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[show abstract]
[hide abstract]
ABSTRACT: Supernova remnant (SNR) candidates in the giant spiral galaxy M101 have been
previously identified from ground-based H-alpha and [SII] images. We have used
archival Hubble Space Telescope (HST) H-alpha and broad-band images as well as
stellar photometry of 55 SNR candidates to examine their physical structure,
interstellar environment, and underlying stellar population. We have also
obtained high-dispersion echelle spectra to search for shocked high-velocity
gas in 18 SNR candidates, and identified X-ray counterparts to SNR candidates
using data from archival observations made by the Chandra X-ray Observatory.
Twenty-one of these 55 SNR candidates studied have X-ray counterparts, although
one of them is a known ultra-luminous X-ray source. The multi-wavelength
information has been used to assess the nature of each SNR candidate. We find
that within this limited sample, ~16% are likely remnants of Type Ia SNe and
~45% are remnants of core-collapse SNe. In addition, about ~36% are large
candidates which we suggest are either superbubbles or OB/HII complexes.
Existing radio observations are not sensitive enough to detect the non-thermal
emission from these SNR candidates. Several radio sources are coincident with
X-ray sources, but they are associated with either giant HII regions in M101 or
background galaxies. The archival HST H-alpha images do not cover the entire
galaxy and thus prevents a complete study of M101. Furthermore, the lack of HST
[SII] images precludes searches for small SNR candidates which could not be
identified by ground-based observations. Such high-resolution images are needed
in order to obtain a complete census of SNRs in M101 for a comprehensive
investigation of the distribution, population, and rates of SNe in this galaxy.
02/2012;
-
P ~M Woods,
J ~M Oliveira,
F Kemper,
J ~T Loon,
B ~A Sargent,
M Matsuura,
R Szczerba,
K Volk,
A ~A Zijlstra,
G ~C Sloan, [......],
I Soszynski,
A ~K Speck,
S Srinivasan,
A ~G ~G ~M Tielens,
E Aarle,
S ~D Dyk,
H Winckel,
U ~P Vijh,
B Whitney,
A ~N Wilkins
VizieR Online Data Catalog. 09/2011; 741:11597.
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Paul M. Woods,
J. M. Oliveira,
F. Kemper,
J. Th. van Loon,
B. A. Sargent,
M. Matsuura,
R. Szczerba,
K. Volk,
A. A. Zijlstra,
G. C. Sloan, [......],
I. Soszyński,
A. K. Speck,
S. Srinivasan,
A. G. G. M. Tielens,
E. van Aarle,
S. D. Van Dyk,
H. Van Winckel,
Uma P. Vijh,
B. Whitney,
A. N. Wilkins
[show abstract]
[hide abstract]
ABSTRACT: We present the classification of 197 point sources observed with the Infrared Spectrograph in the SAGE-Spec Legacy programme on the Spitzer Space Telescope. We introduce a decision-tree method of object classification based on infrared spectral features, continuum and spectral energy distribution shape, bolometric luminosity, cluster membership and variability information, which is used to classify the SAGE-Spec sample of point sources. The decision tree has a broad application to mid-infrared spectroscopic surveys, where supporting photometry and variability information are available. We use these classifications to make deductions about the stellar populations of the Large Magellanic Cloud and the success of photometric classification methods. We find 90 asymptotic giant branch (AGB) stars, 29 young stellar objects, 23 post-AGB objects, 19 red supergiants, eight stellar photospheres, seven background galaxies, seven planetary nebulae, two H ii regions and 12 other objects, seven of which remain unclassified.
Monthly Notices of the Royal Astronomical Society 02/2011; 411(3):1597 - 1627. · 4.90 Impact Factor
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F Kemper,
P ~M Woods,
V Antoniou,
J -P Bernard,
R ~D Blum,
M ~L Boyer,
J Chan, C -H ~R Chen,
M Cohen,
C Dijkstra, [......],
A ~G ~G ~M Tielens,
E Aarle,
S ~D Dyk,
J ~T Loon,
H Winckel,
U ~P Vijh,
K Volk,
B ~A Whitney,
A ~N Wilkins,
A ~A Zijlstra
VizieR Online Data Catalog. 11/2010; 612:20683.
