-193 using new high-quality observations in the radio domain. We used the Expanded Very Large Array (now known as the Karl G. Jansky Very large Array, JVLA) to produce a deep full-synthesis imaging at 1.4 GHz of the vicinity of PSR J1809-1917. These data were used in conjunction with 12CO observations from the James Clerk Maxwell Telescope in the transition line J=3-2 and atomic hydrogen data from the Southern Galactic Plane Survey to investigate the properties of the interstellar medium in the direction of the source HESS J1809-193. The new radio continuum image, obtained with a synthesized beam of 8"x4" and a sensitivity of 0.17 mJy/beam, reveals with unprecedented detail all the intensity structures in the field. No radio counterpart to the observed X-ray emission supposed to be a pulsar wind nebula powered by PSR J1809-1917 is seen in the new JVLA image. We discovered a system of molecular clouds on the edge of the supernova remnant (SNR) G11.0-0.0 shock front, which is positionally coincident with the brightest part of the TeV source HESS J1809-193. We determine, on the basis of kinematic and morphological evidences, a physical link of the SNR with the clouds for which we estimated a total (molecular plus atomic) mass of ~3 x10^3 Mo and a total proton density in the range 2-3 x 10^3 cm-3. We propose as the most likely origin of the very high-energy gamma-ray radiation from HESS J1809-193 a hadronic mechanism through collisions of ions accelerated at the SNR G11.0-0.0 shock with the molecular matter in the vicinity of the remnant., Comment: 7 pages, 5 figures, Accepted to be published in the Astronomy and Astrophysics Main Journal

HII regions are particularly interesting because they can generate dense layers of gas and dust, elongated columns or pillars of gas pointing towards the ionizing sources, and cometary globules of dense gas, where triggered star formation can occur. Understanding the interplay between the ionizing radiation and the dense surrounding gas is very important to explain the origin of these peculiar structures, and hence to characterize triggered star formation. G46.5-0.2 (G46), a poorly studied galactic HII region located at about 4 kpc, is an excellent target to perform this kind of studies. Using public molecular data extracted from the Galactic Ring Survey (13CO J=1-0) and from the James Clerk Maxwell Telescope data archive (12CO, 13CO, C18O J=3-2, HCO+ and HCN J=4-3), and infrared data from the GLIMPSE and MIPSGAL surveys, we perform a complete study of G46, its molecular environment and the young stellar objects placed around it. We found that G46, probably excited by an O7V star, is located close to the edge of the GRSMC G046.34-00.21 molecular cloud. It presents a horse-shoe morphology opening in direction of the cloud. We observed a filamentary structure in the molecular gas likely related to G46 and not considerable molecular emission towards its open border. We found that about 10' towards the southwest of G46 there are some pillar-like features, shining at 8 um and pointing towards the HII region open border. We propose that the pillar-like features were carved and sculpted by the ionizing flux from G46. We found several young stellar objects likely embedded in the molecular cloud grouped in two main concentrations: one, closer to the G46 open border consisting of Class II type sources, and other one mostly composed by Class I type YSOs located just ahead the pillars-like features, strongly suggesting an age gradient in the YSOs distribution., Comment: Accepted for publication in The Astronomical Journal (April 14, 2015). Some figures were degraded to reduce file size

HESS J1943+213 is a TeV source close to the Galactic plane proposed to be a BL Lac object. Our high resolution EVN observation failed to recover two thirds of the source flux density detected simultaneously by the WSRT. Our recent e-MERLIN observations in L and C bands show only a point source with flux density comparable to the EVN detection. Thus the structure responsible for the missing flux density has to be larger than 2". It may be related to the presumed extragalactic source (thus would have a kpc-scale size), or to the Galactic foreground material close to the line of sight to the source., Comment: 4 pages, 1 figure, appears in the proceedings of the 12th European VLBI Network Symposium and Users Meeting (7-10 October 2014, Cagliari, Italy), eds. A. Tarchi, M. Giroletti & L. Feretti. Proceedings of Science, PoS(EVN 2014)078

We present new high angular resolution and high sensitivity radio observations toward the neutron star RX J0007.0+7303, carried out with the Karl G. Jansky Very Large Array at 1.5 GHz. This source powers a pulsar wind nebula (PWN) only detected in the X-ray and gamma-ray domains. The new high quality radio observations do not show any evidence of a source, either point-like or extended, that could be interpreted as the radio counterpart of the high energy PWN, down to a noise level of 15 mJy/beam., Comment: Presented at the 33rd International Cosmic Ray Conference (ICRC), Rio de Janeiro, July 2013

