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G Trinchieri - One of the best experts on this subject based on the ideXlab platform.
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chandra observations of the ulx n10 in the Cartwheel galaxy
Monthly Notices of the Royal Astronomical Society, 2010Co-Authors: Fabio Pizzolato, A Wolter, G TrinchieriAbstract:The Cartwheel galaxy harbours more ultraluminous X-ray sources (ULXs) than any other galaxy observed so far, and as such it is a particularly interesting target to study them. In this paper, we analyse the three Chandra observations of the brightest ULX (N 10) in the Cartwheel galaxy, in light of current theoretical models suggested to explain such still elusive objects. For each model, we derive the relevant spectral parameters. Based on self-consistency arguments, we can interpret N10 as an accreting binary system powered by an ∼100 M ⊙ black hole. A young supernova strongly interacting with its surroundings is a likely alternative that can be discarded only with the evidence of a flux increase from future observations.
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the Cartwheel galaxy with xmm newton
Astronomy and Astrophysics, 2009Co-Authors: E Crivellari, A Wolter, G TrinchieriAbstract:Aims. The extreme environment provided by the Cartwheel ring is analyzed to study its X-ray and optical-UV properties. We compare the Cartwheel with the other members of its group and study the system as a whole in the X-ray band. Methods. We analyze the data of the Cartwheel galaxy obtained with XMM-Newton in two different periods (December 2004 and May 2005). We focus on the X-ray properties of the system and use the OM data to obtain additional information in the optical and UV bands. Each dataset is analyzed separately to study source variability and summed together to study fainter and extended sources. Results. We detect a total of 8 sources associated with the Cartwheel galaxy and three in its vicinity, including G1 and G2, all at L X ≥ 10 39 erg s -1 , that is the Ultra Luminous X-ray (ULX) source range. The brightest ULX source has been already discussed elsewhere. The spectra of the next three brightest ULX are well fitted by a power-law model with a mean photon index of ~2. We compare the XMM-Newton and Chandra datasets to study the long-term variability of the sources. At least three sources vary in the 5 months between the two XMM-Newton observations and at least four in the 4-year timeframe between Chandra and XMM-Newton observations. One Chandra source disappears and a new one is detected by XMM-Newton in the ring. Optical-UV colors of the Cartwheel ring are consistent with a burst of star formation that is close to reaching its maximum, yielding a mean stellar age of about 40 Myr. The inferred variability and age suggest that high mass X-ray binaries are the counterparts to the ULX sources. The 3 companion galaxies have luminosities in the range 10 39-40 erg/s consistent with expectations. The hot gas of the Cartwheel galaxy is luminous and abundant (a few 10 8 ${M_{\odot}}$) and is found both in the outer ring, and in the inner part of the galaxy, behind the shock wave front. We also detect gas in the group with L X ~ 10 40 erg s -1 .
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the ulx population in the Cartwheel galaxy
A POPULATION EXPLOSION: The Nature & Evolution of X‐ray Binaries in Diverse#N#Environments, 2008Co-Authors: G Trinchieri, A Wolter, E CrivellariAbstract:The Cartwheel galaxy has revealed unexpected X‐ray features: a large number of Ultra Luminous X‐ray sources, including the brightest ever observed, a diffuse structure of hot gas in the outer ring, and low level diffuse emission inside the ring. A detailed analysis of the XMM‐Newton data combined with previous Chandra results allows us to study the diffuse component and the ULX sources, for which we can derive variability and luminosity properties. Optical, IR, and UV images will also allow us to study the environment in which ULX form and reside.