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Paul M. Woods,
J. M. Oliveira,
F. Kemper,
J. Th. van Loon,
B. A. Sargent,
M Matsuura,
R. Szczerba,
K. Volk,
A. A. Zijlstra,
G. C. Sloan, [......],
I. Soszyński,
A. K. Speck,
S. Srinivasan,
A. G. G. M. Tielens,
E. van Aarle,
S. D. Van Dyk,
H. Van Winckel,
Uma P. Vijh,
B. Whitney,
A. N. Wilkins
[show abstract]
[hide abstract]
ABSTRACT: We present the classification of 197 point sources observed with the Infrared Spectrograph in the SAGE-Spec Legacy program on the Spitzer Space Telescope. We introduce a decision-tree method of object classification based on infrared spectral features, continuum and spectral energy distribution shape, bolometric luminosity, cluster membership, and variability information, which is used to classify the SAGE-Spec sample of point sources. The decision tree has a broad application to mid-infrared spectroscopic surveys, where supporting photometry and variability information are available. We use these classifications to make deductions about the stellar populations of the Large Magellanic Cloud and the success of photometric classification methods. We find 90 asymptotic giant branch (AGB) stars, 29 young stellar objects, 23 post-AGB objects, 19 red supergiants, eight stellar photospheres, seven background galaxies, seven planetary nebulae, two HII regions and 12 other objects, seven of which remain unclassified. Comment: (43 pages, 21 figures, 4 tables including one large table out of order; to be published in MNRAS)
09/2010;
-
M. Meixner,
F. Galliano,
S. Hony,
J. Roman-Duval,
T. Robitaille,
P. Panuzzo,
M. Sauvage,
K Gordon,
C. Engelbracht,
K. Misselt, [......],
B. Sargent,
M. Sewiło,
J. D. Simon,
R. Skibba,
L. J. Smith,
S. Srinivasan,
A. G. G. M. Tielens,
J. Th. van Loon,
B. Whitney,
P. M. Woods
[show abstract]
[hide abstract]
ABSTRACT: The HERschel Inventory of The Agents of Galaxy Evolution (HERITAGE) of the Magellanic Clouds will use dust emission to investigate the life cycle of matter in both the Large and Small Magellanic Clouds (LMC and SMC). Using the Herschel Space Observatory's PACS and SPIRE photometry cameras, we imaged a 2x8 square degree strip through the LMC, at a position angle of ~22.5 degrees as part of the science demonstration phase of the Herschel mission. We present the data in all 5 Herschel bands: PACS 100 and 160 {\mu}m and SPIRE 250, 350 and 500 {\mu}m. We present two dust models that both adequately fit the spectral energy distribution for the entire strip and both reveal that the SPIRE 500 {\mu}m emission is in excess of the models by 6 to 17%. The SPIRE emission follows the distribution of the dust mass, which is derived from the model. The PAH-to-dust mass (f_PAH) image of the strip reveals a possible enhancement in the LMC bar in agreement with previous work. We compare the gas mass distribution derived from the HI 21 cm and CO J=1-0 line emission maps to the dust mass map from the models and derive gas-to-dust mass ratios (GDRs). The dust model, which uses the standard graphite and silicate optical properties for Galactic dust, has a very low GDR = 65(+15,-18) making it an unrealistic dust model for the LMC. Our second dust model, which uses amorphous carbon instead of graphite, has a flatter emissivity index in the submillimeter and results in a GDR = 287(+25,-42) that is more consistent with a GDR inferred from extinction. Comment: To be published in Astronomy & Astrophysics, Herschel First Results Issue
06/2010;
-
S. Hony,
F. Galliano,
S. C. Madden,
P. Panuzzo,
M. Meixner,
C. Engelbracht,
K. Misselt,
M. Galametz,
M. Sauvage,
J. Roman-Duval, [......],
A. Bolatto,
K Okumura, C. -H. R. Chen,
R. Indebetouw,
F. P. Israel,
E. Kwon,
A. Li,
F. Kemper,
M. S. Oey,
M. Rubio
[show abstract]
