Gabriela Castelletti - Academia.edu (original) (raw)
Papers by Gabriela Castelletti
Radio observations X X--ray observations with XMM ray observations with XMM X X--ray mosaic image... more Radio observations X X--ray observations with XMM ray observations with XMM X X--ray mosaic images ray mosaic images Parameters of interest Parameters of interest Conclusions Conclusions Thermal and nonthermal electrons Thermal and nonthermal electrons Source regions and spectra Source regions and spectra SNRs and kinetics of electrons SNRs and kinetics of electrons VLA Parkes The best ever obtained radio image of SN1006 (synthesized beam 8''x5'') 2007 We make use of: -Brightness profiles -Fluxes for X-ray analysis -Detailed map for comparison with X-ray images SN1006 was oserved by XMM 8 times in period 2000-2005. Total cleaned exposure is 122 ksec EPIC MOS mosaic of SN1006 used for spectral analysis 0.5-0.8 keV 2.0-4.5 keV Exposure map observed modelled The goal is to estimate: electron thermalization level χ s, electron injection efficiency ς, energy partition between thermal and nonthermal electrons E nth /E th , -maximum energy of accelerated electrons E max their dependence on the shock velocity V and on the shock obliquity Observations yield: T es , n es , R, F ν , s, ν max Tes electron spectrum Level of electron thermalization Injection efficiency of electrons V V V arb.un. arb.un. V Two different methods are used for analysis of X-ray spectra the main difference is the way of background substraction Background regions (for ESAS analysis) are different for each observations
We have analyzed the vicinity of the supernova remnant (SNR) W44 looking for signatures of s... more We have analyzed the vicinity of the supernova remnant (SNR) W44 looking for signatures of star formation processes. A molecular cloud, an HII region, and three young stellar object candidates, overlap the SE edge of the remnant. We confirm that W44, the molecular cloud and the HII region are located at the same distance of ~ 2.9 kpc. We conclude that the star formation is likely to be in a primitive stage associated with the HII rather than with the SNR.
CTB 80 is a supernova remnant (SNR) which shows, in radio wavelengths, a complex morphology compo... more CTB 80 is a supernova remnant (SNR) which shows, in radio wavelengths, a complex morphology composed by three arms or extended regions and a central nebula formed by winds from the pulsar PSR B1951+32 physically associated with the remnant. New observations of the SNR CTB 80 have been carried out using the Giant Metrewave Radio Telescope (GMRT, Pune-India) at 240 MHz (beam ˜ 20'') and 618 MHz (beam ˜ 8''), and at 324 MHz (beam ˜ 65'') and 1380 MHz (beam ˜ 80'') using the Very Large Array (VLA, USA). These radio-images show with unprecedented detail new structures in the nebula powered by the pulsar. Likewise, the high dynamic range attained in the images allows us identify faint structures in the extended regions which closely match the optical and infrared emission.
Low frequencies observations in radio wavelengths are very useful to trace the energy distributio... more Low frequencies observations in radio wavelengths are very useful to trace the energy distribution of relativistic electrons emitting synchrotron radiation and can be used to anchor the low frequency end of the intrinsic radio spectra. Furthermore, detailed low frequencies measurements can help to distinguish between thermal and nonthermal components in complex regions and thus delineate the distribution of ionized gas in the interstellar medium (ISM). In this work we discuss different aspects of the data reduction procedures at very low frequencies based on new radio observations of the supernova remnant (SNR) W44 carried out at 74 MHz and 330 MHz using the A, B, C, and D configurations of the radio interferometer Very Large Array (VLA, USA).
We report on the detection of 12CO emission in the rotational transitions J=1-0 and 2-1 towards f... more We report on the detection of 12CO emission in the rotational transitions J=1-0 and 2-1 towards four selected regions along the eastern flank of the Puppis A SNR, where previous low resolution observations revealed the presence of an extended molecular cloud. The observations were carried out on March 2000 using the SEST telescope located in La Silla (Chile). The angular resolutions are 45" and 23" for both transitions respectively. From the analysis of these observations, it can be concluded that there are possibly associated molecular features at two different velocity ranges: vLSR˜+3 km/s and vLSR˜+16 km/s. The effects of the mutual interaction SNR/shocks are analyzed.