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variability of ultraluminous x ray sources in the Cartwheel ring
arXiv: Astrophysics, 2006Co-Authors: A Wolter, G Trinchieri, M ColpiAbstract:The Cartwheel is one of the most outstanding examples of a dynamically perturbed galaxy where star formation is occurring inside the ring–like structure. In previous studies with Chandra , we detected 16 Ultra Luminous X-ray sources lying along the southern portion of the ring. Their Luminosity Function is consistent with them being in the high luminosity tail of the High Mass X-ray Binaries distribution, but with one exception: source N.10. This source, detected with Chandra at L X = 1 × 10 41 erg s −1 , is among the brightest non–nuclear sources ever seen in external galaxies. Recently, we have observed the Cartwheel with XMM-Newton in two epochs, six months apart. After having been at its brightest for at least 4 years, the source has dimmed by at least a factor of two between the two observations. This fact implies that the source is compact in nature. Given its extreme isotropic luminosity, there is the possibility that the source hosts an accreting intermediate–mass black hole. Other sources in the ring vary in flux between the different datasets. We discuss our findings in the context of ULX models.
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the Cartwheel ring under x ray light
MSAIS, 2003Co-Authors: A Wolter, G TrinchieriAbstract:The Cartwheel, archetypical ring galaxy with strong star formation activity concentrated in a peculiar annular structure, has been imaged with the CHANDRA ACIS-S instrument. We present here preliminary results, that confirm the high luminosity detected earlier with the ROSAT HRI. Many bright isolated sources are visible in the star-forming ring. A diffuse component at luminosity of the order of 10 cgs is also detected.
Paul Guichard - One of the best experts on this subject based on the ideXlab platform.
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novel features of centriole polarity and Cartwheel stacking revealed by cryo tomography
bioRxiv, 2020Co-Authors: S Nazarov, Paul Guichard, A Bezler, Georgios N Hatzopoulos, Nemcikova V Villimova, Davide Demurtas, Le M Guennec, Pierre GonczyAbstract:Centrioles are polarized microtubule-based organelles that seed the formation of cilia, and which assemble from a Cartwheel containing stacked ring oligomers of SAS-6 proteins. A cryo-tomography map of centrioles from the termite flagellate Trichonympha spp. was obtained previously, but higher resolution analysis is likely to reveal novel features. Using sub-tomogram averaging (STA) in T. spp. and Trichonympha agilis, we delineate the architecture of centriolar microtubules, pinhead and A-C-linker. Moreover, we report [~]25 [A] resolution maps of the central Cartwheel, revealing notably polarized Cartwheel inner densities (CID). Furthermore, STA of centrioles from the distant flagellate Teranympha mirabilis uncovers similar Cartwheel architecture and a distinct filamentous CID. Fitting the CrSAS-6 crystal structure into the flagellate maps and analyzing Cartwheels generated in vitro indicates that SAS-6 rings can directly stack onto one another in two alternating configurations: with a slight rotational offset and in register. Overall, improved STA maps in three flagellates enabled us to unravel novel architectural features, including of centriole polarity and Cartwheel stacking, thus setting the stage for an accelerated elucidation of underlying assembly mechanisms.
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the rise of the Cartwheel seeding the centriole organelle
BioEssays, 2018Co-Authors: Paul Guichard, Virginie Hamel, Pierre GonczyAbstract:: The Cartwheel is a striking structure critical for building the centriole, a microtubule-based organelle fundamental for organizing centrosomes, cilia, and flagella. Over the last 50 years, the Cartwheel has been described in many systems using electron microscopy, but the molecular nature of its constituent building blocks and their assembly mechanisms have long remained mysterious. Here, we review discoveries that led to the current understanding of Cartwheel structure, assembly, and function. We focus on the key role of SAS-6 protein self-organization, both for building the signature ring-like structure with hub and spokes, as well as for their vertical stacking. The resemblance of assembly intermediates in vitro and in vivo leads us to propose a novel registration step in Cartwheel biogenesis, whereby stacked SAS-6-containing rings are put in register through interactions with peripheral elements anchored to microtubules. We conclude by evoking some avenues for further uncovering Cartwheel and centriole assembly mechanisms.