[hide abstract]
ABSTRACT: We study the structure of the medium surrounding sites of high-mass star formation to determine the interrelation between the HII regions and the environment from which they were formed. The density distribution of the surroundings is key in determining how the radiation of the newly formed stars interacts with the surrounds in a way that allows it to be used as a star formation tracer. We present new Herschel/SPIRE 250, 350 and 500 mum data of LHA 120-N44 and LHA 120-N63 in the LMC. We construct average spectral energy distributions (SEDs) for annuli centered on the IR bright part of the star formation sites. The annuli cover ~10-~100 pc. We use a phenomenological dust model to fit these SEDs to derive the dust column densities, characterise the incident radiation field and the abundance of polycyclic aromatic hydrocarbon molecules. We see a factor 5 decrease in the radiation field energy density as a function of radial distance around N63. N44 does not show a systematic trend. We construct a simple geometrical model to derive the 3-D density profile of the surroundings of these two regions. Herschel/SPIRE data have proven very efficient in deriving the dust mass distribution. We find that the radiation field in the two sources behaves very differently. N63 is more or less spherically symmetric and the average radiation field drops with distance. N44 shows no systematic decrease of the radiation intensity which is probably due to the inhomogeneity of the surrounding molecular material and to the complex distribution of several star forming clusters in the region. Comment: Accepted for publication in A&A letters (Herschel special issue)
05/2010;
-
F. Kemper,
Paul M. Woods,
V. Antoniou,
J. -P. Bernard,
R. D. Blum,
M. L. Boyer,
J. Chan, C. -H. R. Chen,
M Cohen,
C. Dijkstra, [......],
A. G. G. M. Tielens,
E. van Aarle,
S. D. Van Dyk,
J. Th. van Loon,
H. Van Winckel,
Uma P. Vijh,
K. Volk,
B. A. Whitney,
A. N. Wilkins,
A. A. Zijlstra
[show abstract]
[hide abstract]
ABSTRACT: The SAGE-Spec Spitzer Legacy program is a spectroscopic follow-up to the SAGE-LMC photometric survey of the Large Magellanic Cloud carried out with the Spitzer Space Telescope. We present an overview of SAGE-Spec and some of its first results. The SAGE-Spec program aims to study the life cycle of gas and dust in the Large Magellanic Cloud, and to provide information essential to the classification of the point sources observed in the earlier SAGE-LMC photometric survey. We acquired 224.6 hours of observations using the InfraRed Spectrograph and the SED mode of the Multiband Imaging Photometer for Spitzer. The SAGE-Spec data, along with archival Spitzer spectroscopy of objects in the Large Magellanic Cloud, are reduced and delivered to the community. We discuss the observing strategy, the specific data reduction pipelines applied and the dissemination of data products to the scientific community. Initial science results include the first detection of an extragalactic "21 um" feature towards an evolved star and elucidation of the nature of disks around RV Tauri stars in the Large Magellanic Cloud. Towards some young stars, ice features are observed in absorption. We also serendipitously observed a background quasar, at a redshift of z~0.14, which appears to be host-less. Comment: 33 pages, 12 figures, 8 tables; accepted for publication by PASP
04/2010;
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M Sewilo,
R Indebetouw,
L ~R Carlson,
B Whitney, C -H ~R Chen,
M Meixner,
T Robitaille,
J ~T Loon,
J ~M Oliveira,
E Churchwell, [......],
P Panuzzo,
M Sauvage,
J Roman-Duval,
K Gordon,
C Engelbracht,
K Misselt,
K Okumura,
T Beck,
J Hora,
P ~M Woods
VizieR Online Data Catalog. 04/2010; 351:89073.
