@article {233, title = {{Excitation Mechanisms for HCN (1-0) and HCO+ (1-0) in Galaxies from the Great Observatories All-sky LIRG Survey}}, journal = {ArXiv e-prints}, year = {2015}, keywords = {Astrophysics - Astrophysics of Galaxies}, url = {http://adsabs.harvard.edu/abs/2015arXiv150907512P}, author = {Privon, G.~C. and Herrero-Illana, R. and Evans, A.~S. and Iwasawa, K. and Perez-Torres, M.~A. and Armus, L. and Diaz-Santos, T. and Murphy, E.~J. and Stierwalt, S. and Aalto, S. and Mazzarella, J.~M. and Barcos-Munoz, L. and Borish, H.~J. and Inami, H. and Kim, D.-C. and Treister, E. and Surace, J.~A. and Lord, S. and Conway, J. and Frayer, D.~T. and Alberdi, A.} } @book {181, title = {{The Spanish Square Kilometre Array White Book}}, series = {ArXiv e-prints}, year = {2015}, keywords = {Astrophysics - Instrumentation and Methods for Astrophysics}, url = {http://adsabs.harvard.edu/abs/2015arXiv150603474A}, author = {Acosta-Pulido, J.~A. and Agudo, I. and Alberdi, A. and Alcolea, J. and Alfaro, E.~J. and Alonso-Herrero, A. and Anglada, G. and Arnalte-Mur, P. and Ascasibar, Y. and Ascaso, B. and Azulay, R. and Bachiller, R. and Baez-Rubio, A. and Battaner, E. and Blasco, J. and Brook, C.~B. and Bujarrabal, V. and Busquet, G. and Caballero-Garcia, M.~D. and Carrasco-Gonzalez, C. and Casares, J. and Castro-Tirado, A.~J. and Colina, L. and Colomer, F. and de Gregorio-Monsalvo, I. and del Olmo, A. and Desmurs, J.-F. and Diego, J.~M. and Dominguez-Tenreiro, R. and Estalella, R. and Fernandez-Soto, A. and Florido, E. and Font, J. and Font, J.~A. and Fuente, A. and Garc{\'\i}a-Benito, R. and Garcia-Burillo, S. and Garc{\'\i}a-Lorenzo, B. and Gil de Paz, A. and Girart, J.~M. and Goicoechea, J.~R. and G{\'o}mez, J.~F. and Gonzalez-Garcia, M. and Gonz{\'a}lez-Mart{\'\i}n, O. and Gonzalez-Serrano, J.~I. and Gorgas, J. and Gorosabel, J. and Guijarro, A. and Guirado, J.~C. and Hern{\'a}ndez-Garc{\'\i}a, L. and Hernandez-Monteagudo, C. and Herranz, D. and R. Herrero-Illana and Hu, Y.-D. and Huelamo, N. and Huertas-Company, M. and Iglesias-Paramo, J. and Jeong, S. and Jimenez-Serra, I. and Knapen, J.~H. and Lineros, R.~A. and Lisenfeld, U. and Marcaide, J.~M. and Marquez, I. and Marti, J. and Marti, J.~M. and Mart{\'\i}-Vidal, I. and Martinez-Gonzalez, E. and Martin-Pintado, J. and Masegosa, J. and Mayen-Gijon, J.~M. and Mezcua, M. and Migliari, S. and Mimica, P. and Mold{\'o}n, J. and Morata, O. and Negueruela, I. and Oates, S.~R. and Osorio, M. and Palau, A. and Paredes, J.~M. and Perea, J. and P{\'e}rez-Gonz{\'a}lez, P.~G. and Perez-Montero, E. and M. A. P{\'e}rez-Torres and Perucho, M. and Planelles, S. and Pons, J.~A. and Prieto, A. and Quilis, V. and Ramirez-Moreta, P. and Ramos Almeida, C. and Rea, N. and Rib{\'o}, M. and Rioja, M.~J. and Rodriguez Espinosa, J.~M. and Ros, E. and Rubi{\~n}o-Martin, J.~A. and Ruiz-Granados, B. and Sabater, J. and Sanchez, S. and Sanchez-Contreras, C. and Sanchez-Monge, A. and Sanchez-Ramirez, R. and Sintes, A.~M. and Solanes, J.~M. and Sopuerta, C.~F. and Tafalla, M. and Tello, J.~C. and Tercero, B. and Toribio, M.~C. and Torrelles, J.~M. and Torres, M.~A.~P. and Usero, A. and Verdes-Montenegro, L. and Vidal-Garcia, A. and Vielva, P. and Vilchez, J. and Zhang, B.-B.} } @article {232, title = {{Sub-arcsec mid-IR observations of NGC 1614: Nuclear star-formation or an intrinsically X-ray weak AGN?}}, journal = {ArXiv e-prints}, year = {2015}, keywords = {Astrophysics - Astrophysics of Galaxies}, url = {http://adsabs.harvard.edu/abs/2015arXiv150907765P}, author = {Pereira-Santaella, M. and Colina, L. and Alonso-Herrero, A. and Usero, A. and Diaz-Santos, T. and Garcia-Burillo, S. and Alberdi, A. and Gonz{\'a}lez-Mart{\'\i}n, O. and Herrero-Illana, R. and Imanishi, M. and Levenson, N.~A. and Perez-Torres, M.~A. and Ramos Almeida, C.} } @article {2014ApJ...792...38P, title = {{Constraints on the Progenitor System and the Environs of SN 2014J from Deep Radio Observations}}, journal = {The Astrophysical Journal}, volume = {792}, year = {2014}, pages = {38}, abstract = {We report deep EVN and eMERLIN observations of the Type Ia SN 2014J in the nearby galaxy M82. Our observations represent, together with JVLA observations of SNe 2011fe and 2014J, the most sensitive radio studies of Type Ia SNe ever. By combining data and a proper modeling of the radio emission, we constrain the mass-loss rate from the progenitor system of SN 2014J to $\backslash$dot$\{$M$\}$ $\backslash$lesssim 7.0$\backslash$times 10\^{}$\{$-10$\}$ $\{$$\backslash$,$\{$M\_$\{$$\backslash$odot $\}$ $\backslash$,yr\^{}$\{$-1$\}$$\}$$\}$ (for a wind speed of 100 km s$^{-1}$). If the medium around the supernova is uniform, then n $_{ISM}$ {\l}t}\~{} 1.3 cm$^{-3}$, which is the most stringent limit for the (uniform) density around a Type Ia SN. Our deep upper limits favor a double-degenerate (DD) scenario{\mdash}involving two WD stars{\mdash}for the progenitor system of SN 2014J, as such systems have less circumstellar gas than our upper limits. By contrast, most single-degenerate (SD) scenarios, i.e., the wide family of progenitor systems where a red giant, main-sequence, or sub-giant star donates mass to an exploding WD, are ruled out by our observations. (While completing our work, we noticed that a paper by Margutti et al. was submitted to The Astrophysical Journal. From a non-detection of X-ray emission from SN 2014J, the authors obtain limits of $\backslash$dot$\{$M$\}$ $\backslash$lesssim 1.2 $\backslash$times 10\^{}$\{$-9$\}$ M $_{\&sun;}$ yr$^{-1}$ (for a wind speed of 100 km s$^{-1}$) and n $_{ISM}$ {\l}t}\~{} 3.5 cm$^{-3}$, for the {$\rho$}vpropr $^{-2}$ wind and constant density cases, respectively. As these limits are less constraining than ours, the findings by Margutti et al. do not alter our conclusions. The X-ray results are, however, important to rule out free-free and synchrotron self-absorption as a reason for the radio non-detections.) Our estimates on the limits on the gas density surrounding SN2011fe, using the flux density limits from Chomiuk et al., agree well with their results. Although we discuss the possibilities of an SD scenario passing observational tests, as well as uncertainties in the modeling of the radio emission, the evidence from SNe 2011fe and 2014J points in the direction of a DD scenario for both.}, keywords = {stars: mass-loss, supernovae: individual: SN2011fe SN2014J}, doi = {10.1088/0004-637X/792/1/38}, url = {http://adsabs.harvard.edu/abs/2014ApJ...792...38P}, author = {M. A. P{\'e}rez-Torres and Lundqvist, P. and Beswick, R.~J. and Bj{\"o}rnsson, C.~I. and Muxlow, T.~W.~B. and Paragi, Z. and Ryder, S. and Alberdi, A. and Fransson, C. and Marcaide, J.~M. and Mart{\'\i}-Vidal, I. and Ros, E. and Argo, M.~K. and Guirado, J.~C.