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cell free reconstitution reveals centriole Cartwheel assembly mechanisms
Nature Communications, 2017Co-Authors: Virginie Hamel, Paul Guichard, Le M Guennec, Niccolo Banterle, Ioan Iacovache, V Nemcikova, Isabelle Fluckiger, Kenneth N GoldieAbstract:How cellular organelles assemble is a fundamental question in biology. The centriole organelle organizes around a nine-fold symmetrical Cartwheel structure typically ∼100 nm high comprising a stack of rings that each accommodates nine homodimers of SAS-6 proteins. Whether nine-fold symmetrical ring-like assemblies of SAS-6 proteins harbour more peripheral Cartwheel elements is unclear. Furthermore, the mechanisms governing ring stacking are not known. Here we develop a cell-free reconstitution system for core Cartwheel assembly. Using cryo-electron tomography, we uncover that the Chlamydomonas reinhardtii proteins CrSAS-6 and Bld10p together drive assembly of the core Cartwheel. Moreover, we discover that CrSAS-6 possesses autonomous properties that ensure self-organized ring stacking. Mathematical fitting of reconstituted Cartwheel height distribution suggests a mechanism whereby preferential addition of pairs of SAS-6 rings governs Cartwheel growth. In conclusion, we have developed a cell-free reconstitution system that reveals fundamental assembly principles at the root of centriole biogenesis. The centriole is an organelle composed of rings of SAS-6 proteins that form a Cartwheel structure. Here the authors develop a cell-free system to examine core Cartwheel assembly ofC. reinhardtiiproteins and discover that CrSAS-6 has autonomous properties that facilitates self-organized stacking of pairs of rings.
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sas 6 engineering reveals interdependence between Cartwheel and microtubules in determining centriole architecture
Nature Cell Biology, 2016Co-Authors: Manuel Hilbert, Akira Noga, Daniel Frey, Virginie Hamel, Paul Guichard, Sebastian H W Kraatz, Moritz PfreundschuhAbstract:Centrioles are critical for the formation of centrosomes, cilia and flagella in eukaryotes. They are thought to assemble around a nine-fold symmetric Cartwheel structure established by SAS-6 proteins. Here, we have engineered Chlamydomonas reinhardtii SAS-6-based oligomers with symmetries ranging from five- to ten-fold. Expression of a SAS-6 mutant that forms six-fold symmetric Cartwheel structures in vitro resulted in Cartwheels and centrioles with eight- or nine-fold symmetries in vivo. In combination with Bld10 mutants that weaken Cartwheel-microtubule interactions, this SAS-6 mutant produced six- to eight-fold symmetric Cartwheels. Concurrently, the microtubule wall maintained eight- and nine-fold symmetries. Expressing SAS-6 with analogous mutations in human cells resulted in nine-fold symmetric centrioles that exhibited impaired length and organization. Together, our data suggest that the self-assembly properties of SAS-6 instruct Cartwheel symmetry, and lead us to propose a model in which the Cartwheel and the microtubule wall assemble in an interdependent manner to establish the native architecture of centrioles.
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Cartwheel architecture of trichonympha basal body
Science, 2012Co-Authors: Paul Guichard, Ambroise Desfosses, Aditi Maheshwari, Virginie Hachet, Carsten Dietrich, Andreas Brune, Takashi Ishikawa, Carsten Sachse, Pierre GonczyAbstract:Centrioles and basal bodies are essential for the formation of cilia, flagella, and centrosomes. They exhibit a characteristic ninefold symmetry imparted by a Cartwheel thought to contain rings of SAS-6 proteins. We used cryoelectron tomography to investigate the architecture of the exceptionally long Cartwheel of the flagellate Trichonympha . We found that the Cartwheel is a stack of central rings that exhibit a vertical periodicity of 8.5 nanometers and is able to accommodate nine SAS-6 homodimers. The spokes that emanate from two such rings associate into a layer, with a vertical periodicity of 17 nanometers on the Cartwheel margin. Thus, by using the power of biodiversity, we unveiled the architecture of the Cartwheel at the root of the ninefold symmetry of centrioles and basal bodies.
Virginie Hamel - One of the best experts on this subject based on the ideXlab platform.