To characterize a bright-rimmed cloud embedded in the HII region Sh2-48 searching for evidence of triggered star formation. We carried out observations towards a region of 2'x2' centered at RA=18h 22m 11.39s, dec.=-14deg 35m 24.81s (J2000) using the Atacama Submillimeter Telescope Experiment (ASTE; Chile) in the 12CO J=3-2,13CO J=3-2, HCO+ J=4-3, and CS J=7-6 lines with an angular resolution of about 22". We also present radio continuum observations at 5 GHz carried out with the Jansky Very Large Array (JVLA; EEUU) interferometer with a synthetized beam of 7"x5". The analysis of our molecular observations reveals the presence of a relatively dense clump with n(H_2)~3x10^3 cm^-3, located in projection onto the interior of the HII region Sh2-48. The emission distribution of the four observed molecular transitions has, at VLSR~38 kms^-1, morphological anti-correlation with the bright-rimmed cloud as seen in the optical emission. From the new radio continuum observations we identify a thin layer of ionized gas located at the border of the clump which is facing to the ionizing star. The ionized gas has an electron density of about 73 cm^-3 which supports the hypothesis that the clump is being photoionized by the nearby star, BD-14 5014. From the evaluation of the pressure balance between the ionized and molecular gas, we conclude that the clump would be in a pre-pressure balance state with the shocks being driven into the surface layer. Two YSO candidates (class I), are placed slightly beyond the bright rim suggesting that their formation could have been triggered via the radiation-driven implosion process., Comment: Accepted for publication in Astronomy and Astrophysics

With the purpose of producing the first detailed full view of Puppis A in X-rays, we carried out new XMM-Newton observations covering the missing regions in the southern half of the supernova remnant (SNR) and combined them with existing XMM-Newton and Chandra data. The new images were produced in the 0.3-0.7, 0.7-1.0 and 1.0-8.0 energy bands. We investigated the SNR morphology in detail, carried out a multi-wavelength analysis and estimated the flux density and luminosity of the whole SNR. The complex structure observed across the remnant confirms that Puppis A evolves in an inhomogeneous, probably knotty interstellar medium. The southwestern corner includes filaments that perfectly correlate with radio features suggested to be associated with shock/cloud interaction. In the northern half of Puppis A the comparison with Spitzer infrared images shows an excellent correspondence between X-rays and 24 and 70 microns emission features, while to the south there are some matched and other unmatched features. X-ray flux densities of 12.6 X 10^-9, 6.2 X 10^-9, and 2.8 X 10^-9 erg cm^-2 s^-1 were derived for the 0.3-0.7, 0.7-1.0 and 1.0-8.0 keV bands, respectively. At the assumed distance of 2.2 kpc, the total X-ray luminosity between 0.3 and 8.0 keV is 1.2 X 10^37 erg s^-1. We also collected and updated the broad-band data of Puppis A between radio and GeV gamma-ray range, producing its spectral energy distribution. To provide constraints to the high-energy emission models, we re-analyzed radio data, estimating the energy content in accelerated particles to be Umin=4.8 X 10^49 erg and the magnetic field strength B=26 muG., Comment: Article accepted to be published in the Astronomy and Astrophysics Main Journal

The eastern border of the SNR G18.8+0.3, close to an HII regions complex, is a very interesting region to study the molecular gas that it is probably in contact with the SNR shock front. We observed the aforementioned region using the Atacama Submillimeter Telescope Experiment (ASTE) in the 12CO J=3-2, 13CO J=3-2, HCO+ J=4-3, and CS J=7-6 lines with an angular resolution of 22". To complement these observations, we analyzed IR, submillimeter and radio continuum archival data. In this work, we clearly show that the radio continuum "protrusion" that was early thought to belong to the SNR is an HII regions complex deeply embedded in a molecular clump. The new molecular observations reveal that this dense clump, belonging to an extended molecular cloud that surrounds the SNR southeast border, is not physically in contact with SNR G18.8+0.3, suggesting that the SNR shock front have not yet reached it or maybe they are located at different distances. We found some young stellar objects embedded in the molecular clump, suggesting that their formation should be approximately coeval with the SN explosion., Comment: Accepted for publication in A&A (Sept. 7, 2012)

The luminous blue variable (LBV) stars are peculiar very massive stars. The study of these stellar objects and their surroundings is important for understanding the evolution of massive stars and its effects on the interstellar medium. We study the LBV star candidate G26.47+0.02. Using several large-scale surveys in different frequencies we performed a multiwavelength study of G26.47+0.02 and its surroundings. We found a molecular shell (seen in the 13CO J=1-0 line) that partially surrounds the mid-infrared nebula of G26.47+0.02, which suggests an interaction between the strong stellar winds and the molecular gas. From the HI absorption and the molecular gas study we conclude that G26.47+0.02 is located at a distance of ~4.8 kpc. The radio continuum analysis shows a both thermal and non-thermal emission toward this LBV candidate, pointing to wind-wind collision shocks from a binary system. This hypothesis is supported by a search of near-IR sources and the Chandra X-ray analysis. Additional multiwavelength and long-term observations are needed to detect some possible variable behavior, and if that is found, to confirm the binary nature of the system., Comment: accepted in A&A 01/05/2012