} } @article {2014ApJ...786..156H, title = {{A Multi-wavelength View of the Central Kiloparsec Region in the Luminous Infrared Galaxy NGC 1614}}, journal = {The Astrophysical Journal}, volume = {786}, year = {2014}, month = {may}, pages = {156}, abstract = {The Luminous Infrared Galaxy NGC 1614 hosts a prominent circumnuclear ring of star formation. However, the nature of the dominant emitting mechanism in its central \~{}100 pc is still under debate. We present sub-arcsecond angular resolution radio, mid-infrared, Pa{$\alpha$}, optical, and X-ray observations of NGC 1614, aimed at studying in detail both the circumnuclear ring and the nuclear region. The 8.4 GHz continuum emission traced by the Very Large Array and the Gemini/T-ReCS 8.7 {$μ$}m emission, as well as the Pa{$\alpha$} line emission, show remarkable morphological similarities within the star-forming ring, suggesting that the underlying emission mechanisms are tightly related. We used a Hubble Space Telescope/NICMOS Pa{$\alpha$} map of similar resolution to our radio maps to disentangle the thermal free-free and non-thermal synchrotron radio emission, from which we obtained the intrinsic synchrotron power law for each individual region within the central kiloparsec of NGC 1614. The radio ring surrounds a relatively faint, steep-spectrum source at the very center of the galaxy, suggesting that the central source is not powered by an active galactic nucleus (AGN), but rather by a compact (r {\l}t}\~{} 90 pc) starburst (SB). Chandra X-ray data also show that the central kiloparsec region is dominated by SB activity, without requiring the existence of an AGN. We also used publicly available infrared data to model-fit the spectral energy distribution of both the SB ring and a putative AGN in NGC 1614. In summary, we conclude that there is no need to invoke an AGN to explain the observed bolometric properties of the galaxy.}, keywords = {galaxies: individual: NGC 1614, galaxies: nuclei, galaxies: starburst, infrared: galaxies, radio continuum: galaxies, supernovae: general}, doi = {10.1088/0004-637X/786/2/156}, url = {http://adsabs.harvard.edu/abs/2014ApJ...786..156H}, author = {R. Herrero-Illana and M. A. P{\'e}rez-Torres and Alonso-Herrero, A. and Alberdi, A. and Colina, L. and Efstathiou, A. and Hern{\'a}ndez-Garc{\'\i}a, L. and Miralles-Caballero, D. and V{\"a}is{\"a}nen, P. and Packham, C.~C. and Rajpaul, V. and Zijlstra, A.~A.} } @article {2014MNRAS.440.1052K, title = {{The nature of supernovae 2010O and 2010P in Arp 299 - I. Near-infrared and optical evolution}}, journal = {Monthly Notices of the Royal Astronomical Society}, volume = {440}, year = {2014}, month = {may}, pages = {1052-1066}, abstract = {We present near-infrared and optical photometry, plus optical spectroscopy of two stripped-envelope supernovae (SNe) 2010O and 2010P that exploded in two different components of an interacting luminous infrared galaxy Arp 299 within only a few days of one another. SN 2010O is found to be photometrically and spectroscopically similar to many normal Type Ib SNe and our multiwavelength observations of SN 2010P suggest it to be a Type IIb SN. No signs of clear hydrogen features or interaction with the circumstellar medium are evident in the optical spectrum of SN 2010P. We derive estimates for the host galaxy line-of-sight extinctions for both SNe, based on both light curve and spectroscopic comparison finding consistent results. These methods are also found to provide much more robust estimates of the SN host galaxy reddening than the commonly used empirical relations between extinction and equivalent width of Na I D absorption features. The SN observations also suggest that different extinction laws are present in different components of Arp 299. For completeness, we study high-resolution pre-explosion images of Arp 299 and find both SNe to be close to, but not coincident with, extended sources that are likely massive clusters. A very simple model applied to the bolometric light curve of SN 2010O implies a rough estimate for the explosion parameters of E$_{k}$ {\ap} 3 {\times} 10$^{51}$ erg, M$_{ej}$ {\ap} 2.9 M$_{\&sun;}$ and M$_{Ni}$ {\ap} 0.16 M$_{\&sun;}$.}, keywords = {galaxies: individual: Arp 299, galaxies: starburst, infrared: galaxies, supernovae: general, supernovae: individual: SN 2010O, supernovae: individual: SN 2010P}, doi = {10.1093/mnras/stt2289}, url = {http://adsabs.harvard.edu/abs/2014MNRAS.440.1052K}, author = {Kankare, E. and Mattila, S. and Ryder, S. and Fraser, M. and Pastorello, A. and Elias-Rosa, N. and Romero-Ca{\~n}izales, C. and Alberdi, A. and Hentunen, V.-P. and R. Herrero-Illana and Kotilainen, J. and M. A. P{\'e}rez-Torres and V{\"a}is{\"a}nen, P.} } @article {2014MNRAS.440.1067R, title = {{The nature of supernovae 2010O and 2010P in Arp 299 - II. Radio emission}}, journal = {Monthly Notices of the Royal Astronomical Society}, volume = {440}, year = {2014}, pages = {1067-1079}, abstract = {We report radio observations of two stripped-envelope supernovae (SNe), 2010O and 2010P, which exploded within a few days of each other in the luminous infrared galaxy Arp 299. Whilst SN 2010O remains undetected at radio frequencies, SN 2010P was detected (with an astrometric accuracy better than 1 milli arcsec in position) in its optically thin phase in epochs ranging from {\tilde}1 to {\tilde}3 yr after its explosion date, indicating a very slow radio evolution and a strong interaction of the SN ejecta with the circumstellar medium. Our late-time radio observations towards SN 2010P probe the dense circumstellar envelope of this SN, and imply dot$\{$M$\}$ [ $\{$M\_$\{${\sun}$\}$ yr\^{}$\{$-1$\}$$\}$] / v\_$\{$wind$\}$ [10 km s\^{}$\{$-1$\}$] =(3.0-5.1) {\times} 10$^{-5}$, with a 5 GHz peak luminosity of {\tilde}1.2 {\times} 10$^{27}$ erg s$^{- 1}$ Hz$^{- 1}$ on day {\tilde}464 after explosion. This is consistent with a Type IIb classification for SN 2010P, making it the most distant and most slowly evolving Type IIb radio SN detected to date.}, keywords = {galaxies: individual: Arp 299, galaxies: starburst, radio continuum: galaxies, supernovae: general, supernovae: individual: SN 2010O, supernovae: individual: SN 2010P}, doi = {10.1093/mnras/stu430}, url = {http://adsabs.harvard.edu/abs/2014MNRAS.440.1067R}, author = {Romero-Ca{\~n}izales, C. and R. Herrero-Illana and M. A. P{\'e}rez-Torres and Alberdi, A. and Kankare, E. and Bauer, F.~E. and Ryder, S.~D. and Mattila, S. and Conway, J.~E. and Beswick, R.~J. and Muxlow, T.~W.~B.} } @article {2014A\&A...567A..21S, title = {{Properties of bow-shock sources at the Galactic center}}, journal = {Astronomy and Astrophysics}, volume = {567}, year = {2014}, pages = {A21}, abstract = {Context. There exists an enigmatic population of massive stars around the Galactic center (GC) that were formed some Myr ago. A fraction of these stars has been found to orbit the supermassive black hole, Sgr A*, in a projected clockwise disk-like structure, which suggests that they were formed in a formerly existing dense disk around Sgr A*.