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the rise of the Cartwheel seeding the centriole organelle
BioEssays, 2018Co-Authors: Paul Guichard, Virginie Hamel, Pierre GonczyAbstract:: The Cartwheel is a striking structure critical for building the centriole, a microtubule-based organelle fundamental for organizing centrosomes, cilia, and flagella. Over the last 50 years, the Cartwheel has been described in many systems using electron microscopy, but the molecular nature of its constituent building blocks and their assembly mechanisms have long remained mysterious. Here, we review discoveries that led to the current understanding of Cartwheel structure, assembly, and function. We focus on the key role of SAS-6 protein self-organization, both for building the signature ring-like structure with hub and spokes, as well as for their vertical stacking. The resemblance of assembly intermediates in vitro and in vivo leads us to propose a novel registration step in Cartwheel biogenesis, whereby stacked SAS-6-containing rings are put in register through interactions with peripheral elements anchored to microtubules. We conclude by evoking some avenues for further uncovering Cartwheel and centriole assembly mechanisms.
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cell free reconstitution reveals centriole Cartwheel assembly mechanisms
Nature Communications, 2017Co-Authors: Virginie Hamel, Paul Guichard, Le M Guennec, Niccolo Banterle, Ioan Iacovache, V Nemcikova, Isabelle Fluckiger, Kenneth N GoldieAbstract:How cellular organelles assemble is a fundamental question in biology. The centriole organelle organizes around a nine-fold symmetrical Cartwheel structure typically ∼100 nm high comprising a stack of rings that each accommodates nine homodimers of SAS-6 proteins. Whether nine-fold symmetrical ring-like assemblies of SAS-6 proteins harbour more peripheral Cartwheel elements is unclear. Furthermore, the mechanisms governing ring stacking are not known. Here we develop a cell-free reconstitution system for core Cartwheel assembly. Using cryo-electron tomography, we uncover that the Chlamydomonas reinhardtii proteins CrSAS-6 and Bld10p together drive assembly of the core Cartwheel. Moreover, we discover that CrSAS-6 possesses autonomous properties that ensure self-organized ring stacking. Mathematical fitting of reconstituted Cartwheel height distribution suggests a mechanism whereby preferential addition of pairs of SAS-6 rings governs Cartwheel growth. In conclusion, we have developed a cell-free reconstitution system that reveals fundamental assembly principles at the root of centriole biogenesis. The centriole is an organelle composed of rings of SAS-6 proteins that form a Cartwheel structure. Here the authors develop a cell-free system to examine core Cartwheel assembly ofC. reinhardtiiproteins and discover that CrSAS-6 has autonomous properties that facilitates self-organized stacking of pairs of rings.
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sas 6 engineering reveals interdependence between Cartwheel and microtubules in determining centriole architecture
Nature Cell Biology, 2016Co-Authors: Manuel Hilbert, Akira Noga, Daniel Frey, Virginie Hamel, Paul Guichard, Sebastian H W Kraatz, Moritz PfreundschuhAbstract:Centrioles are critical for the formation of centrosomes, cilia and flagella in eukaryotes. They are thought to assemble around a nine-fold symmetric Cartwheel structure established by SAS-6 proteins. Here, we have engineered Chlamydomonas reinhardtii SAS-6-based oligomers with symmetries ranging from five- to ten-fold. Expression of a SAS-6 mutant that forms six-fold symmetric Cartwheel structures in vitro resulted in Cartwheels and centrioles with eight- or nine-fold symmetries in vivo. In combination with Bld10 mutants that weaken Cartwheel-microtubule interactions, this SAS-6 mutant produced six- to eight-fold symmetric Cartwheels. Concurrently, the microtubule wall maintained eight- and nine-fold symmetries. Expressing SAS-6 with analogous mutations in human cells resulted in nine-fold symmetric centrioles that exhibited impaired length and organization. Together, our data suggest that the self-assembly properties of SAS-6 instruct Cartwheel symmetry, and lead us to propose a model in which the Cartwheel and the microtubule wall assemble in an interdependent manner to establish the native architecture of centrioles.