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Paul M Woods,
J M Oliveira,
F Kemper,
J Th Van Loon,
B A Sargent,
M Matsuura,
R Szczerba,
K Volk,
A A Zijlstra,
G C Sloan, [......],
R D Blum,
M Sewi Lo,
D Riebel,
B Shiao, C.-H R Chen,
D Van Dyk,
H Van Winckel,
Uma P Vijh,
B Whitney,
A N Wilkins
[show abstract]
[hide abstract]
ABSTRACT: We present the classification of 197 point sources observed with the Infrared Spectro-graph in the SAGE-Spec Legacy program on the Spitzer Space Telescope. We introduce a decision-tree method of object classification based on infrared spectral features, con-tinuum and spectral energy distribution shape, bolometric luminosity, cluster mem-bership, and variability information, which is used to classify the SAGE-Spec sample of point sources. The decision tree has a broad application to mid-infrared spectroscopic surveys, where supporting photometry and variability information are available. We use these classifications to make deductions about the stellar populations of the Large Magellanic Cloud and the success of photometric classification methods. We find 90 asymptotic giant branch (AGB) stars, 29 young stellar objects, 23 post-AGB objects, 19 red supergiants, eight stellar photospheres, seven background galaxies, seven plane-tary nebulae, two Hii regions and 12 other objects, seven of which remain unclassified.
A. K. Speck Mon. Not. R. Astron. Soc. 01/2010; 15211813(000):2-34.
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J. M. Oliveira,
J. Th. van Loon, C.-H. R. Chen,
A. G. G. M. Tielens,
G. C. Sloan,
P. M. Woods,
F. Kemper,
R. Indebetouw,
K. D. Gordon,
M. L. Boyer,
B. Shiao,
S. Madden,
A. K. Speck,
M. Meixner,
and M. Marengo
[show abstract]
[hide abstract]
ABSTRACT: We present spectroscopic observations of a sample of 15 embedded young stellar objects (YSOs) in the Large Magellanic Cloud (LMC). These observations were obtained with the Spitzer Infrared Spectrograph (IRS) as part of the SAGE-Spec Legacy program. We analyze the two prominent ice bands in the IRS spectral range: the bending mode of CO2 ice at 15.2 μm and the ice band between 5 and 7 μm that includes contributions from the bending mode of water ice at 6 μm among other ice species. The 5-7 μm band is difficult to identify in our LMC sample due to the conspicuous presence of polycyclic aromatic hydrocarbon emission superimposed onto the ice spectra. We identify water ice in the spectra of two sources; the spectrum of one of those sources also exhibits the 6.8 μm ice feature attributed in the literature to ammonium and methanol. We model the CO2 band in detail, using the combination of laboratory ice profiles available in the literature. We find that a significant fraction (50%) of CO2 ice is locked in a water-rich component, consistent with what is observed for Galactic sources. The majority of the sources in the LMC also require a pure-CO2 contribution to the ice profile, evidence of thermal processing. There is a suggestion that CO2 production might be enhanced in the LMC, but the size of the available sample precludes firmer conclusions. We place our results in the context of the star formation environment in the LMC.
The Astrophysical Journal 12/2009; 707(2):1269. · 6.02 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: We have used Spitzer IRAC and MIPS observations of N44 to identify young stellar objects (YSOs). Sixty YSO candidates with masses 4M are identified. We have compared the distribution of YSOs with those of the ionized gas, molecular clouds, and HI gas to study the properties of star formation.
Proceedings of the International Astronomical Union 07/2006; 2:401 - 401.