Aims: We focus on a subgroup of objects, the extended, near-infrared (NIR) bright sources IRS 1W, IRS 5, IRS 10W, and IRS 21, that have been suggested to be young, massive stars that form bow shocks through their interaction with the interstellar medium (ISM). Their nature has impeded accurate determinations of their orbital parameters. We aim at establishing their nature and kinematics to test whether they form part of the clockwise disk.
Methods: We performed NIR multiwavelength imaging with NACO/VLT using direct adaptive optics (AO) and AO-assisted sparse aperture masking (SAM). We introduce a new method for self-calibration of the SAM point spread function in dense stellar fields. The emission mechanism, morphology, and kinematics of the targets were examined via 3D models, combined with existing models of the gas flow in the central parsec.
Results: We confirm previous findings that IRS 21, IRS 1W, and IRS 5 are bow-shocks created by the interaction between mass-losing stars and the interstellar gas. The nature of IRS 10W remains unclear. Our modeling shows that the bow-shock emission is caused by thermal emission, while the scattering of stellar light does not play a significant role. IRS 1W shows a morphology that is consistent with a bow shock produced by an anisotropic stellar wind or by locally inhomogeneous ISM density. Our best-fit models provide estimates of the local proper motion of the ISM in the Northern Arm that agree with previously published models that were based on radio interferometry and NIR spectroscopy. Assuming that all of the sources are gravitationally tied to Sagittarius A*, their orbital planes were obtained via a Monte Carlo simulation.
Conclusions: Our sources appear to be Wolf-Rayet stars associated to the last starburst at the GC. Our orbital analysis suggests that they are not part of any of the previously suggested coherent stellar structures, in particular the clockwise disk. We thus add more evidence to recent findings that a large proportion of the massive stars show apparently random orbital orientations, suggesting either that not all of them were formed in the clockwise disk, or that their orbits were randomized rapidly after formation in the disk. Appendix A is available in electronic form at http://www.aanda.org}, keywords = {circumstellar matter, Galaxy: center, outflows, stars: winds, techniques: high angular resolution, techniques: interferometric}, doi = {10.1051/0004-6361/201423657}, url = {http://adsabs.harvard.edu/abs/2014A\%26A...567A..21S}, author = {J. Sanchez-Bermudez and Sch{\"o}del, R. and Alberdi, A. and Muzi{\'c}, K. and Hummel, C.~A. and Pott, J.-U.} } @article {2014A\&A...572L...1S, title = {{Resolving the stellar components of the massive multiple system Herschel 36 with AMBER/VLTI}}, journal = {Astronomy and Astrophysics}, volume = {572}, year = {2014}, pages = {L1}, abstract = {Context. Massive stars are extremely important for the evolution of the galaxies; there are large gaps in our understanding of their properties and formation, however, mainly because they evolve rapidly, are rare, and distant. Recent findings suggest that most O-stars belong to multiple systems. It may well be that almost all massive stars are born as triples or higher multiples, but their large distances require very high angular resolution to directly detect the companions at milliarcsecond scales.
Aims: Herschel 36 is a young massive system located at 1.3 kpc. It has a combined smallest predicted mass of 45 M$_{\&sun;}$. Multi-epoch spectroscopic data suggest the existence of at least three gravitationally bound components. Two of them, system Ab, are tightly bound in a spectroscopic binary, and the third one, component Aa, orbits in a wider orbit. Our aim was to image and obtain astrometric and photometric measurements of components Aa and Ab using, for the first time, long-baseline optical interferometry to further constrain its nature.
Methods: We observed Herschel 36 with the near-infrared instrument AMBER attached to the ESO VLT Interferometer, which provides an angular resolution of \~{}2 mas. We used the code BSMEM to perform the interferometric image reconstruction. We fitted the interferometric observables using proprietary IDL routines and the code LitPro.
Results: We imaged the Aa + Ab components of Herschel 36 in H and K filters. Component Ab is located at a projected distance of 1.81 mas, at a position angle of \~{}222{\deg} east of north, the flux ratio between components Aa and Ab is close to one. These findings agree with previous predictions about the properties of Herschel 36. The small measured angular separation indicates that system Ab and Ab may be approaching the periastron of their orbits. These results, only achievable with long-baseline near-infrared interferometry, constitute the first step toward a thorough understanding of this massive triple system.}, keywords = {binaries: close, instrumentation: high angular resolution, instrumentation: interferometers, stars: massive}, doi = {10.1051/0004-6361/201424901}, url = {http://adsabs.harvard.edu/abs/2014A\%26A...572L...1S}, author = {J. Sanchez-Bermudez and Alberdi, A. and Sch{\"o}del, R. and Hummel, C.~A. and Arias, J.~I. and Barb{\'a}, R.~H. and Ma{\'\i}z Apell{\'a}niz, J. and Pott, J.-U.} } @article {2013A\&A...554L...4S, title = {{Direct detection of the tertiary component in the massive multiple HD 150136 with VLTI}}, journal = {Astronomy and Astrophysics}, volume = {554}, year = {2013}, pages = {L4}, abstract = {Context. Massive stars are of fundamental importance for almost all aspects of astrophysics, but there still exist large gaps in our understanding of their properties and formation because they are rare and therefore distant. It has been found that most O-stars are multiples. It may well be that almost all massive stars are born as triples or higher multiples, but their large distances require milliarcsecond angular resolution for a direct detection of the companions.
Aims: HD 150136 is the nearest system to Earth with {\gt}100 M$_{\&sun;}$ and provides a unique opportunity to study an extremely massive system. Recently, evidence for the existence of a third component in HD 150136, in addition to the tight spectroscopic binary that forms the main component, was found in spectroscopic observations. Our aim was to image and obtain astrometric and photometric measurements of this component using long-baseline optical interferometry to further constrain the nature of this component.
Methods: We observed HD 150136 with the near-infrared instrument AMBER attached to the ESO VLT Interferometer, which provides an angular resolution of 2 mas. The recovered closure phases are robust to systematic errors and provide unique information on the source asymmetry. Therefore, they are of crucial relevance for both image reconstruction and model fitting of the source structure.
Results: The third component in HD 150136 is clearly detected in the high-quality data from AMBER. It is located at a projected angular distance of 7.3 mas, or about 13 AU at the line-of-sight distance of HD 150136, at a position angle of 209 degrees east of north, and has a flux ratio of 0.25 with respect to the inner binary. Our findings agree with previous results and have permitted us to improve the orbital solutions of the tertiary around the inner system.