P N Appleton - One of the best experts on this subject based on the ideXlab platform.
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nonnuclear hyper ultraluminous x ray sources in the starbursting Cartwheel ring galaxy
The Astrophysical Journal, 2003Co-Authors: Daniel Q Wang, P N Appleton, R A LucasAbstract:We report the Chandra/ACIS-S detection of more than 20 ultraluminous X-ray sources (ULXs, L0.5−10keV > �3 × 10 39 ergss −1 ) in the Cartwheel collisional ring galaxy system, of which over a dozen are located in the outer active star-forming ring. A remarkable hyperluminous X-ray source (HLX, L0.5−10keV > �10 41 ergss −1 assuming isotropic radiation), which dominates the X-ray emission from the Cartwheel ring, is located in the same segment of the ring as most ULXs. These powerful H/ULXs appear to be coincident with giant HII region complexes, young star clusters, and radio and midinfrared hot-spots: all strong indicators of recent massive star formation. The X-ray spectra show that H/ULXs have similar properties as those of the most luminous ULXs found in the nearest starbursts and galaxy mergers such as the Antennae galaxies and M82. The close association between the X-ray sources and the starbursting ring strongly suggests that the H/ULXs are intimately associated with the production and rapid evolution of short-lived massive stars. The observations represent the most extreme X-ray luminosities discovered to date associated with star-forming regions—rivaling the X-ray luminosities usually associated with active galactic nuclei. Subject headings: galaxies: individual (VV 784, Cartwheel, ESO 350 G 040) — galaxies: interactions — galaxies: active — galaxies: starburst — X-rays: galaxies
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Nonnuclear Hyper/Ultraluminous X-Ray Sources in the Starbursting Cartwheel Ring Galaxy
The Astrophysical Journal, 2003Co-Authors: Q. Daniel Wang, P N Appleton, R A LucasAbstract:We report the Chandra/ACIS-S detection of more than 20 ultraluminous X-ray sources (ULXs, L0.5−10keV > �3 × 10 39 ergss −1 ) in the Cartwheel collisional ring galaxy system, of which over a dozen are located in the outer active star-forming ring. A remarkable hyperluminous X-ray source (HLX, L0.5−10keV > �10 41 ergss −1 assuming isotropic radiation), which dominates the X-ray emission from the Cartwheel ring, is located in the same segment of the ring as most ULXs. These powerful H/ULXs appear to be coincident with giant HII region complexes, young star clusters, and radio and midinfrared hot-spots: all strong indicators of recent massive star formation. The X-ray spectra show that H/ULXs have similar properties as those of the most luminous ULXs found in the nearest starbursts and galaxy mergers such as the Antennae galaxies and M82. The close association between the X-ray sources and the starbursting ring strongly suggests that the H/ULXs are intimately associated with the production and rapid evolution of short-lived massive stars. The observations represent the most extreme X-ray luminosities discovered to date associated with star-forming regions—rivaling the X-ray luminosities usually associated with active galactic nuclei. Subject headings: galaxies: individual (VV 784, Cartwheel, ESO 350 G 040) — galaxies: interactions — galaxies: active — galaxies: starburst — X-rays: galaxies
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dust in the wheel the Cartwheel galaxy in the mid ir
Astronomy and Astrophysics, 1999Co-Authors: V Charmandaris, I F Mirabel, O Laurent, P Gallais, M Sauvage, L Vigroux, C Cesarsky, P N AppletonAbstract:We present mid-infrared images at 6:7 m and 15 m of "The Cartwheel" (AM 0035-33), the prototypical col- lisional ring galaxy. The observations, taken with ISOCAM, reveal the distribution of hot dust in the galaxy and its two com- panions in the north-east. The intensity of the Mid-IR emission from the outer star forming ring of the Cartwheel shows con- siderable azimuthal variation and peaks at the most active H region of the ring. The 15 m to 6.7 m flux ratio of 5.2 is the highest among all the galaxies of our sample. A surprising result of our observations is the discovery of significant emission from the inner regions of the galaxy, including the inner ring, spokes and nucleus, where previously only low level H emission had been reported. At 6.7 m, this emission is stronger than the one from the outer star forming ring, and at 15 m, it represents 40% of the emission from the outer ring. The H to Mid-IR flux ratios from the inner regions are consistent with the heating of grains from weak star formation activity. ? Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, the Netherlands and the United Kingdom) with the partici- pation of ISAS and NASA.