The bright supernova remnant W44 has been imaged at 74 and 330 MHz using the VLA at unprecedented... more The bright supernova remnant W44 has been imaged at 74 and 330 MHz using the VLA at unprecedented levels of angular resolution and sensitivity at these long wavelengths. Full three-dimensional wide field imaging techniques that take into account the non-coplanarity of the array at these low frequencies have been used to achieve high dynamic range images. Combining our new low frequency images with existing VLA data at 1.4 GHz, we investigate spectral index variations across the remnant. In particular, we utilize changes in the observed synchrotron radio spectrum near the pulsar PSR B1853+01, in the interior of W44, to that at the remnant's periphery, to explore differences in the energy spectra of the different particle populations. Previous X-ray observations of W44 carried out with Einstein, EXOSAT, ROSAT, and ASCA instruments have revealed that the X-ray emission is confined inside the radio continuum shell and is mostly thermal in origin. Recent Chandra studies have shown th...
In this paper we present multi-frequency radio observations of the supernova remnant (SNR) G338.3... more In this paper we present multi-frequency radio observations of the supernova remnant (SNR) G338.3-0.0. The data were acquired in 2008 with the Giant Metrewave Radio Telescope (GMRT, India) operating in dual mode 235/610 MHz and at 1280 MHz. The instrumental capabilities of GMRT permited to spatially resolve the emission down to few arcseconds. The new images represent a significant increase in resolution and sensitivity over previously published data.
We present new high quality images of the supernova remnant (SNR) Kes 79 (G33.6+0.1) at 74 and 32... more We present new high quality images of the supernova remnant (SNR) Kes 79 (G33.6+0.1) at 74 and 324 MHz. We also report a new radio continuum image of the SNR at 1.5 GHz obtained after reprocessing VLA archival data and combine them with single-dish observations. The new images reveal two incomplete concentric shells immersed in diffuse emission. Based on the new observations a cometary-like radio nebula with the pulsanting X-ray point source CXOU J185238.6+004020 located at the apex, has been detected at both 324 MHz and 1.5 GHz. A pulsar wind nebula origin is suggested for this structure.
The galactic supernova remnant (SNR) CTB 80 (G69.0+2.7) is a nonthermal radio source of unusual m... more The galactic supernova remnant (SNR) CTB 80 (G69.0+2.7) is a nonthermal radio source of unusual morphology. At radio frequencies the remnant presents a complex structure formed by three long arcs (about half a degree each) which extend to the north, east and southwest. It is one of the very few known SNR associated with a fast pulsar (PSR 1951+32) with a period of 40 ms which is interacting with the rest of the remnant forming a bright radio nebula around it. This compact region, ~30'' in diameter, is located on the western end of a plateau-like feature of size ~10' x 6', where the three wings intersect. At present there are not satisfactory explanations for the origin of this singular morphology. The present work report on radioastronomical observations of the SNR CTB 80 obtained at 330 and 1365 MHz with high angular resolution using the Very Large Array (VLA, NRAO) in its C and D configurations, respectively. This is the first study at low frequencies covering the ...
New high resolution and high sensitivity radio observations were conducted with the Giant Metrewa... more New high resolution and high sensitivity radio observations were conducted with the Giant Metrewave Radio Telescope (GMRT) in the direction of the gamma-ray source HESS J1640-465, in positional coincidence with the supernova remnant (SNR) G338.3-0.0. The new images, obtained at 235 MHz and at 610 MHz, allow us to confirm that G338.3-0.0 is a typical shell-like remnant. No sign of the existence of a pulsar wind nebula or a radio pulsar is detected in its interior. Whether the high-energy particles are accelerated at the SNR shell or associated with an undetected pulsar, is still an open question.