Conclusions: We resolved the third component of HD 150136 in J, H and K filters. The luminosity and color of the tertiary agrees with the predictions and shows that it is also an O main-sequence star. The small measured angular separation indicates that the tertiary may be approaching the periastron of its orbit. These results, only achievable with long-baseline near-infrared interferometry, constitute the first step toward understanding the massive star formation mechanisms.}, keywords = {binaries: general, instrumentation: high angular resolution, instrumentation: interferometers, stars: massive}, doi = {10.1051/0004-6361/201321649}, url = {http://adsabs.harvard.edu/abs/2013A\%26A...554L...4S}, author = {J. Sanchez-Bermudez and Sch{\"o}del, R. and Alberdi, A. and Barb{\'a}, R.~H. and Hummel, C.~A. and Ma{\'\i}z Apell{\'a}niz, J. and Pott, J.-U.} } @article {2013PASA...30....3D, title = {{GASKAP-The Galactic ASKAP Survey}}, journal = {Publications of the Astronomical Society of Australia}, volume = {30}, year = {2013}, month = {jan}, pages = {3}, abstract = {A survey of the Milky Way disk and the Magellanic System at the wavelengths of the 21-cm atomic hydrogen (HI) line and three 18-cm lines of the OH molecule will be carried out with the Australian Square Kilometre Array Pathfinder telescope. The survey will study the distribution of HI emission and absorption with unprecedented angular and velocity resolution, as well as molecular line thermal emission, absorption, and maser lines. The area to be covered includes the Galactic plane (|b| {\l}t} 10{\deg}) at all declinations south of {$δ$} = +40{\deg}, spanning longitudes 167{\deg} through 360{\deg}to 79{\deg} at b = 0{\deg}, plus the entire area of the Magellanic Stream and Clouds, a total of 13 020 deg$^{2}$. The brightness temperature sensitivity will be very good, typically {$\sigma$}$_{T}${\sime} 1 K at resolution 30 arcsec and 1 km s$^{-1}$. The survey has a wide spectrum of scientific goals, from studies of galaxy evolution to star formation, with particular contributions to understanding stellar wind kinematics, the thermal phases of the interstellar medium, the interaction between gas in the disk and halo, and the dynamical and thermal states of gas at various positions along the Magellanic Stream.}, keywords = {Galaxy: evolution, Galaxy: general, ISM: clouds, ISM: general, ISM: kinematics and dynamics, ISM: molecules}, doi = {10.1017/pasa.2012.003}, url = {http://adsabs.harvard.edu/abs/2013PASA...30....3D}, author = {Dickey, J.~M. and McClure-Griffiths, N. and Gibson, S.~J. and G{\'o}mez, J.~F. and Imai, H. and Jones, P. and Stanimirovi{\'c}, S. and Van Loon, J.~T. and Walsh, A. and Alberdi, A. and Anglada, G. and Uscanga, L. and Arce, H. and Bailey, M. and Begum, A. and Wakker, B. and Bekhti, N.~B. and Kalberla, P. and Winkel, B. and Bekki, K. and For, B.-Q. and Staveley-Smith, L. and Westmeier, T. and Burton, M. and Cunningham, M. and Dawson, J. and Ellingsen, S. and Diamond, P. and Green, J.~A. and Hill, A.~S. and Koribalski, B. and McConnell, D. and Rathborne, J. and Voronkov, M. and Douglas, K.~A. and English, J. and Ford, H.~A. and Lockman, F.~J. and Foster, T. and Gomez, Y. and Green, A. and Bland-Hawthorn, J. and Gulyaev, S. and Hoare, M. and Joncas, G. and Kang, J.-H. and Kerton, C.~R. and Koo, B.-C. and Leahy, D. and Lo, N. and Migenes, V. and Nakashima, J. and Zhang, Y. and Nidever, D. and Peek, J.~E.~G. and Tafoya, D. and Tian, W. and Wu, D.} } @article {2012ApJ...744L..19K, title = {{Discovery of Two Supernovae in the Nuclear Regions of the Luminous Infrared Galaxy IC 883}}, journal = {The Astrophysical Journal Letters}, volume = {744}, year = {2012}, pages = {L19}, abstract = {We report the discovery of two consecutive supernovae (SNe), 2010cu and 2011hi, located at 0farcs37 (180 pc) and 0farcs79 (380 pc) projected distance, respectively, from the center of the K-band nucleus of the luminous infrared galaxy (LIRG) IC 883. The SNe were discovered in an ongoing near-infrared K-band search for core-collapse SNe in such galaxies using the ALTAIR/NIRI adaptive optics system with laser guide star at the Gemini-North Telescope. These are thus the closest SNe yet discovered to an LIRG nucleus in optical or near-infrared wavelengths. The near-infrared light curves and colors of both SNe are consistent with core-collapse events. Both SNe seem to suffer from relatively low host galaxy extinction suggesting that regardless of their low projected galactocentric distances, they are not deeply buried in the nuclear regions of the host galaxy.}, keywords = {galaxies: individual: IC 883, galaxies: starburst, infrared: galaxies, instrumentation: adaptive optics, supernovae: individual: SN 2010cu SN 2011hi}, doi = {10.1088/2041-8205/744/2/L19}, url = {http://adsabs.harvard.edu/abs/2012ApJ...744L..19K}, author = {Kankare, E. and Mattila, S. and Ryder, S. and V{\"a}is{\"a}nen, P. and Alberdi, A. and Alonso-Herrero, A. and Colina, L. and Efstathiou, A. and Kotilainen, J. and Melinder, J. and M. A. P{\'e}rez-Torres and Romero-Ca{\~n}izales, C. and Takalo, A.} } @article {2012A\&A...543A..72R, title = {{e-MERLIN and VLBI observations of the luminous infrared galaxy IC 883: a nuclear starburst and an AGN candidate revealed}}, journal = {Astronomy and Astrophysics}, volume = {543}, year = {2012}, month = {jul}, pages = {A72}, abstract = {Context. The high star formation rates of luminous infrared galaxies (LIRGs) make them ideal places for core-collapse supernova (CCSN) searches. Massive star formation can often be found in coexistence with an active galactic nucleus (AGN), contributing jointly to the energy source of LIRGs. At radio frequencies, where light is unaffected by dust extinction, it is possible to detect compact components within the innermost LIRG nuclear regions, such as SNe and SN remnants, as well as AGN buried deep in the LIRG nuclei.
Aims: Our study of the LIRG IC 883 aims at: (i) investigating the parsec-scale radio structure of the (circum-)nuclear regions of IC 883; (ii) detecting at radio frequencies the two recently reported circumnuclear SNe 2010cu and 2011hi, which were discovered by near-IR (NIR) adaptive optics observations of IC 883; and (iii) further investigating the nature of SN 2011hi at NIR wavelengths.
Methods: We used the electronic European very long baseline interferometry (VLBI) Network (e-EVN) at 5 GHz, and the electronic Multi-Element Remotely Linked Interferometer Network (e-MERLIN) at 6.9 GHz, to observe contemporaneously the LIRG IC 883 at high angular-resolution (from tens to hundreds of milliarcsec) and with high sensitivity ({\l}t}70 {$μ$}Jy), complemented by archival VLBI data at 5 GHz and 8.4 GHz. We also used the Gemini North telescope to obtain late-time JHK photometry for SN 2011hi.