Aims: We study the molecular environment of the luminous blue variable star G24.73+0.69 to investigate the origin of the two infrared shells around this massive star and to determine its effects on the surrounding interstellar medium. Methods: We analyze the distribution of the molecular gas using the 13CO J=1-0 emission extracted from the Galactic Ring Survey. We use near- and mid-infrared data from 2MASS and GLIMPSE to identify the young stellar objects in the field. Results: We discover the molecular counterpart of the outer infrared shell around G24.73+0.69. The CO shell was probably blown by the stellar wind of the star mainly during its main sequence phase. We also find molecular gas that corresponds to the inner infrared shell, although its origin remains uncertain. We find seven young stellar objects upon the molecular material, whose birth might have been triggered by the stellar wind of the luminous blue variable star. We suggest that both G24.73+0.69 and the progenitor of the nearby supernova remnant G24.7+0.6 were formed from the same natal cloud and represent the most evolved members of a so far undetected cluster of other massive stars., Comment: 11 pages, 4 figures degraded to reduce file size. Accepted for publication in A&A

We report on a multifrequency radio study of the supernova remnant (SNR) G338.3-0.0, in positional coincidence with the TeV source HESS J1640-465. To carry out this research we observed the SNR G338.3-0.0 using the Giant Metrewave Radio Telescope (GMRT) at 235, 610, and 1280 MHz. We also reprocessed archival data from the Australia Telescope Compact Array (ATCA) at 1290 and 2300 MHz. Also we conducted a search for radio pulsations towards a central point-like source, using the GMRT antennas at 610 and 1280 MHz. The molecular material in the region of the SNR was investigated based on observations made with the NANTEN telescope in the 12^CO (J=1-0) emission line. The new radio observations revealed a remnant with a bilateral morphology, which at 235 MHz has the western wing completely attenuated because of absorption due to foreground ionized gas. The quality of the new images allows us to provide accurate estimates for the total radio flux density of the whole SNR at different radio frequencies. From the new and existing flux density estimates between 235 and 5000 MHz we derived for the whole remnant a spectral index alpha=-0.51 +/-0.06 with a local free-free continuum optical depth at 235 MHz tau_{235}=0.9+/-0.3. No radio pulsations were detected towards the only radio point-like source within the HESS error circle. We derived upper limits of 2.0 and 1.0 mJy at 610 and 1280 MHz, respectively, for the pulsed flux towards this source. No radio counterpart was found for the pulsar wind nebula discovered in X-rays. The inspection of the interstellar molecular gas towards G338.3-0.0 and surroundings revealed that there is not any associated dense cloud that might explain a hadronic origin for the TeV detection., Comment: 7 pages, 4 figures. Accepted for publication in A&A

HESS J1943+213, a TeV point source close to the Galactic plane recently discovered by the H.E.S.S. collaboration, was proposed to be an extreme BL Lacertae object, though a pulsar wind nebula (PWN) nature could not be completely discarded. To investigate its nature, we performed high-resolution radio observations with the European Very Long Baseline Interferometry Network (EVN) and reanalyzed archival continuum and H {\sc i} data. The EVN observations revealed a compact radio counterpart of the TeV source. The low brightness temperature and the resolved nature of the radio source are indications against the beamed BL Lacertae hypothesis. The radio/X-ray source appears immersed in a $\sim$ 1\arcmin elliptical feature suggesting a possible galactic origin (PWN nature) for the HESS source. We found that HESS\,J1943+213 is located in the interior of a $\sim1\degr$ diameter H {\sc i} feature, and explored the possibility of they being physically related., Comment: Significantly revised and extended. Accepted for publication in ApJ (ApJ, 762, 63). (4 figures.)

We present the results of a new study of the molecular gas associated with the "extended green object" (EGO) G35.03+0.35. This object, very likely a massive young stellar object, is embedded in a molecular cloud at the border of an HII region. The observations were performed with the Atacama Submillimeter Telescope Experiment (ASTE) in the 12CO and 13CO J=3-2, HCO+ J=4-3, and CS J=7-6 lines with an angular resolution about 22". From the 12CO J=3-2 line we discovered outflowing activity of the massive young stellar object. We obtained a total mass and kinetic energy for the outflows of 30 M_sun and 3000 M_sun (km/s)^2 (6 x 10^{46} ergs), respectively. We discovered a HCO+ and CS clump towards the EGO G35.03+0.35. The detection of these molecular species supports the presence of molecular outflows and a dense molecular envelope with temperatures and densities above 40 K and 6 x 10^{6} cm^{-3}, respectively. Using public near- and mid-IR, and sub-mm data we investigated the spectral energy distribution confirming that EGO G35.03+0.35 is a massive young stellar object at the earliest evolutionary stage (i.e. a class I young stellar object). By anlysing radio continuum archival data we found three radio sources towards the object, suggesting the presence of several young stellar objects in the region. Our radio continuum analysis is consistent with the presence of at least one ultracompact HII region and an hypercompact HII region or a constant-velocity ionized wind source., Comment: Accepted (September 21, 2011) to be published in MNRAS