Se observ o el remanente de la SN 1006 a 1.4 GHz con alta resoluci on y sensibilidad. Estos datos... more Se observ o el remanente de la SN 1006 a 1.4 GHz con alta resoluci on y sensibilidad. Estos datos se combinaron con observaciones anteriores con el n de medir la expansi on de la c ascara. Se encontr o que el par ametro de expansi on , de nido como R / t , vale 0:62 para los l obulos brillantes. De acuerdo con modelos te oricos, estevalor signi car a que la materia expulsada est a interactuando con una distribuci on de densidad circunestelar que decrece como r 2, la cual se explica si hubo una p erdida de masa continua antes de la explosi on. Sin embargo, este podr a no ser el caso si SN 1006 a un se encuentra en la etapa evolutiva donde la masa estelar expulsada supera a la masa interestelar barrida.
The Astrophysical Journal, 2015
Monthly Notices of the Royal Astronomical Society
A number of important processes taking place around strong shocks in supernova remnants (SNRs) de... more A number of important processes taking place around strong shocks in supernova remnants (SNRs) depend on the shock obliquity. The measured synchrotron flux is a function of the aspect angle between interstellar magnetic field (ISMF) and the line of sight. Thus a model of non-thermal emission from SNRs should account for the orientation of the ambient magnetic field. We develop a new method for the estimation of the aspect angle, based on the comparison between observed and synthesized radio maps of SNRs, making different assumptions about the dependence of electron injection efficiency on the shock obliquity. The method uses the azimuthal profile of radio surface brightness as a probe for orientation of ambient magnetic field because it is almost insensitive to the downstream distribution of magnetic field and emitting electrons. We apply our method to a new radio image of SN 1006 produced on the basis of archival VLA and Parkes data. The image recovers emission from all spatial str...
The Journal of Chemical Physics
This paper presents a modified grand canonical ensemble which provides a new simple and efficient... more This paper presents a modified grand canonical ensemble which provides a new simple and efficient scheme to study few-body fluid-like inhomogeneous systems under confinement. The new formalism is implemented to investigate the exact thermodynamic properties of a hard sphere (HS) fluid-like system with up to three particles confined in a spherical cavity. In addition, the partition function of this system was used to analyze the surface thermodynamic properties of the many-HS system and to derive the exact curvature dependence of both the surface tension and adsorption in powers of the density. The expressions for the surface tension and the adsorption were also obtained for the many-HS system outside of a fixed hard spherical object. We used these results to derive the dependence of the fluid-substrate Tolman length up to first order in density.
The Astronomical Journal
We report new high-resolution and high-sensitivity radio observations of the extended supernova r... more We report new high-resolution and high-sensitivity radio observations of the extended supernova remnant (SNR) CTB 80 (G69.0+2.7) at 240, 324, 618, and 1380 MHz. The imaging of CTB 80 at 240 and 618 MHz was performed using the Giant Metrewave Radio Telescope in India. The observations at 324 and 1380 MHz were obtained using the Very Large Array of the National Radio Astronomy Observatory in its C and D configurations. The new radio images reveal faint extensions for the asymmetric arms of CTB 80. The arms are irregular, with filaments and clumps of size 1' (or 0.6 pc at a distance of 2 kpc). The radio image at 1380 MHz is compared with IR and optical emission. The IR-radio correspondence is excellent along the north arm of CTB 80. Ionized gas observed in the [S II] line perfectly matches the west and north edges of CTB 80. The central nebula associated with the pulsar PSR B1951+32 was investigated with an angular resolution of 10'' × 6''. The new radio image obtai...