Results: The circumnuclear regions traced by e-MERLIN at 6.9 GHz have an extension of \~{} 1 kpc, at a position angle of 130{\deg}, and show a striking double-sided structure, which very likely corresponds to a warped rotating ring, in agreement with previous studies. Our e-EVN observations at 5 GHz and complementary archival VLBI data at 5 GHz and 8.4 GHz, reveal various milliarcsec compact components in the nucleus of IC 883. A single compact source, an AGN candidate, dominates the emission at both nuclear and circumnuclear scales, as imaged with the e-EVN and e-MERLIN, respectively. The other milliarcsec components are strongly indicative of ongoing nuclear CCSN activity. Our e-EVN observations also provided upper limits to the radio luminosity of the two SNe in IC 883 recently discovered at NIR wavelengths. We refine the classification of SN 2011hi as a Type IIP SN according to our latest epoch of Gemini North observations acquired in 2012, in agreement with a low-luminosity radio SN nature. We estimate a CCSN rate lower limit of 1.1$_{-0.6}$$^{+1.3}$ yr$^{-1}$ for the entire galaxy, based on three nuclear radio SNe and the circumnuclear SNe 2010cu and 2011hi.}, keywords = {galaxies: individual: IC 883, galaxies: starburst, radiation mechanisms: non-thermal, radio lines: stars}, doi = {10.1051/0004-6361/201218816}, url = {http://adsabs.harvard.edu/abs/2012A\%26A...543A..72R}, author = {Romero-Ca{\~n}izales, C. and M. A. P{\'e}rez-Torres and Alberdi, A. and Argo, M.~K. and Beswick, R.~J. and Kankare, E. and Batejat, F. and Efstathiou, A. and Mattila, S. and Conway, J.~E. and Garrington, S.~T. and Muxlow, T.~W.~B. and Ryder, S.~D. and V{\"a}is{\"a}nen, P.} } @article {2012A\&A...540L...5H, title = {{Evidence of nuclear disks in starburst galaxies from their radial distribution of supernovae}}, journal = {Astronomy and Astrophysics}, volume = {540}, year = {2012}, pages = {L5}, abstract = {Galaxy-galaxy interactions are expected to be responsible for triggering massive star formation and possibly accretion onto a supermassive black hole, by providing large amounts of dense molecular gas down to the central kiloparsec region. Several scenarios to drive the gas further down to the central \~{}100 pc, have been proposed, including the formation of a nuclear disk around the black hole, where massive stars would produce supernovae. Here, we probe the radial distribution of supernovae and supernova remnants in the nuclear regions of the starburst galaxies M 82, Arp 299-A, and Arp 220, by using high-angular resolution ({\l}sim} 0.{\textquoteright}{\textquoteright}1) radio observations published in the literature (for M 82 and Arp 220), or obtained by ourselves from the European VLBI Network (Arp 299-A). Our main goal was to characterize the nuclear starbursts in those galaxies and thus test scenarios that propose that nuclear disks of sizes \~{}100 pc form in the central regions of starburst galaxies. We obtained the radial distribution of supernovae (SNe) in the nuclear starbursts of M 82, Arp 299-A, and Arp 220, and derived scale-length values for the putative nuclear disks powering the bursts in those central regions. The scale lengths for the (exponential) disks range from \~{}20-30 pc for Arp 299-A and Arp 220, up to \~{}140 pc for M 82. The radial distribution of SNe for the nuclear disks in Arp 299-A and Arp 220 is also consistent with a power-law surface density profile of exponent {$\gamma$} = 1, as expected from detailed hydrodynamical simulations of nuclear disks. Our results support scenarios where a nuclear disk of size \~{}100 pc is formed in (U)LIRGs, and sustained by gas pressure, in which case the accretion onto the black hole could be lowered by supernova feedback. Appendices are available in electronic form at http://www.aanda.org}, keywords = {galaxies: individual: Arp 299-A, galaxies: luminosity function, galaxies: starburst, mass function, radiation mechanisms: non-thermal, radio continuum: stars, supernovae: general}, doi = {10.1051/0004-6361/201118545}, url = {http://adsabs.harvard.edu/abs/2012A\%26A...540L...5H}, author = {R. Herrero-Illana and M. A. P{\'e}rez-Torres and Alberdi, A.} } @article {2012MNRAS.422..510R, title = {{EVN observations of the farthest and brightest ULIRGs in the local Universe: the case of IRAS 23365+3604}}, journal = {Monthly Notices of the Royal Astronomical Society}, volume = {422}, year = {2012}, month = {may}, pages = {510-520}, abstract = {We present high-resolution, high-sensitivity radio images of the ultra-luminous infrared galaxy (ULIRG) IRAS 23365+3604. We performed contemporaneous observations at 1.7 and 5.0 GHz, in three epochs separated by 1 year from each other, with the European Very Long Baseline Interferometry (VLBI) Network (EVN). We also present complementary Multi-Element Radio Linked Interferometry Network (MERLIN) at 1.6 and 5.0 GHz, and archival Very Large Array data, taken at 1.4 and 4.9 GHz. We find that the emission at {\tilde}5.0 GHz remains quite compact as seen at different resolutions, whereas at {\tilde}1.7 GHz, high-resolution imaging reveals some extended structure. The nuclear region has an approximate linear size of 200 pc and shows the presence of two main emission components: (i) one with a composite spectrum due to ongoing non-thermal activity (probably due to recently exploded supernovae and the presence of an active galactic nucleus), and (ii) the other with a steep spectrum, likely dominated by an old population of radio emitters, such as supernova remnants. Radiative losses are important, so re-acceleration or replenishment of new electrons is necessary. We estimate a magnetic field strength of {\tilde} 18 {$μ$}G at galactic and {\tilde} 175 {$μ$}G at nuclear scales, which are typical for galaxies in advanced mergers.}, keywords = {galaxies: individual: IRAS 23365+3604, galaxies: starburst, radio continuum: general}, doi = {10.1111/j.1365-2966.2012.20627.x}, url = {http://adsabs.harvard.edu/abs/2012MNRAS.422..510R}, author = {Romero-Ca{\~n}izales, C. and M. A. P{\'e}rez-Torres and Alberdi, A.} } @article {2012JPhCS.372a2025S, title = {{NaCo/SAM observations of sources at the Galactic Center}}, journal = {Journal of Physics Conference Series}, volume = {372}, number = {1}, year = {2012}, month = {jul}, pages = {012025}, abstract = {Sparse aperture masking (SAM) interferometry combined with Adaptive Optics (AO) is a technique that is uniquely suited to investigate structures near the diffraction limit of large telescopes. The strengths of the technique are a robust calibration of the Point Spread Function (PSF) while maintaining a relatively high dynamic range. We used SAM+AO observations to investigate the circumstellar environment of several bright sources with infrared excess in the central parsec of the Galaxy. For our observations, unstable atmospheric conditions as well as significant residuals after the background subtraction presented serious problems for the standard approach of calibrating SAM data via interspersed observations of reference stars. We circumvented these difficulties by constructing a synthesized calibrator directly from sources within the field-of-view. When observing crowded fields, this novel method can boost the efficiency of SAM observations because it renders interspersed calibrator observations unnecessary. Here, we presented the first NaCo/SAM images reconstructed using this method.}, doi = {10.1088/1742-6596/372/1/012025}, url = {http://adsabs.harvard.edu/abs/2012JPhCS.372a2025S}, author = {J. Sanchez-Bermudez and Sch{\"o}del, R. and Alberdi, A. and Pott, J.~U.} } @article {2012A\&A...539A.134B, title = {{The nuclear starburst in Arp 299-A: from the 5.0 GHz VLBI radio light-curves to its core-collapse supernova rate}}, journal = {Astronomy and Astrophysics}, volume = {539}, year = {2012}, pages = {A134}, abstract = {Context. The nuclear region of the luminous infrared galaxy (LIRG) Arp 299-A hosts a recent ( {\sime} 10 Myr) intense burst of massive star formation that is expected to lead to numerous core-collapse supernovae (CCSNe). Previous VLBI observations, carried out with the European VLBI Network (EVN) at 5.0 GHz and with the VLBA at 2.3 and 8.4 GHz, resulted in the detection of many compact, bright, non-thermal sources in a region {\l}sim} 150 pc in size.
Aims: We aim to establish the nature of all non-thermal compact components in Arp 299-A, as well as to estimate its core-collapse supernova rate. While the majority of the compact components are expected to be young radio supernovae (RSNe) and supernova remnants (SNRs), a definitive classification is still lacking. Yet, this is very relevant for eventually establishing the CCSN rate, as well as the star formation rate, for this galaxy.
Methods: We used multi-epoch EVN observations taken at 5.0 GHz to image the compact radio sources in the nuclear region of Arp 299-A with milliarcsecond resolution. We also used one single-epoch 5.0 GHz Multi-Element Radio Linked Interferometer Network (MERLIN) observation to image the extended emission in which these compact radio sources are embedded.
Results: We present the first 5.0 GHz radio light-curve (spanning \~{}2.5 yr) of all compact components in the nuclear starburst of Arp 299-A. Twenty-six compact sources are detected, eight of which are new objects. The properties of all detected objects are consistent with them being a mixed population of CCSNe and SNRs. We find clear evidence for at least two new CCSNe, implying a lower limit to the CCSN rate of {$ν$}$_{SN}$ {\gsim} 0.80 SN/yr, indicating that the bulk of the current star formation in Arp 299-A is taking place in the innermost \~{}150 pc.A few more objects show variability consistent with them being recently exploded SNe, but only future observations will clarify this point. Our MERLIN observations trace a region of diffuse extended emission that is cospatial to the region where all compact sources are found. From this diffuse non-thermal radio emission traced by MERLIN we obtain an independent estimate for the CCSN rate, which is in the range {$ν$}$_{SN}$ = 0.40-0.65 SN/yr, in agreement with previous estimates and our direct estimate of the CCSN rate from the compact radio emission.