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molecular gas in the Cartwheel galaxy
Astronomy and Astrophysics, 1998Co-Authors: C Horellou, P N Appleton, V Charmandaris, F Combes, F Casoli, I F MirabelAbstract:We present the first detection of molecular gas in the Cartwheel, the prototype of a collisional ring galaxy formed in the head-on encounter of two galaxies. Until now, only very little atomic gas and no CO had been detected in the centre, where gas is theoretically expected to pile up. Using the Swedish ESO Submm Telescope, we detected both 12 CO(1-0) and (2-1) line emission towards the central position. The line ratio and the line widths suggest that the CO(2-1) emission is sub-thermal and that the CO(1-0) emission arises within the central 22 00 (13 kpc); it is probably associated with the inner ring and nucleus. We infer a mass of molecular gas (H2) of 1.5 to 610 9 M, which is significantly higher than the 10 8 M of atomic gas within that region. The low excitation of the gas, whether it is due to a low temperature or a low density, is consistent with the weak star-forming activity observed in the centre of the Cartwheel.
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dust in the wheel the Cartwheel galaxy in the mid ir
arXiv: Astrophysics, 1998Co-Authors: V Charmandaris, I F Mirabel, O Laurent, P Gallais, M Sauvage, L Vigroux, C Cesarsky, P N AppletonAbstract:We present mid-infrared images at $6.7 \mu m$ and $15 \mu m$ of ``The Cartwheel'' (AM~0035-33), the prototypical collisional ring galaxy. The observations, taken with ISOCAM, reveal the distribution of hot dust in the galaxy and its two companions in the north-east. The intensity of the mid-IR emission from the outer star forming ring of the Cartwheel shows considerable azimuthal variation and peaks at the most active H$\alpha$ region of the ring. The 15 $\mu m$ to 6.7 $\mu m$ flux ratio of 5.2 is the highest among all the galaxies of our sample. A surprising result of our observations is the discovery of significant emission from the inner regions of the galaxy, including the inner ring, spokes and nucleus, where previously only low level H$\alpha$ emission had been reported. At 6.7 $\mu m$, this emission is stronger than the one from the outer star forming ring, and at 15 $\mu m$, it represents 40% of the emission from the outer ring. The H$\alpha$ to mid-IR flux ratios from the inner regions are consistent with the heating of grains from weak star formation activity.
A Wolter - One of the best experts on this subject based on the ideXlab platform.
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chandra observations of the ulx n10 in the Cartwheel galaxy
Monthly Notices of the Royal Astronomical Society, 2010Co-Authors: Fabio Pizzolato, A Wolter, G TrinchieriAbstract:The Cartwheel galaxy harbours more ultraluminous X-ray sources (ULXs) than any other galaxy observed so far, and as such it is a particularly interesting target to study them. In this paper, we analyse the three Chandra observations of the brightest ULX (N 10) in the Cartwheel galaxy, in light of current theoretical models suggested to explain such still elusive objects. For each model, we derive the relevant spectral parameters. Based on self-consistency arguments, we can interpret N10 as an accreting binary system powered by an ∼100 M ⊙ black hole. A young supernova strongly interacting with its surroundings is a likely alternative that can be discarded only with the evidence of a flux increase from future observations.