RCW 103 is a shell type supernova remnant (SNR) that, according to near infrared observations, is... more RCW 103 is a shell type supernova remnant (SNR) that, according to near infrared observations, is interacting with a molecular cloud, specially to the south. In this paper we report on the study of the interstellar medium in an extended region towards RCW 103 based on HI 21 cm data acquired with the ATCA radiotelescope. Also, we report on the
Observations of the supernova remnants (SNRs) at meter and longer wavelengths are powerful tools ... more Observations of the supernova remnants (SNRs) at meter and longer wavelengths are powerful tools to differentiate physical processes taking place either in the SNRs (e.g. shock acceleration) or in the interstellar medium intervening along the line of sight towards them (e.g. thermal absorption). Kes 79 (G33.6+0.1) is a Galactic SNR rich in spatial structures in both, radio and X-ray bands,
Radio observations X X--ray observations with XMM ray observations with XMM X X--ray mosaic image... more Radio observations X X--ray observations with XMM ray observations with XMM X X--ray mosaic images ray mosaic images Parameters of interest Parameters of interest Conclusions Conclusions Thermal and nonthermal electrons Thermal and nonthermal electrons Source regions and spectra Source regions and spectra SNRs and kinetics of electrons SNRs and kinetics of electrons VLA Parkes The best ever obtained radio image of SN1006 (synthesized beam 8''x5'') 2007 We make use of: -Brightness profiles -Fluxes for X-ray analysis -Detailed map for comparison with X-ray images SN1006 was oserved by XMM 8 times in period 2000-2005. Total cleaned exposure is 122 ksec EPIC MOS mosaic of SN1006 used for spectral analysis 0.5-0.8 keV 2.0-4.5 keV Exposure map observed modelled The goal is to estimate: electron thermalization level χ s, electron injection efficiency ς, energy partition between thermal and nonthermal electrons E nth /E th , -maximum energy of accelerated electrons E max their dependence on the shock velocity V and on the shock obliquity Observations yield: T es , n es , R, F ν , s, ν max Tes electron spectrum Level of electron thermalization Injection efficiency of electrons V V V arb.un. arb.un. V Two different methods are used for analysis of X-ray spectra the main difference is the way of background substraction Background regions (for ESAS analysis) are different for each observations
We have analyzed the vicinity of the supernova remnant (SNR) W44 looking for signatures of s... more We have analyzed the vicinity of the supernova remnant (SNR) W44 looking for signatures of star formation processes. A molecular cloud, an HII region, and three young stellar object candidates, overlap the SE edge of the remnant. We confirm that W44, the molecular cloud and the HII region are located at the same distance of ~ 2.9 kpc. We conclude that the star formation is likely to be in a primitive stage associated with the HII rather than with the SNR.
CTB 80 is a supernova remnant (SNR) which shows, in radio wavelengths, a complex morphology compo... more CTB 80 is a supernova remnant (SNR) which shows, in radio wavelengths, a complex morphology composed by three arms or extended regions and a central nebula formed by winds from the pulsar PSR B1951+32 physically associated with the remnant. New observations of the SNR CTB 80 have been carried out using the Giant Metrewave Radio Telescope (GMRT, Pune-India) at 240 MHz (beam ˜ 20'') and 618 MHz (beam ˜ 8''), and at 324 MHz (beam ˜ 65'') and 1380 MHz (beam ˜ 80'') using the Very Large Array (VLA, USA). These radio-images show with unprecedented detail new structures in the nebula powered by the pulsar. Likewise, the high dynamic range attained in the images allows us identify faint structures in the extended regions which closely match the optical and infrared emission.
Low frequencies observations in radio wavelengths are very useful to trace the energy distributio... more Low frequencies observations in radio wavelengths are very useful to trace the energy distribution of relativistic electrons emitting synchrotron radiation and can be used to anchor the low frequency end of the intrinsic radio spectra. Furthermore, detailed low frequencies measurements can help to distinguish between thermal and nonthermal components in complex regions and thus delineate the distribution of ionized gas in the interstellar medium (ISM). In this work we discuss different aspects of the data reduction procedures at very low frequencies based on new radio observations of the supernova remnant (SNR) W44 carried out at 74 MHz and 330 MHz using the A, B, C, and D configurations of the radio interferometer Very Large Array (VLA, USA).
We report on the detection of 12CO emission in the rotational transitions J=1-0 and 2-1 towards f... more We report on the detection of 12CO emission in the rotational transitions J=1-0 and 2-1 towards four selected regions along the eastern flank of the Puppis A SNR, where previous low resolution observations revealed the presence of an extended molecular cloud. The observations were carried out on March 2000 using the SEST telescope located in La Silla (Chile). The angular resolutions are 45" and 23" for both transitions respectively. From the analysis of these observations, it can be concluded that there are possibly associated molecular features at two different velocity ranges: vLSR˜+3 km/s and vLSR˜+16 km/s. The effects of the mutual interaction SNR/shocks are analyzed.