HESS J1858+020 is a weak gamma-ray source lying near the southern border of the SNR G35.6-0.4. A molecular cloud, composed by two clumps, shows signs of interaction with the SNR and with a nearby extended HII region. In particular, the southernmost clump coincides with the center of the HESS source. In this work we study this clump in detail with the aim of adding information that helps in the identification of the nature of the very-high energy emission. We observed the mentioned molecular clump using the Atacama Submillimeter Telescope Experiment (ASTE) in the 12CO J=3-2, 13CO J=3-2, HCO+ J=4-3 and CS J=7-6 lines with an angular resolution of 22". To complement this observations we analyzed IR and submillimeter continuum archival data. From the 12CO and 13CO J=3-2 lines and the 1.1 mm continuum emission we derived a density of between 10^{3} and 10^{4} cm^-3 for the clump. We discovered a young stellar object (YSO), probably a high mass protostar, embedded in the molecular clump. However, we did not observe any evidence of molecular outflows from this YSO which would reveal the presence of a thermal jet capable of generating the observed gamma-rays. We conclude that the most probable origin for the TeV gamma-ray emission are the hadronic interactions between the molecular gas and the cosmic rays accelerated by the shock front of the SNR G35.6-0.4., Comment: 11 pages, 5 figures. Accepted for publication in A&A (March 25, 2011)

The gamma-ray pulsar PSR B1706-44 and the adjacent supernova remnant (SNR) candidate G343.1-2.3 were observed by H.E.S.S. during a dedicated observation campaign in 2007. As a result of this observation campaign, a new source of very-high-energy (VHE; E > 100 GeV) gamma-ray emission, HESS J1708-443, was detected with a statistical significance of 7 sigma, although no significant point-like emission was detected at the position of the energetic pulsar itself. In this paper, the morphological and spectral analyses of the newly-discovered TeV source are presented. The centroid of HESS J1708-443 is considerably offset from the pulsar and located near the apparent center of the SNR, at RA(J2000) = 17h08m11s +/- 17s and Dec(J2000) = -44d20' +/- 4'. The source is found to be significantly more extended than the H.E.S.S. point spread function (~0.1 deg), with an intrinsic Gaussian width of 0.29 deg +/- 0.04 deg. Its integral flux between 1 and 10 TeV is ~ 3.8 x 10^-12 ph cm^-2 s^-1, equivalent to 17% of the Crab Nebula flux in the same energy range. The measured energy spectrum is well-fit by a power law with a relatively hard photon index Gamma = 2.0 +/- 0.1 (stat) +/- 0.2 (sys). Additional multi-wavelength data, including 330 MHz VLA observations, were used to investigate the VHE gamma-ray source's possible associations with the pulsar wind nebula of PSR B1706-44 and/or with the complex radio structure of the partial shell-type SNR G343.1-2.3., Comment: 15 pages, 6 figures, 3 tables; Accepted for publication in A&A; v2 paper remains the same, but all authors are now explicitly listed in arXiv entry

Identification of gamma-ray-emitting Galactic sources is a long-standing problem in astrophysics. One such source, 1AGL J2022+4032, coincident with the interior of the radio shell of the supernova remnant Gamma Cygni (SNR G78.2+2.1) in the Cygnus Region, has recently been identified by Fermi as a gamma-ray pulsar, LAT PSR J2021+4026. We present long-term observations of 1AGL J2022+4032 with the AGILE gamma-ray telescope, measuring its flux and light curve. We compare the light curve of 1AGL J2022+4032 with that of 1AGL J2021+3652 (PSR J2021+3651), showing that the flux variability of 1AGL J2022+4032 appears to be greater than the level predicted from statistical and systematic effects and producing detailed simulations to estimate the probability of the apparent observed variability. We evaluate the possibility that the gamma-ray emission may be due to the superposition of two or more point sources, some of which may be variable, considering a number of possible counterparts. We consider the possibility of a nearby X-ray quiet microquasar contributing to the flux of 1AGL J2022+4032 to be more likely than the hypotheses of a background blazar or intrinsic gamma-ray variabilty of LAT PSR J2021+4026., Comment: 7 pages, 7 figures, accepted for publication in Astronomy & Astrophysics

AIMS: We investigate the environment of the infrared dust bubble N65 and search for evidence of triggered star formation in its surroundings. METHODS: We performed a multiwavelength study of the region around N65 with data taken from large-scale surveys: Two Micron All Sky Survey, GLIMPSE, MIPSGAL, SCUBA, and GRS. We analyzed the distribution of the molecular gas and dust in the environment of N65 and performed infrared photometry and spectral analysis of point sources to search for young stellar objects and identify the ionizing star candidates. RESULTS: We found a molecular cloud that appears to be fragmented into smaller clumps along the N65 PDR. This indicates that the so-called collect and collapse process may be occurring. Several young stellar objects are distributed among the molecular clumps. They may represent a second generation of stars whose formation was triggered by the bubble expanding into the molecular gas. We dentified O-type stars inside N65, which are the most reliable ionizing star candidates., Comment: 15 pages, 10 figures, accepted for publication in A&A. Figures degraded to reduce file size