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the Cartwheel galaxy with xmm newton
Astronomy and Astrophysics, 2009Co-Authors: E Crivellari, A Wolter, G TrinchieriAbstract:Aims. The extreme environment provided by the Cartwheel ring is analyzed to study its X-ray and optical-UV properties. We compare the Cartwheel with the other members of its group and study the system as a whole in the X-ray band. Methods. We analyze the data of the Cartwheel galaxy obtained with XMM-Newton in two different periods (December 2004 and May 2005). We focus on the X-ray properties of the system and use the OM data to obtain additional information in the optical and UV bands. Each dataset is analyzed separately to study source variability and summed together to study fainter and extended sources. Results. We detect a total of 8 sources associated with the Cartwheel galaxy and three in its vicinity, including G1 and G2, all at L X ≥ 10 39 erg s -1 , that is the Ultra Luminous X-ray (ULX) source range. The brightest ULX source has been already discussed elsewhere. The spectra of the next three brightest ULX are well fitted by a power-law model with a mean photon index of ~2. We compare the XMM-Newton and Chandra datasets to study the long-term variability of the sources. At least three sources vary in the 5 months between the two XMM-Newton observations and at least four in the 4-year timeframe between Chandra and XMM-Newton observations. One Chandra source disappears and a new one is detected by XMM-Newton in the ring. Optical-UV colors of the Cartwheel ring are consistent with a burst of star formation that is close to reaching its maximum, yielding a mean stellar age of about 40 Myr. The inferred variability and age suggest that high mass X-ray binaries are the counterparts to the ULX sources. The 3 companion galaxies have luminosities in the range 10 39-40 erg/s consistent with expectations. The hot gas of the Cartwheel galaxy is luminous and abundant (a few 10 8 ${M_{\odot}}$) and is found both in the outer ring, and in the inner part of the galaxy, behind the shock wave front. We also detect gas in the group with L X ~ 10 40 erg s -1 .
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the ulx population in the Cartwheel galaxy
A POPULATION EXPLOSION: The Nature & Evolution of X‐ray Binaries in Diverse#N#Environments, 2008Co-Authors: G Trinchieri, A Wolter, E CrivellariAbstract:The Cartwheel galaxy has revealed unexpected X‐ray features: a large number of Ultra Luminous X‐ray sources, including the brightest ever observed, a diffuse structure of hot gas in the outer ring, and low level diffuse emission inside the ring. A detailed analysis of the XMM‐Newton data combined with previous Chandra results allows us to study the diffuse component and the ULX sources, for which we can derive variability and luminosity properties. Optical, IR, and UV images will also allow us to study the environment in which ULX form and reside.
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variability of ultraluminous x ray sources in the Cartwheel ring
arXiv: Astrophysics, 2006Co-Authors: A Wolter, G Trinchieri, M ColpiAbstract:The Cartwheel is one of the most outstanding examples of a dynamically perturbed galaxy where star formation is occurring inside the ring–like structure. In previous studies with Chandra , we detected 16 Ultra Luminous X-ray sources lying along the southern portion of the ring. Their Luminosity Function is consistent with them being in the high luminosity tail of the High Mass X-ray Binaries distribution, but with one exception: source N.10. This source, detected with Chandra at L X = 1 × 10 41 erg s −1 , is among the brightest non–nuclear sources ever seen in external galaxies. Recently, we have observed the Cartwheel with XMM-Newton in two epochs, six months apart. After having been at its brightest for at least 4 years, the source has dimmed by at least a factor of two between the two observations. This fact implies that the source is compact in nature. Given its extreme isotropic luminosity, there is the possibility that the source hosts an accreting intermediate–mass black hole. Other sources in the ring vary in flux between the different datasets. We discuss our findings in the context of ULX models.
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the Cartwheel ring under x ray light
MSAIS, 2003Co-Authors: A Wolter, G TrinchieriAbstract:The Cartwheel, archetypical ring galaxy with strong star formation activity concentrated in a peculiar annular structure, has been imaged with the CHANDRA ACIS-S instrument. We present here preliminary results, that confirm the high luminosity detected earlier with the ROSAT HRI. Many bright isolated sources are visible in the star-forming ring. A diffuse component at luminosity of the order of 10 cgs is also detected.