Conclusions: Our \~{}2.5 yr monitoring of Arp 299-A has allowed us to obtain for the first time a direct estimate of the CCSN rate of {$ν$}$_{SN}$ {\gsim} 0.80 SN/yr for the innermost \~{}150 pc of Arp 299-A.}, keywords = {galaxies: individual: Arp 299, galaxies: luminosity function, galaxies: starburst, mass function, radiation mechanisms: non-thermal, radio continuum: stars, supernovae: general}, doi = {10.1051/0004-6361/201118446}, url = {http://adsabs.harvard.edu/abs/2012A\%26A...539A.134B}, author = {Bondi, M. and M. A. P{\'e}rez-Torres and R. Herrero-Illana and Alberdi, A.} } @article {2011MNRAS.415.2688R, title = {{The core-collapse supernova rate in Arp 299 revisited}}, journal = {Monthly Notices of the Royal Astronomical Society}, volume = {415}, year = {2011}, pages = {2688-2698}, abstract = {We present a study of the core-collapse supernova (CCSN) rate in nuclei A and B1, of the luminous infrared galaxy (LIRG) Arp 299, based on {\tilde}11 yr of Very Large Array (VLA) monitoring of their radio emission at 8.4 GHz. Significant variations in the nuclear radio flux density can be used to identify the CCSN activity in the absence of high-resolution very long baseline interferometry (VLBI) observations. In the case of the B1-nucleus, the small variations in its measured diffuse (synchrotron plus free-free) radio emission are below the fluxes expected from radio supernovae (RSNe), thus making it well-suited to detect RSNe through flux density variability. In fact, we find strong evidence for at least three RSNe this way, which results in a lower limit for the CCSN rate ({$ν$}$_{SN}$) of {\gt}0.28$^{+0.27}$$_{-0.15}$ yr$^{-1}$. This value agrees within the uncertainties with the infrared (IR) luminosity based SN rate estimate, and with previously reported radio estimates. In the A-nucleus, we did not detect any significant variability and found a SN detection threshold luminosity of {\ap}3.1 {\times} 10$^{28}$ erg s$^{-1}$ Hz$^{-1}$, allowing only the detection of the most luminous RSNe known. Our method is basically blind to normal CCSN explosions occurring within the A-nucleus, which result in too small variations in the nuclear flux density, remaining diluted by the strong diffuse emission of the nucleus itself. Additionally, we have attempted to find near-IR (NIR) counterparts for the earlier reported RSNe in the Arp 299 nucleus A, by comparing NIR adaptive optics images from the Gemini-N Telescope with contemporaneous observations from the European VLBI Network (EVN). However, we were not able to detect NIR counterparts for the reported radio SNe within the innermost regions of nucleus A. While our NIR observations were sensitive to typical CCSNe at {\tilde}300 mas (or 70 pc projected distance) from the centre of the nucleus A, suffering from extinction up to A$_{V}${\tilde} 15 mag, they were not sensitive to such highly obscured SNe within the innermost nuclear regions where most of the EVN sources were detected.}, keywords = {galaxies: individual: NGC 3690:IC 694, galaxies: starburst, supernovae: general}, doi = {10.1111/j.1365-2966.2011.18886.x}, url = {http://adsabs.harvard.edu/abs/2011MNRAS.415.2688R}, author = {Romero-Ca{\~n}izales, C. and Mattila, S. and Alberdi, A. and M. A. P{\'e}rez-Torres and Kankare, E. and Ryder, S.~D.} } @article {2011A\&A...533A.111M, title = {{Detection of jet precession in the active nucleus of M 81}}, journal = {Astronomy and Astrophysics}, volume = {533}, year = {2011}, month = {sep}, pages = {A111}, abstract = {We report on very-long-baseline-interferometry (VLBI) monitoring observations of the low-luminosity active galactic nucleus (LLAGN) in the galaxy M 81 at the frequencies of 1.7, 2.3, 5.0, and 8.4 GHz. The observations reported here are phase-referenced to the supernova SN 1993J (located in the same galaxy) and cover from late 1993 to late 2005. The large amount of available observations allows us to study the stability of the AGN position in the frame of its host galaxy at different frequencies and chromatic effects in the jet morphology, together with their time evolution. The source consists at all frequencies of a slightly resolved core and a small jet extension towards the northeast direction (position angle of \~{}65 degrees) in agreement with previous publications. We find that the position of the intensity peak in the images at 8.4 GHz is very stable in the galactic frame of M 81 (proper motion upper limit about 10 {$μ$}as per year). We confirm previous reports that the peaks at all frequencies are systematically shifted among them, possibly due to opacity effects in the jet as predicted by the standard relativistic jet model. We use this model, under plausible assumptions, to estimate the magnetic field in the jet close to the jet base and the mass of the central black hole. We obtain a black-hole mass of \~{}2 {\times} 10$^{7}$ M$_{\&sun;}$, comparable to estimates previously reported using different approaches, but the magnetic fields obtained are 10$^{3}$-10$^{4}$ times lower than previous estimates. We find that the positions of the cores at 1.7, 2.3, and 5.0 GHz are less stable than that at 8.4 GHz and evolve systematically, shifting southward at a rate of several tens of {$μ$}as per year. The evolution in the jet orientation seems to be related to changes in the inclination of the cores at all frequencies. These results can be interpreted as due to a precessing jet. The evolving jet orientation also seems to be related to a flare in the peak flux densities at 5.0 and 8.4 GHz, which lasts \~{}4 years (from mid 1997 to mid 2001). An increase in the accretion rate of the black hole, and its correlation with the jet luminosity via the disk-jet connection model, seems insufficient to explain this long flare and the simultaneous evolution in the jet orientation. A continued monitoring of the flux density and the jet structure evolution in this LLAGN will be necessary to further confirm our jet precession model.}, keywords = {astrometry, galaxies: active, galaxies: individual: M 81, galaxies: jets, radiation mechanisms: non-thermal, radio continuum: galaxies}, doi = {10.1051/0004-6361/201117211}, url = {http://adsabs.harvard.edu/abs/2011A\%26A...533A.111M}, author = {Mart{\'\i}-Vidal, I. and Marcaide, J.~M. and Alberdi, A. and M. A. P{\'e}rez-Torres and Ros, E. and Guirado, J.~C.} } @article {2011A\&A...532A..83S, title = {{The mean infrared emission of Sagittarius A*}}, journal = {Astronomy and Astrophysics}, volume = {532}, year = {2011}, month = {aug}, pages = {A83}, abstract = {Context. The massive black hole at the center of the Milky Way, Sagittarius A* (Sgr A*) is, in relative terms, the weakest accreting black hole accessible to observations. It has inspired the theoretical models of radiatively inefficient accretion. Unfortunately, our knowledge of the mean SED and source structure of Sgr A* is very limited owing to numerous observational difficulties. At the moment, the mean SED of Sgr A* is only known reliably in the radio to mm regimes.
Aims: The goal of this paper is to provide constraints on the mean emission from Sgr A* in the near-to-mid infrared.
Methods: Sensitive images of the surroundings of Sgr A* at 8.6 {$μ$}m, 4.8 {$μ$}m , and 3.8 {$μ$}m were produced by combining large quantities of imaging data. Images were produced for several observing epochs. Excellent imaging quality was reached in the MIR by using speckle imaging combined with holographic image reconstruction, a novel technique for this kind of data.