HESS J1858+020 is a weak gamma-ray source that does not have any clear cataloged counterpart at any wavelengths. Recently, the source G35.6-0.4 was re-identified as a SNR. The HESS source lies towards the southern border of this remnant. The purpose of this work is to investigate the interstellar medium around the mentioned sources in order to look for possible counterparts of the very-high energy emission. Using the 13CO J=1-0 line from the Galactic Ring Survey and mid-IR data from GLIMPSE we analyze the environs of HESS J1858+020 and SNR G35.6-0.4. The 13CO data show the presence of a molecular cloud towards the southern border of SNR G35.6-0.4 and at the same distance as the remnant. This cloud is composed by two molecular clumps, one, over the SNR shell and the other located at the center of HESS J1858+020. We estimate a molecular mass and a density of ~ 5 X 10^{3} Msun and ~ 500 cm^{-3}, respectively for each clump. Considering the gamma-ray flux observed towards HESS J1858+020, we estimate that a molecular cloud with a density of at least 150 cm^{-3} could explain the very-high energy emission hadronically. Thus, we suggest that the gamma-ray emission detected in HESS J1858+020 is due to hadronic mechanism. Additionally, analyzing mid-IR emission, we find that the region is active in star formation, which could be considered as an alternative or complementary possibility to explain the very-high energy emission., Comment: 6 pages, 3 figures, accepted for publication in A&A Letter

We investigate two multi-shell galactic supernova remnants (SNRs), Kes79 and G352.7-0.1, to understand the causes of such morphology. The research was carried out based on new and reprocessed archival VLA observations and XMM-Newton archival data. The surrounding was investigated based on data extracted from the HI Canadian Galactic Plane Survey, the 13^CO Galactic Ring Survey and the HI Southern Galactic Plane Survey. The present study revealed that the overall morphology of both SNRs is the result of the mass-loss history of their respective progenitor stars. Kes79 would be the product of the gravitational collapse of a massive O9 star evolving near a molecular cloud and within the precursor's wind-driven bubble, while G352.7-0.1 would be the result of interactions of the SNR with an asymmetric wind from the progenitor together with projection effects. No radio point source or pulsar wind nebula was found associated with the X-ray pulsar CXOU J185238.6+004020 in Kes79. The X-ray study of G352.7-0.1, on its hand, revealed that most of the thermal X-ray radiation completely fills in the interior of the remnant and originates in heated ejecta. Characteristic parameters, like radio flux, radio spectral index, age, distance, shock velocity, initial energy and luminosity, were estimated for both SNRs., Comment: 14 pages, 13 figures. Accepted to be published in Astronomy and Astrophysics

The supernova remnant (SNR) RX J1713.7-3946 (also known as G347.3-0.5) is part of the class of remnants dominated by synchrotron emission in X-rays. It is also one of the few shell-type SNRs observed at TeV energies allowing to investigate particle acceleration at SNRs shock. Our goal is to compare spatial and spectral properties of the remnant in X- and gamma-rays to understand the nature of the TeV emission. This requires to study the remnant at the same spatial scale at both energies. To complement the non-thermal spectrum of the remnant, we attempt to provide a reliable estimate for the radio flux density. In radio, we revisited ATCA data and used HI and mid-infrared observations to disentangle the thermal from the non-thermal emission. In X-rays, we produced a new mosaic of the remnant and degraded the spatial resolution of the X-ray data to the resolution of the HESS instrument to perform spatially resolved spectroscopy at the same spatial scale in X- and gamma-rays. Radial profiles were obtained to investigate the extension of the emission at both energies. We found that part of the radio emission within the SNR contours is thermal in nature. Taking this into account, we provide new lower and upper limits for the integrated synchrotron flux of the remnant at 1.4 GHz of 22 Jy and 26 Jy respectively. In X-rays, we obtained the first full coverage of RX J1713.7-3946 with XMM-Newton. The spatial variation of the photon index seen at small scale in X-rays is smeared out at HESS resolution. A non-linear correlation between the X- and gamma-ray fluxes of the type Fx \propto Fg^2.41 is found., Comment: 13 pages, 10 figures, accepted for publication in A&A. An image of the remnant with higher definition will be distributed through the XMM-Newton image gallery (http://xmm.esac.esa.int/external/xmm_science/gallery/public/)