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Y. -H. Chu,
R. A. Gruendl, C. -H. R. Chen,
B. A. Whitney,
K. D. Gordon,
L. W. Looney,
G. C. Clayton,
J. R. Dickel,
B. C. Dunne,
S. D. Points,
R. C. Smith,
R. M. Williams
[show abstract]
[hide abstract]
ABSTRACT: Using Spitzer Space Telescope and Hubble Space Telescope observations of the superbubble N51D, we have identified three young stellar objects (YSOs) in dust globules, and made the first detection of a Herbig-Haro object outside the Galaxy. The spectral energy distributions of these YSOs suggest young massive stars with disk, envelope, and outflow cavities. The interstellar conditions are used to assess whether the star formation was spontaneous or induced by external pressure. Comment: 12 pages, 4 figures, accepted for ApJL, December 1, 2005 High-resolution figures can be requested via e-mail to chu@astro.uiuc.edu. Replacement corrects author name
11/2005;
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[show abstract]
[hide abstract]
ABSTRACT: The giant HII region 30 Doradus is known for its violent internal motions and bright diffuse X-ray emission, suggesting the existence of supernova remnants (SNRs), but no nonthermal radio emission has been detected. Recently, Lazendic et al. compared the H-alpha/H-beta and radio/H-alpha ratios and suggested two small radio sources to be nonthermal and thus SNR candidates; however, no optical or X-ray counterparts were detected. We have used high-resolution optical images and high-dispersion spectra to examine the morphological, spectral, and kinematic properties of these two SNR candidates, and still find no optical evidence supporting their identification as SNRs. We have also determined the X-ray luminosities of these SNR candidates, and find them 1-3 orders of magnitude lower than those commonly seen in young SNRs. High extinction can obscure optical and X-ray signatures of an SNR, but would prohibit the use of a high radio/H-alpha ratio to identify nonthermal radio emission. We suggest that the SNR candidate MCRX J053831.8-690620 is associated with a young star forming region; while the radio emission originates from the obscured star forming region, the observed optical emission is dominated by the foreground. We suggest that the SNR candidate MCRX J053838.8-690730 is associated with a dust/molecular cloud, which obscures some optical emission but not the radio emission. Comment: 13 pages, 2 figures, accepted for publication in the ApJ, Nov 10, 2004
07/2004;
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[show abstract]
[hide abstract]
ABSTRACT: Superbubbles surrounding OB associations provide ideal laboratories to study the stellar energy feedback problem because the stellar energy input can be estimated from the observed stellar content of the OB associations and the interstellar thermal and kinetic energies of superbubbles are well-defined and easy to observe. We have used DEM L 192, also known as N 51D, to carry out a detailed case study of the energy budget in a superbubble, and we find that the expected amount of stellar mechanical energy injected into the ISM, (18+-5)x10^51 ergs, exceeds the amount of thermal and kinetic energies stored in the superbubble, (6+-2)x10^51 ergs. Clearly, a significant fraction of the stellar mechanical energy must have been converted to other forms of energy. The X-ray spectrum of the diffuse emission from DEM L 192 requires a power-law component to explain the featureless emission at 1.0-3.0 keV. The origin of this power-law component is unclear, but it may be responsible for the discrepancy between the stellar energy input and the observed interstellar energy in DEM L 192. Comment: 22 pages, 5 figures, 2 tables, to appear in the Astrophysical Journal, April 20 issue
01/2004;
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[show abstract]
[hide abstract]
ABSTRACT: We have analyzed Chandra archival observations of the Antennae galaxies to study the distribution and physical properties of its hot interstellar gas. Eleven distinct diffuse X-ray emission regions are selected according to their underlying interstellar structures and star formation activity. The X-ray spectra of these regions are used to determine their thermal energy contents and cooling timescales. Young star clusters in these regions are also identified and their photometric measurements are compared to evolutionary stellar population synthesis models to assess their masses and ages. The cluster properties are then used to determine the stellar wind and supernova energies injected into the ISM. Comparisons between the thermal energy in the hot ISM and the expected stellar energy input show that young star clusters are sufficient to power the X-ray-emitting gas in some, but not all, active star formation regions. Super-star clusters, with masses >= 1x10^5 M_sol, heat the ISM, but the yield of hot interstellar gas is not directly proportional to the cluster mass. Finally, there exist diffuse X-ray emission regions which do not show active star formation or massive young star clusters. These regions may be powered by field stars or low-mass clusters formed within the last ~100 Myr. Comment: 36 pages, 6 figures, 8 tables, 2 appendices, to appear in the Astrophysical Journal, April 20 issue