Results: No counterpart of Sgr A* is detected at 8.6 {$μ$}m. At this wavelength, Sgr A* is located atop a dust ridge, which considerably complicates the search for a potential point source. An observed 3{$\sigma$} upper limit of \~{}10 mJy is estimated for the emission of Sgr A* at 8.6 {$μ$}m, a tighter limit at this wavelength than in previous work. The de-reddened 3{$\sigma$} upper limit, including the uncertainty of the extinction correction, is \~{}84 mJy . Based on the available data, it is argued that, with currently available instruments, Sgr A* cannot be detected in the MIR, not even during flares. At 4.8 {$μ$}m and 3.8 {$μ$}m, on the other hand, Sgr A* is detected at all times, at least when considering timescales of a few up to 13 min. We derive well-defined time-averaged, de-reddened flux densities of 3.8 {\plusmn} 1.3 mJy at 4.8 {$μ$}m and 5.0 {\plusmn} 0.6 mJy at 3.8 {$μ$}m. Observations with NIRC2/Keck and NaCo/VLT from the literature provide good evidence that Sgr A* also has a fairly well-defined de-reddened mean flux of 0.5-2.5 mJy at wavelengths of 2.1-2.2 {$μ$}m.
Conclusions: We present well-constrained anchor points for the SED of Sgr A* on the high-frequency side of the Terahertz peak. The new data are in general agreement with published theoretical SEDs of the mean emission from Sgr A*, but we expect them to have an appreciable impact on the model parameters in future theoretical work.}, keywords = {black hole physics, Galaxy: center, instrumentation: adaptive optics, instrumentation: high angular resolution}, doi = {10.1051/0004-6361/201116994}, url = {http://adsabs.harvard.edu/abs/2011A\%26A...532A..83S}, author = {Sch{\"o}del, R. and Morris, M.~R. and Muzi{\'c}, K. and Alberdi, A. and Meyer, L. and Eckart, A. and Gezari, D.~Y.} } @article {2011A\&A...531A..52M, title = {{A model for the thermal radio-continuum emission from radiative shocks in colliding stellar winds}}, journal = {Astronomy and Astrophysics}, volume = {531}, year = {2011}, month = {jul}, pages = {A52}, abstract = {Context. In massive-star binary systems, the interaction of the strong stellar winds results in a wind collision region (WCR) between the stars, which is limited by two shock fronts. Besides the nonthermal emission resulting from the shock acceleration, these shocks emit thermal (free-free) radiation detectable at radio frequencies that increase the expected emission from the stellar winds. Observations and theoretical studies of these sources show that the shocked gas is an important, but not dominant, contributor to the total emission in wide binary systems, while it plays a very substantial role in close binaries.
Aims: The interaction of two isotropic stellar winds is studied in order to calculate the free-free emission from the WCR. The effects of the binary separation and the wind momentum ratio on the emission from the wind-wind interaction region are investigated.
Methods: We developed a semi-analytical model for calculating the thermal emission from colliding stellar winds. Assuming radiative shocks for the compressed layer, which are expected in close binaries, we obtained the emission measure of the thin shell. Then, we computed the total optical depth along each line of sight to obtain the emission from the whole configuration.
Results: Here, we present predictions of the free-free emission at radio frequencies from analytic, radiative shock models in colliding wind binaries. It is shown that the emission from the WCR mainly arises from the optically thick region of the compressed layer and scales as \~{}D$^{4/5}$, where D is the binary separation. The predicted flux density S$_{nu}$ from the WCR becomes more important as the frequency {$ν$} increases, showing higher spectral indices than the expected 0.6 value (S$_{nu}$ {\prop} {$ν$}$^{alpha}$, where {$\alpha$} = 0.6) from the unshocked winds. We also investigate the emission from short-period WR+O systems calculated with our analytic formulation. In particular, we apply the model to the binary systems WR 98 and WR 113 and compare our results with the observations. Our theoretical results are in good agreement with the observed thermal spectra from these sources.}, keywords = {binaries: close, radiation mechanisms: thermal, radio continuum: stars, stars: Wolf-Rayet}, doi = {10.1051/0004-6361/201015988}, url = {http://adsabs.harvard.edu/abs/2011A\%26A...531A..52M}, author = {Montes, G. and Gonz{\'a}lez, R.~F. and Cant{\'o}, J. and M. A. P{\'e}rez-Torres and Alberdi, A.} } @article {2011A\&A...528A..30C, title = {{Molecules as tracers of galaxy evolution: an EMIR survey. I. Presentation of the data and first results}}, journal = {Astronomy and Astrophysics}, volume = {528}, year = {2011}, month = {apr}, pages = {A30}, abstract = {
Aims: We investigate the molecular gas properties of a sample of 23 galaxies in order to find and test chemical signatures of galaxy evolution and to compare them to IR evolutionary tracers.
Methods: Observation at 3 mm wavelengths were obtained with the EMIR broadband receiver, mounted on the IRAM 30 m telescope on Pico Veleta, Spain. We compare the emission of the main molecular species with existing models of chemical evolution by means of line intensity ratios diagrams and principal component analysis.
Results: We detect molecular emission in 19 galaxies in two 8 GHz-wide bands centred at 88 and 112 GHz. The main detected molecules are CO, $^{13}$CO, HCN, HNC, HCO$^{+}$, CN, and C$_{2}$H. We also detect HC$_{3}$N J = 10-9 in the galaxies IRAS 17208, IC 860, NGC 4418, NGC 7771, and NGC 1068. The only HC$_{3}$N detections are in objects with HCO$^{+}$/HCN {\l}t} 1. Galaxies with the highest HC$_{3}$N/HCN ratios have warm IRAS colours (60/100 {$μ$}m {\gt} 0.8). The brightest HC$_{3}$N emission is found in IC 860, where we also detect the molecule in its vibrationally excited state. We find low HNC/HCN line ratios ({\l}t}0.5), that cannot be explained by existing PDR or XDR chemical models. The intensities of HCO+ and HNC appear anti-correlated. No correlation is found between the HNC/HCN line ratio and dust temperature. All HNC-bright objects are either luminous IR galaxies (LIRG) or Seyferts. Galaxies with bright polycyclic aromatic hydrocarbons (PAH) emission show low HNC/HCO$^{+}$ ratios. The CO/$^{13}$CO ratio is positively correlated with the dust temperature and is generally higher than in our galaxy. The emission of CN and C$^{18}$O is correlated.