The nature of the extended hard X-ray source XMMU J061804.3+222732 and its surroundings is investigated using XMM-Newton, Chandra, and Spitzer observations. This source is located in an interaction region of the IC 443 supernova remnant with a neighboring molecular cloud. The X-ray emission consists of a number of bright clumps embedded in an extended structured non-thermal X-ray nebula larger than 30" in size. Some clumps show evidence for line emission at ~1.9 keV and ~3.7 keV at the 99% confidence level. Large-scale diffuse radio emission of IC 443 passes over the source region, with an enhancement near the source. An IR source of about 14" x 7" size is prominent in the 24 um, 70 um, and 2.2 um bands, adjacent to a putative Si K-shell X-ray line emission region. The observed IR/X-ray morphology and spectra are consistent with those expected for J/C-type shocks of different velocities driven by fragmented supernova ejecta colliding with the dense medium of a molecular cloud. The IR emission of the source detected by Spitzer can be attributed to both continuum emission from an HII region created by the ejecta fragment and line emission excited by shocks. This source region in IC 443 may be an example of a rather numerous population of hard X-ray/IR sources created by supernova explosions in the dense environment of star-forming regions. Alternative Galactic and extragalactic interpretations of the observed source are also discussed., Comment: The Astrophysical Journal, v. 677 (April 2008), in press

We found a very likely counterpart to the recently discovered hard X-ray source IGR J2018+4043 in the multi-wavelength observations of the source field. The source, originally discovered in the 20-40 keV band, is now confidently detected also in the 40-80 keV band, with a flux of (1.4 +/- 0.4) x 10(-11) erg cm(-2) s(-1). A 5 ks Swift observation of the IGR J2018+4043 field revealed a hard point-like source with the observed 0.5-10 keV flux of 3.4(+0.7)(-0.8) x 10(-12) erg cm(-2) s(-1) (90% confidence level) at alpha = 20h18m38.55s, delta = +40d41m00.4s (with a 4.2" uncertainty). The combined Swift-INTEGRAL spectrum can be described by an absorbed power-law model with photon index gamma = 1.3 +/- 0.2 and N_H = 6.1(+3.2)(-2.2) x 10(22) cm(-2). In archival optical and infrared data we found a slightly extended and highly absorbed object at the Swift source position. There is also an extended VLA 1.4 GHz source peaked at a beam-width distance from the optical and X-ray positions. The observed morphology and multiwavelength spectra of IGR J2018+4043 are consistent with those expected for an obscured accreting object, i.e. an AGN or a Galactic X-ray binary. The identification suggests possible connection of IGR J2018+4043 to the bright gamma-ray source GEV J2020+4023 (3EG J2020+4017) detected by COS B and CGRO EGRET in the gamma-Cygni SNR field., Comment: 5 pages, 3 figures, uses emulateapj style

Aim: We observed the center of the supernova remnant Vela Jr in radio continuum in order to search for a counterpart to the compact central X-ray source CXOU J085201.4-461753, possibly a neutron star candidate which could be the remnant of the supernova explosion. Method: Observations were made with the Australia Telescope Compact Array at 13 and 20 cm. Spectral indices were obtained using flux density correlations of the data which were spatially filtered to have the same u-v coverage. A multiwavelength search for counterparts to the compact central X-ray source was made. Results: We compiled a new catalogue of 31 small diameter radio sources, including the previously known source PMN J0853-4620, listing the integrated flux densities at 20 cm and, for half of the sources, the flux densities at 13 cm with the corresponding spectral indices. All sources are unresolved at the present angular resolution except for Source 18, which is clearly elongated and lies strikingly close to CXOU J085201.4-461753. Our observations show no evidence for the existence of a pulsar wind driven nebula associated with the point X-ray source. Furthermore, Source 18 has a thermal spectrum with index +0.8 +/- 0.4, and appears to be the counterpart of the optical source Wray 16-30. In spite of the absence of OIII emission lines as reported in the literature, we find that this object could be explained as a low emission planetary nebula belonging to the ``butterfly'' morphological class. Conclusions: We conclude that if the radio source 18 is actually a planetary nebula, then CXOU J085201.4-461753 is more likely to be related to it rather than to Vela Jr., Comment: 9 pages, 4 figures, to appear in Astronomy and Astrophysics

We report on new VLA radio and XMM-Newton X-ray observations of the SNR G352.7-0.1. These high sensitivity, high resolution data reveal that G352.7-0.1 belongs to the thermal composite morphological class. Small scale structures in radio and X-ray emission are not always correlated and are different for the different X-rays bands examined. The distance to G352.7-0.1 can be constrained between 6.6 and 8.4 kpc. The study of the HI suggests that G352.7-0.1 is located within a cavity probably created by the stellar wind of the precursor star., Comment: 2 pages, 2 figures. To appear in the proceedings of "The X-Ray Universe 2005" conference, 2005 Sept 26-30, El Escorial, Madrid, Spain