01/2004;
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[show abstract]
[hide abstract]
ABSTRACT: Narrow-band HST WFPC2 images reveal a bow-shock-like halo around the HII region N30B toward the B[e] supergiant Hen S22 located within the larger DEM L 106 nebula in the Large Magellanic Cloud. High-dispersion spectra of N30B show a narrow H-alpha emission component from the ionized gas; the velocity variations indicate a gas flow of -5 to -10 km/s in the vicinity of the HII regions, which is resultant from interactions with Hen S22's stellar wind and responsible for the bow-shock morphology. Spectra of N30B's halo show broad H-alpha profiles extending over >1000 km/s, similar to that of Hen S22, indicating that the halo is a reflection nebula of Hen S22. Broad-band morphologies of N30B's halo are also consistent with the reflection nebula interpretation. We use dust-scattering properties and the observed brightnesses of the reflection nebula and Hen S22 to constrain the reflection geometry. The reflected stellar H-alpha emission and absorption vary across the reflection nebula as a result of viewing S22's anisotropic wind across varying angles. This reflection nebula, together with the edge-on orientation of Hen S22's disk, provides an invaluable opportunity to study the disk and polar winds of a B[e] supergiant. Comment: 19 pages, 7 figures, Astronomical Journal, accepted for April 2003 issue
12/2002;
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[show abstract]
[hide abstract]
ABSTRACT: Two unusually energetic supernova remnants (SNRs) in M101, NGC 5471B and
MF83, have been suggested to be produced by hypernovae, possible
candidates for gamma ray bursts (Wang 1999, ApJL, in press). We have
obtained new HST WFPC2 images of NGC 5471B and new KPNO 4m echelle
spectra of NGC 5471B and MF83. We have also uncovered 13-yr old KPNO
2.1m CCD images of MF83. These data allow us to examine the stellar and
interstellar environments, and to determine the expansion velocities,
masses, and kinetic energies of these two remnants. Using these results
and Sedov's similarity solution for a point blast, we can further derive
the explosion energies, remnant ages, and ambient densities. These
results are critically examined to test the suggestion that they are
hypernova remnants.
04/1999; 31:907.
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[show abstract]
[hide abstract]
ABSTRACT: Bright X-ray emission has been detected in superbubbles in the Large
Magellanic Cloud (LMC). As their X-ray luminosities are much higher than
those expected in superbubble models by, e.g., Weaver et al. (1977), it
is suggested that supernova remnants (SNRs) hitting the inner shell
walls are responsible for the X-ray emission (Chu & Mac Low 1990).
To identify SNR shocks in superbubble interiors, we have obtained HST
WFPC2 images of the X-ray-bright superbubbles N44 and N51D in Hα
and [S II] lines, and the X-ray-dim superbubble DEM106 in Hα . We
expect to use the filamentary morphology and [S II]/Hα ratio to
identify SNR shocks. Of these three superbubbles, N44 has the highest
X-ray surface brightness. N44 also has the most filamentary nebular
morphology, the largest expansion velocity ( ~ 45 km/s), and the highest
[S II]/Hα ratio (0.4--0.6). The [S II]/Hα ratio increases
outwards and peaks in sharp filaments along the periphery. N51D has a
moderate X-ray surface brightness. N51D has a turbulent, but not
filamentary, morphology, a moderate expansion velocity (35 km/s), and a
low [S II]/Hα ratio ( ~ 0.15). DEM106 is not detected in X-rays.
Its shell structure is amorphous and has embedded dusty features. Its
expansion velocity is < 10 km/s. In order to determine whether the
morphological differences among N44, N51D, and DEM106 are statistically
significant, we have examined all archival WFPC2 Hα images of LMC
fields. We find a good correlation between X-ray surface brightness and
sharp filamentary nebular morphology, suggesting that SNR shocks are
responsible for the filamentary morphology. Therefore, high-resolution
imaging is an effective way to identify SNR shocks. The [S II]/Hα
ratio is not an effective indicator of SNR shocks near OB associations,
unless its spatial variation is taken into account.
04/1999; 31:948.
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Article:
The
S. Hony,
F. Galliano,
S. C. Madden,
P. Panuzzo,
M. Meixner,
C. Engelbracht,
K. Misselt,
M. Galametz,
M. Sauvage,
J. Roman-Duval, [......],
K Okumura, C. -H. R. Chen,
R. Indebetouw,
F. P. Israel,
E. Kwon,
A. Li,
F. Kemper,
M. S. Oey,
M. Rubio,
H. E. Triou
http://dx.doi.org/10.1051/0004-6361/201014628.