Conclusions: Bright HC$_{3}$N emission in HCO$^{+}$-faint objects may imply that these are not dominated by X-ray chemistry. Thus the HCN/HCO$^{+}$ line ratio is not, by itself, a reliable tracer of XDRs. Bright HC$_{3}$N and faint HCO$^{+}$ could be signatures of embedded star-formation, instead of AGN activity. Mechanical heating caused by supernova explosions may be responsible for the low HNC/HCN and high HCO$^{+}$/HCN ratios in some starbursts. We cannot exclude, however, that the discussed trends are largely caused by optical depth effects or excitation. Chemical models alone cannot explain all properties of the observed molecular emission. Better constraints to the gas spacial distribution and excitation are needed to distinguish abundance and excitation effects. Appendices are only available in electronic form http://www.aanda.org}, keywords = {evolution, galaxies: active, galaxies: evolution, galaxies: ISM, ISM: molecules}, doi = {10.1051/0004-6361/201015628}, url = {http://adsabs.harvard.edu/abs/2011A\%26A...528A..30C}, author = {F. Costagliola and Aalto, S. and M. Rodr{\'\i}guez and Muller, S. and Spoon, H.~W.~W. and Mart{\'\i}n, S. and M. A. P{\'e}rez-Torres and Alberdi, A. and Lindberg, J.~E. and Batejat, F. and J{\"u}tte, E. and van der Werf, P. and Lahuis, F.} } @article {2011A\&A...526A.142M, title = {{Radio emission of SN1993J: the complete picture. I. Re-analysis of all the available VLBI data}}, journal = {Astronomy and Astrophysics}, volume = {526}, year = {2011}, month = {feb}, pages = {A142}, abstract = {We have performed a complete re-calibration and re-analysis of all the available Very-Long-Baseline-Interferometry (VLBI) observations of supernova SN1993J, following an homogeneous and well-defined methodology. VLBI observations of SN1993J at 69 epochs, spanning 13 years, were performed by two teams, which used different strategies and analysis tools. The results obtained by each group are similar, but their conclusions on the supernova expansion and the shape and evolution of the emitting region differ significantly. From our analysis of the combined set of observations, we have obtained an expansion curve with unprecedented time resolution and coverage. We find that the data from both teams are compatible when analyzed with the same methodology. One expansion index (m$_{3}$ = 0.87 {\plusmn} 0.02) is enough to model the expansion observed at 1.7 GHz, while two expansion indices (m$_{1}$ = 0.933 {\plusmn} 0.010 and m$_{2}$ = 0.796 {\plusmn} 0.005), separated by a break time, t$_{br}$ = 390 {\plusmn} 30 days, are needed to model the data, at frequencies higher than 1.7 GHz, up to day \~{}4000 after explosion. We thus confirm the wavelength dependence of the size of the emitting region reported by one of the groups. We also find that all sizes measured at epochs later than day \~{}4000 after explosion are systematically smaller than our model predictions (i.e., an additional expansion index might be needed to properly model these data). We also estimate the fractional shell width (0.31 {\plusmn} 0.02, average of all epochs and frequencies) and the level of opacity to the radio emission by the ejecta. We find evidence of a spectral-index radial gradient in the supernova shell, which is indicative of a frequency-dependent ejecta opacity. Finally, we study the distribution and evolution of the azimuthal anisotropies (hot spots) found around the radio shell during the expansion. These anisotropies have intensities of \~{}20\% of the mean flux density of the shell, and appear to systematically evolve during the expansion.}, keywords = {galaxies: individual: M 81, radio continuum: stars, supernovae: general, supernovae: individual: SN1993J}, doi = {10.1051/0004-6361/200913831}, url = {http://adsabs.harvard.edu/abs/2011A\%26A...526A.142M}, author = {Mart{\'\i}-Vidal, I. and Marcaide, J.~M. and Alberdi, A. and Guirado, J.~C. and M. A. P{\'e}rez-Torres and Ros, E.} } @article {2011A\&A...526A.143M, title = {{Radio emission of SN1993J: the complete picture. II. Simultaneous fit of expansion and radio light curves}}, journal = {Astronomy and Astrophysics}, volume = {526}, year = {2011}, pages = {A143}, abstract = {We report on a simultaneous modelling of the expansion and radio light curves of the supernova SN1993J. We developed a simulation code capable of generating synthetic expansion and radio light curves of supernovae by taking into consideration the evolution of the expanding shock, magnetic fields, and relativistic electrons, as well as the finite sensitivity of the interferometric arrays used in the observations. Our software successfully fits all the available radio data of SN 1993J with a standard emission model for supernovae, which is extended with some physical considerations, such as an evolution in the opacity of the ejecta material, a radial decline in the magnetic fields within the radiating region, and a changing radial density profile for the circumstellar medium starting from day 3100 after the explosion.}, keywords = {acceleration of particles, galaxies: individual: M 81, radiation mechanisms: non-thermal, radio continuum: stars, supernovae: general, supernovae: individual: SN1993J}, doi = {10.1051/0004-6361/201014517}, url = {http://adsabs.harvard.edu/abs/2011A\%26A...526A.143M}, author = {Mart{\'\i}-Vidal, I. and Marcaide, J.~M. and Alberdi, A. and Guirado, J.~C. and M. A. P{\'e}rez-Torres and Ros, E.} } @article {2011BSRSL..80..704M, title = {{Thermal Radio Emission from Radiative Shocks in Colliding Stellar Winds}}, journal = {Bulletin de la Societe Royale des Sciences de Liege}, volume = {80}, year = {2011}, month = {jan}, pages = {704-708}, abstract = {We present a semi-analytic model for computing the thermal radio continuum emission from radiative shocks within colliding wind binaries. Assuming a thin shell approximation, we determine the contribution of the wind collision region (WCR) to the total thermal emission for close binaries. We investigate the effect of the binary separation and the stellar wind parameters on the total spectrum. In addition, we point out the relevance of taking into account this contribution for the correct interpretation of the observations, and the accuracy of the stellar wind parameters derived from them.}, url = {http://adsabs.harvard.edu/abs/2011BSRSL..80..704M}, author = {Montes, G. and Gonz{\'a}lez, R.~F. and Cant{\'o}, J. and M. A. P{\'e}rez-Torres and Alberdi, A.} } @article {2011A\&A...535L..10M, title = {{VLBI observations of SN 2011dh: imaging of the youngest radio supernova}}, journal = {Astronomy and Astrophysics}, volume = {535}, year = {2011}, pages = {L10}, abstract = {We report on the VLBI detection of supernova SN 2011dh at 22 GHz using a subset of the EVN array. The observations took place 14 days after the discovery of the supernova, thus resulting in a VLBI image of the youngest radio-loud supernova ever. We provide revised coordinates for the supernova with milli-arcsecond precision, linked to the ICRF. The recovered flux density is a factor \~{}2 below the EVLA flux density reported by other authors at the same frequency and epoch of our observations. This discrepancy could be due to extended emission detected with the EVLA or to calibration problems in the VLBI and/or EVLA observations.}, keywords = {ISM: supernova remnants, radiation mechanisms: non-thermal, radio continuum: general, supernovae: general, supernovae: individual: SN 2011dh}, doi = {10.1051/0004-6361/201118195}, url = {http://adsabs.harvard.edu/abs/2011A\%26A...535L..10M}, author = {Mart{\'\i}-Vidal, I. and Tudose, V. and Paragi, Z. and Yang, J. and Marcaide, J.~M. and Guirado, J.~C. and Ros, E. and Alberdi, A. and M. A. P{\'e}rez-Torres and Argo, M.~K. and van der Horst, A.~J. and Garrett, M.~A. and Stockdale, C.~J. and Weiler, K.~W.} } @article {2010A\&A...519L...5P, title = {{Serendipitous discovery of the long-sought active galactic nucleus in Arp 299-A}}, journal = {Astronomy and Astrophysics}, volume = {519}, year = {2010}, month = {sep}, pages = {L5}, abstract = {Context. The dusty nuclear regions of luminous infra-red galaxies (LIRGs) are heated by either an intense burst of massive star formation, an active galactic nucleus (AGN), or a combination of both. Disentangling the contribution of each of those putative dust-heating agents is a challenging task, and direct imaging of the innermost few pc can only be accomplished at radio wavelengths, using very high-angular resolution observations.
Aims: We observed the nucleus A of the interacting starburst galaxy Arp 299, using very long baseline interferometry (VLBI) radio observations at 1.7 and 5.0 GHz. Our aim was to characterize the compact sources in the innermost few pc region of Arp 299-A, as well as to detect recently exploded core-collapse supernovae.
Methods: We used the European VLBI Network (EVN) to image the 1.7 and 5.0 GHz compact radio emission of the parsec-scale structure in the nucleus of Arp 299-A with milliarcsecond resolution.
Results: Our EVN observations show that one of the compact VLBI sources, A1, previously detected at 5.0 GHz, has a flat spectrum between 1.7 and 5.0 GHz and is the brightest source at both frequencies. Our 1.7 GHz EVN image shows also diffuse, low-surface brightness emission extending westwards from A1 and displays a prominent core-jet structure.
Conclusions: The morphology, radio luminosity, spectral index and ratio of radio-to-X-ray emission of the A1-A5 region is consistent with a low-luminosity AGN (LLAGN), and rules out the possibility that it is a chain of young radio supernovae (RSNe) and supernova remnants (SNRs). We therefore conclude that A1-A5 is the long-sought AGN in Arp 299-A. This finding may suggest that both starburst and AGN are frequently associated phenomena in mergers.}, keywords = {galaxies: individual: Arp 299, galaxies: starburst, Galaxy: nucleus, radiation mechanisms: non-thermal, radio continuum: stars}, doi = {10.1051/0004-6361/201015462}, url = {http://adsabs.harvard.edu/abs/2010A\%26A...519L...5P}, author = {M. A. P{\'e}rez-Torres and Alberdi, A. and Romero-Ca{\~n}izales, C. and Bondi, M.} }