We report INTEGRAL/IBIS gamma-ray and VLA radio observations of G0.570-0.018, a diffuse X-ray source recently discovered by ASCA and Chandra in the Galactic center region. Based on its spectrum and morphology, G0.570-0.018 has been proposed to be a very young supernova remnant. In this scenario, the presence of gamma-ray lines coming from the short-lived radioactive nucleus 44Ti as well as synchrotron radio continuum emission are expected. The first could provide informations on nucleosynthesis environments in the interior of exploding stars, the latter could probe the interaction between the supernova blast wave and the circumstellar/interstellar matter. We have not detected 44Ti lines nor any conspicuous radio feature associated with this source down to the achieved sensitivities. From the derived upper limits we set constraints on the nature of G0.570-0.018., Comment: 17 pages, 4 figures, accepted for publication in ApJ

We present a high-resolution (24 arcsec) study of the HI interstellar gas distribution around the radio-quiet neutron star Geminga. Based on Very Large Array (VLA) and MPIfR Effelsberg telescope data, we analyzed a 40' x 40' field around Geminga. These observations have revealed the presence of a neutral gas shell, 0.4 pc in radius, with an associated HI mass of 0.8 Msun, which surrounds Geminga at a radial velocity compatible with the kinematical distance of the neutron star. In addition, morphological agreement is observed between the internal face of the HI shell and the brightest structure of Geminga's tail observed in X-rays.We explore the possibility that this morphological agreement is the result of a physical association., Comment: One tarfile including a Latex file (7 pages) and two figures. Paper accepted for publication in Advances in Space Research; typos corrected; changes in section Results and Discussion after referee's suggestions. S. Johnston's affilation corrected

We present new results coming from the observations of the supernova remnant (SNR) RX J1713.7--3946 (also G347.3--0.5) performed in five distinct pointings with the EPIC instrument on board the satellite XMM-Newton. RX J1713.7--3946 is a shell-type SNR dominated by synchrotron radiation in the X-rays. Its emission (emission measure and photon index) as well as the absorption along the line-of-sight has been characterized over the entire SNR. The X-ray mapping of the absorbing column density has revealed strong well constrained variations (0.4 10^22 cm^-2 < NH < 1.1 10^22 cm^-2) and, particularly, a strong absorption in the southwest. Moreover, there are several clues indicating that the shock front of RX J1713.7--3946 is impacting the clouds responsible for the absorption as revealed for instance by the positive correlation between X-ray absorption and X-ray brightness along the western rims. The CO and HI observations show that the inferred cumulative absorbing column densities are in excellent agreement with the X-ray findings in different places of the remnant on condition that the SNR lies at a distance of 1.3 +/- 0.4 kpc, probably in the Sagittarius galactic arm, instead of the commonly accepted value of 6 kpc. An excess in the CO emission is found in the southwest suggesting that the absorption is due to molecular clouds. A search for OH masers in the southwestern region has been unsuccessful, possibly due to the low density of the clouds. The X-ray mapping of the photon index has also revealed strong variations (1.8 < Gamma < 2.6). [See the article for the entire abstract], Comment: 19 pages, 24 figures, accepted for publication in A&A

We have carried out an HI survey towards X-ray central compact objects (CCOs) inside supernova remnants (SNRs) which shows that many of them are placed within local HI minima. The nature of these minima is not clear, but the most likely explanation is that the CCOs have evacuated the neighboring gas. This survey also allowed us to detect a weak, diffuse radio nebula inside the SNR Vela Jr, probably created by the winds of its associated CCO., Comment: 2 pages, to appear in "Young Neutron Stars and Their Environments" (IAU Symposium 218, ASP Conference Proceedings), eds F. Camilo and B. M. Gaensler

We have carried out a study of the neutral hydrogen in the direction of the X-ray source 1E 161348-5055, a compact central object (CCO) located in the interior of the supernova remnant (SNR) RCW 103. The HI 21 cm line observations were carried out using the Australia Telescope Compact Array, complemented with single dish data from the Parkes radio telescope to recover information at all spatial scales. We derive a distance to RCW 103 of 3.3 kpc, in agreement with previous distance measurements. We have also detected a small hole in the HI emission which is positionally and kinematically coincident with the location of the CCO which confirms the association between the SNR and the CCO. This is the third case of a depression in HI emission seemingly associated with CCOs in SNRs. The characteristic parameters of the holes such as their size, eccentricity and evacuated mass are similar in all three cases. We estimate the absorbing HI column density towards 1E 161348-5055 to be ~6 x 10^{21} cm^{-2}, a value compatible with a blackbody solution for the CCO X-ray emission. However, the implied brightness temperature is very high comparedto most neutron stars. Moreover, the strong long-term variability in X-rays favours the hypothesis that 1E 161348-5055 is an accreting binary sourcerather than an isolated, cooling neutron star. An analysis of the continuum image obtained at 1.4 GHz from these observations shows no trace of a pulsar wind nebula around 1E 161348-5055, in spite of it being a young object., Comment: 12 pages, 4 gif figures, to appear in Publications of the Astronomical Society of Australia (PASA). Full postscript version with all 4 figures is available at http://www.physics.usyd.edu.au/~simonj/rcw103.ps.gz