The bright supernova remnant W44 has been imaged at 74 and 330 MHz using the VLA at unprecedented... more The bright supernova remnant W44 has been imaged at 74 and 330 MHz using the VLA at unprecedented levels of angular resolution and sensitivity at these long wavelengths. Full three-dimensional wide field imaging techniques that take into account the non-coplanarity of the array at these low frequencies have been used to achieve high dynamic range images. Combining our new low frequency images with existing VLA data at 1.4 GHz, we investigate spectral index variations across the remnant. In particular, we utilize changes in the observed synchrotron radio spectrum near the pulsar PSR B1853+01, in the interior of W44, to that at the remnant's periphery, to explore differences in the energy spectra of the different particle populations. Previous X-ray observations of W44 carried out with Einstein, EXOSAT, ROSAT, and ASCA instruments have revealed that the X-ray emission is confined inside the radio continuum shell and is mostly thermal in origin. Recent Chandra studies have shown th...
In this paper we present multi-frequency radio observations of the supernova remnant (SNR) G338.3... more In this paper we present multi-frequency radio observations of the supernova remnant (SNR) G338.3-0.0. The data were acquired in 2008 with the Giant Metrewave Radio Telescope (GMRT, India) operating in dual mode 235/610 MHz and at 1280 MHz. The instrumental capabilities of GMRT permited to spatially resolve the emission down to few arcseconds. The new images represent a significant increase in resolution and sensitivity over previously published data.
We present new high quality images of the supernova remnant (SNR) Kes 79 (G33.6+0.1) at 74 and 32... more We present new high quality images of the supernova remnant (SNR) Kes 79 (G33.6+0.1) at 74 and 324 MHz. We also report a new radio continuum image of the SNR at 1.5 GHz obtained after reprocessing VLA archival data and combine them with single-dish observations. The new images reveal two incomplete concentric shells immersed in diffuse emission. Based on the new observations a cometary-like radio nebula with the pulsanting X-ray point source CXOU J185238.6+004020 located at the apex, has been detected at both 324 MHz and 1.5 GHz. A pulsar wind nebula origin is suggested for this structure.
The galactic supernova remnant (SNR) CTB 80 (G69.0+2.7) is a nonthermal radio source of unusual m... more The galactic supernova remnant (SNR) CTB 80 (G69.0+2.7) is a nonthermal radio source of unusual morphology. At radio frequencies the remnant presents a complex structure formed by three long arcs (about half a degree each) which extend to the north, east and southwest. It is one of the very few known SNR associated with a fast pulsar (PSR 1951+32) with a period of 40 ms which is interacting with the rest of the remnant forming a bright radio nebula around it. This compact region, ~30'' in diameter, is located on the western end of a plateau-like feature of size ~10' x 6', where the three wings intersect. At present there are not satisfactory explanations for the origin of this singular morphology. The present work report on radioastronomical observations of the SNR CTB 80 obtained at 330 and 1365 MHz with high angular resolution using the Very Large Array (VLA, NRAO) in its C and D configurations, respectively. This is the first study at low frequencies covering the ...
New high resolution and high sensitivity radio observations were conducted with the Giant Metrewa... more New high resolution and high sensitivity radio observations were conducted with the Giant Metrewave Radio Telescope (GMRT) in the direction of the gamma-ray source HESS J1640-465, in positional coincidence with the supernova remnant (SNR) G338.3-0.0. The new images, obtained at 235 MHz and at 610 MHz, allow us to confirm that G338.3-0.0 is a typical shell-like remnant. No sign of the existence of a pulsar wind nebula or a radio pulsar is detected in its interior. Whether the high-energy particles are accelerated at the SNR shell or associated with an undetected pulsar, is still an open question.