We have observed the HI distribution in an area 40' x 40' around the neutron star candidate RX J0822-4300, which is located in the supernova remnant Puppis A. The observations of the 21 cm line were obtained with the Australia Telescope Compact Array (ATCA) and were combined with single dish data from the Southern Galactic Plane Survey. The spatial resolution is 90", and the velocity resolution, 1 km/s . A sensitivity of ~ 0.7 K was achieved. The results revealed a double lobed feature of reduced emission at +16 km/s, centered on the central compact object (CCO), and aligned with an HI hole blueshifted by 13 km/s. The HI depressions have probably been created by the sweeping up of ~ 2 solar masses. The alignement between the lobes and the optical expansion centre of Puppis A suggests that the CCO could be ejecting two opposite jets. The velocity at which the two lobes are best defined allowed us to confirm that the distance to Puppis A is 2.2 kpc, based on a systemic velocity of +16 km/s. The hydrogen column density computed using this systemic velocity is consistent with estimates from models for X-ray spectra, thus reinforcing our conclusion that the kinematic distance is 2.2 k pc., Comment: 8 pages, 2 ps/eps figures, plus 1 gif figure and 4 jpg figures, MNRAS, in press. Full postscript version with all 7 figures is available at http://www.physics.usyd.edu.au/~simonj/puppis.ps.gz

We report on Australia Telescope Compact Array (ATCA) HI observations carried out in the direction of bilateral supernova remnants (SNRs) with associated neutron stars: G296.5+10.0 and G320.4--1.2, in a search for the origin of such morphology. From these studies we conclude that in the case of G296.5+10.0, located far from the Galactic plane, the HI distribution has not influenced the present morphology of the SNR. In the case of G320.4--1.2, evolving in a denser medium, the combined action of the central pulsar, PSR B1509-58, with the peculiar distribution of the surrounding medium, has determined the observed characteristics of the SNR., Comment: to appear in "Neutron Stars in Supernova Remnants" (ASP Conference Proceedings), eds. P.O. Slane and B.M. Gaensler

Using the Australia Telescope Compact Array, we have carried out a survey of the HI emission in the direction of the ``barrel-shaped'' supernova remnant (SNR) G320.4-1.2 (MSH 15-52) and its associated young pulsar B1509-58. The angular resolution of the data is 4.0x2.7 arcmin, and the rms noise of the order of 30 mJy/beam (~0.5 K). The HI observations indicate that the N-NW radio limb has encountered a dense HI filament (density ~12 cm^-3) at the same LSR velocity than that of the SNR (V_LSR ~ -68 km/s). This HI concentration would be responsible for the flattened shape of the NW lobe of G320.4-1.2, and for the formation of the radio/optical/X-ray nebula RCW 89. The emission associated with the bright knots in the interior of RCW 89 can be explained as arising from the interaction between the collimated relativistic outflow from the pulsar and the denser part of this HI filament (density ~15 cm^-3). The S-SE half of the SNR, on the other hand, seems to have rapidly expanded across a lower density enviroment (density ~0.4 cm^-3). The HI data also reveal an unusual HI feature aligned with a collimated outflow generated by the pulsar, suggestive of association with the SNR. The anomalous kinematical velocity of this feature (V_LSR ~ 15 km/s), however, is difficult to explain., Comment: 7 pages, including 3 embedded PS figures + 4 separate JPEG images. Uses emulateapj.sty. Accepted to AJ

We present high resolution VLA images taken at the wavelengths of lambda 20 cm, lambda 6 cm, and lambda 3.6 cm in the vicinity of the pulsars PSR B1706-44 (PSR J1709-4428) and PSR B1643-43 (PSR J1646-4346). Both of these pulsars are young (<30,000 yrs) and have large spin-down luminosities (e+35 erg/sec) and hence are good candidates to search for extended synchrotron nebula excited by the relativistic pulsar wind. For PSR B1643-43 we found evidences of a 4'comet-shaped nebula, suggestive of a synchrotron ``wake'' left by a fast moving pulsar. PSR B1706-44 appears surrounded by a spherical nebula approximately 3 ' in diameter. Based on their morphology, the detection of significant linear polarization (>20%), and their flat radio spectra (alpha=0.25-0.3, where S_nu aprox nu^-alpha) we argue that these are wind nebulae powered by the rotational energy loss of the respective pulsars.

We present radio observations of a region in the vicinity of the young pulsar PSR B1853+01 in the supernova remnant W44. The pulsar is located at the apex of an extended feature with cometary morphology. We argue on the basis of its morphology and its spectral index and polarization properties that this is a synchrotron nebula produced by the spin down energy of the pulsar. The geometry and physical parameters of this pulsar-powered nebula and W44 are used to derive three different measures of the pulsar's transverse velocity. A range of estimates between 315 and 470 km/s are derived, resulting in a typical value of 375 km/s. The observed synchrotron spectrum from radio to X-ray wavelengths is used to put constraints on the energetics of the nebula and to derive the parameters of the pulsar wind., Comment: ApJ Let (in press)