Se observ o el remanente de la SN 1006 a 1.4 GHz con alta resoluci on y sensibilidad. Estos datos... more Se observ o el remanente de la SN 1006 a 1.4 GHz con alta resoluci on y sensibilidad. Estos datos se combinaron con observaciones anteriores con el n de medir la expansi on de la c ascara. Se encontr o que el par ametro de expansi on , de nido como R / t , vale 0:62 para los l obulos brillantes. De acuerdo con modelos te oricos, estevalor signi car a que la materia expulsada est a interactuando con una distribuci on de densidad circunestelar que decrece como r 2, la cual se explica si hubo una p erdida de masa continua antes de la explosi on. Sin embargo, este podr a no ser el caso si SN 1006 a un se encuentra en la etapa evolutiva donde la masa estelar expulsada supera a la masa interestelar barrida.
The Astrophysical Journal, 2015
Monthly Notices of the Royal Astronomical Society
A number of important processes taking place around strong shocks in supernova remnants (SNRs) de... more A number of important processes taking place around strong shocks in supernova remnants (SNRs) depend on the shock obliquity. The measured synchrotron flux is a function of the aspect angle between interstellar magnetic field (ISMF) and the line of sight. Thus a model of non-thermal emission from SNRs should account for the orientation of the ambient magnetic field. We develop a new method for the estimation of the aspect angle, based on the comparison between observed and synthesized radio maps of SNRs, making different assumptions about the dependence of electron injection efficiency on the shock obliquity. The method uses the azimuthal profile of radio surface brightness as a probe for orientation of ambient magnetic field because it is almost insensitive to the downstream distribution of magnetic field and emitting electrons. We apply our method to a new radio image of SN 1006 produced on the basis of archival VLA and Parkes data. The image recovers emission from all spatial str...
The Journal of Chemical Physics
This paper presents a modified grand canonical ensemble which provides a new simple and efficient... more This paper presents a modified grand canonical ensemble which provides a new simple and efficient scheme to study few-body fluid-like inhomogeneous systems under confinement. The new formalism is implemented to investigate the exact thermodynamic properties of a hard sphere (HS) fluid-like system with up to three particles confined in a spherical cavity. In addition, the partition function of this system was used to analyze the surface thermodynamic properties of the many-HS system and to derive the exact curvature dependence of both the surface tension and adsorption in powers of the density. The expressions for the surface tension and the adsorption were also obtained for the many-HS system outside of a fixed hard spherical object. We used these results to derive the dependence of the fluid-substrate Tolman length up to first order in density.
The Astronomical Journal
We report new high-resolution and high-sensitivity radio observations of the extended supernova r... more We report new high-resolution and high-sensitivity radio observations of the extended supernova remnant (SNR) CTB 80 (G69.0+2.7) at 240, 324, 618, and 1380 MHz. The imaging of CTB 80 at 240 and 618 MHz was performed using the Giant Metrewave Radio Telescope in India. The observations at 324 and 1380 MHz were obtained using the Very Large Array of the National Radio Astronomy Observatory in its C and D configurations. The new radio images reveal faint extensions for the asymmetric arms of CTB 80. The arms are irregular, with filaments and clumps of size 1' (or 0.6 pc at a distance of 2 kpc). The radio image at 1380 MHz is compared with IR and optical emission. The IR-radio correspondence is excellent along the north arm of CTB 80. Ionized gas observed in the [S II] line perfectly matches the west and north edges of CTB 80. The central nebula associated with the pulsar PSR B1951+32 was investigated with an angular resolution of 10'' × 6''. The new radio image obtai...
RCW 103 is a shell type supernova remnant (SNR) that, according to near infrared observations, is... more RCW 103 is a shell type supernova remnant (SNR) that, according to near infrared observations, is interacting with a molecular cloud, specially to the south. In this paper we report on the study of the interstellar medium in an extended region towards RCW 103 based on HI 21 cm data acquired with the ATCA radiotelescope. Also, we report on the
Observations of the supernova remnants (SNRs) at meter and longer wavelengths are powerful tools ... more Observations of the supernova remnants (SNRs) at meter and longer wavelengths are powerful tools to differentiate physical processes taking place either in the SNRs (e.g. shock acceleration) or in the interstellar medium intervening along the line of sight towards them (e.g. thermal absorption). Kes 79 (G33.6+0.1) is a Galactic SNR rich in spatial structures in both, radio and X-ray bands,