The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Chris J Willott - One of the best experts on this subject based on the ideXlab platform.
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imaging of sdss z 6 quasar fields gravitational lensing companion galaxies and the host dark matter halos
The Astrophysical Journal, 2005Co-Authors: Chris J Willott, Will J Percival, R J Mclure, David Crampton, J B Hutchings, Matt J Jarvis, Marcin Sawicki, Luc SimardAbstract:We have undertaken deep optical imaging observations of three 6.2 < z < 6.5 quasar fields in the i' and z' filters. These data are used to search for foreground galaxies that are gravitationally lensing the quasars and distant galaxies physically associated with the quasars. Foreground galaxies are found closer than 5'' to the lines of sight of two of the three quasars. However, the Faintness of these galaxies suggests that they have fairly low masses and provide only weak magnifications (μ 1.1). No convincing galaxies physically associated with the quasars are found, and the number of i'-band dropouts is consistent with that found in random fields. We consider the expected dark matter halo masses that host these quasars under the assumption that a correlation between black hole mass and dark matter halo mass exists. We show that the steepness of the high-mass tail of the halo mass function at this redshift, combined with realistic amounts of scatter in this correlation, leads to expected halo masses substantially lower than previously believed. This analysis can explain the lack of companion galaxies found here and the low dynamical mass recently published for one of the quasars.
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imaging of sdss z 6 quasar fields gravitational lensing companion galaxies and the host dark matter halos
arXiv: Astrophysics, 2005Co-Authors: Chris J Willott, Will J Percival, R J Mclure, David Crampton, J B Hutchings, Matt J Jarvis, Marcin Sawicki, Luc SimardAbstract:We have undertaken deep optical imaging observations of three 6.2
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the Faintness of the 158 micron c ii transition in the z 6 42 quasar sdss j1148 5251
The Astrophysical Journal, 2004Co-Authors: Alberto D Bolatto, James Di Francesco, Chris J WillottAbstract:We report the nondetection of the [C II] (2P3/2 → 2P1/2) 157.74 μm transition in the z = 6.42 quasar SDSS J1148+5251 after 37.5 hr of integration with the James Clerk Maxwell Telescope. This transition is the main cooling line of the star-forming interstellar medium and usually the brightest far-infrared (FIR) line in galaxies. Our observed 1 σ rms = 1.3 mK in the T scale translates to L < 2.6 × 109 L☉. Using a recent estimate of the FIR continuum of this quasar, we derive for SDSS J1148+5251 L/LFIR < 5 × 10-4, a ratio similar to that observed in local ultraluminous infrared galaxies but considerably smaller than what is typical in nearby normal and starburst galaxies. This indicates that the small L/LFIR ratio observed locally in luminous FIR objects also persists at the highest redshifts.
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the Faintness of the 158 um cii transition in the z 6 42 quasar sdss j1148 5251
arXiv: Astrophysics, 2004Co-Authors: Alberto D Bolatto, James Di Francesco, Chris J WillottAbstract:We report the non-detection of the [CII] 157.74 um transition in the z=6.42 quasar SDSS J1148+5251 after 37.5 hours of integration with the James Clerk Maxwell Telescope. This transition is the main cooling line of the star-forming interstellar medium, and usually the brightest FIR line in galaxies. Our observed RMS of 1.3 mK in the Ta* scale translates to L([CII])<2.6 x 10^9 Lsun. Using a recent estimate of the far-infrared continuum of this quasar, we derive for SDSS J1148+5251 L([CII])/L(FIR)<5 x 10^-4, a ratio similar to that observed in local ultra-luminous infrared galaxies but considerably smaller than what is typical in nearby normal and starburst galaxies. This indicates that the small L([CII])/L(FIR) ratio observed locally in luminous far-infrared objects also persists at the highest redshifts.
Satoshi Yamamoto - One of the best experts on this subject based on the ideXlab platform.
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a recent accretion burst in the low mass protostar iras 15398 3359 alma imaging of its related chemistry
The Astrophysical Journal, 2013Co-Authors: J K Jorgensen, R Visser, Nami Sakai, Edwin A Bergin, C Brinch, Daniel Harsono, Johan E Lindberg, Ewine F Van Dishoeck, Satoshi YamamotoAbstract:Low-mass protostars have been suggested to show highly variable accretion rates throughout their evolution. Such changes in accretion, and related heating of their ambient envelopes, may trigger significant chemical variations on different spatial scales and from source-to-source. We present images of emission from C17O, H13CO+, CH3OH, C34S and C2H toward the low-mass protostar IRAS 15398-3359 on 0.''5 (75 AU diameter) scales with the Atacama Large Millimeter/submillimeter Array at 340 GHz. The resolved images show that the emission from H13CO+ is only present in a ring-like structure with a radius of about 1-1.''5 (150-200 AU) whereas the CO and other high dipole moment molecules are centrally condensed toward the location of the central protostar. We propose that HCO+ is destroyed by water vapor present on small scales. The origin of this water vapor is likely an accretion burst during the last 100-1000 yr increasing the luminosity of IRAS 15398-3359 by a factor of 100 above its current luminosity. Such a burst in luminosity can also explain the centrally condensed CH3OH and extended warm carbon-chain chemistry observed in this source and furthermore be reflected in the relative Faintness of its compact continuum emission compared to other protostars.
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a recent accretion burst in the low mass protostar iras 15398 3359 alma imaging of its related chemistry
arXiv: Solar and Stellar Astrophysics, 2013Co-Authors: J K Jorgensen, R Visser, Nami Sakai, Edwin A Bergin, C Brinch, Daniel Harsono, Johan E Lindberg, Ewine F Van Dishoeck, Satoshi YamamotoAbstract:Low-mass protostars have been suggested to show highly variable accretion rates through-out their evolution. Such changes in accretion, and related heating of their ambient envelopes, may trigger significant chemical variations on different spatial scales and from source-to-source. We present images of emission from C17O, H13CO+, CH3OH, C34S and C2H toward the low-mass protostar IRAS 15398-3359 on 0.5" (75 AU diameter) scales with the Atacama Large Millimeter/submillimeter Array (ALMA) at 340 GHz. The resolved images show that the emission from H13CO+ is only present in a ring-like structure with a radius of about 1-1.5" (150-200 AU) whereas the CO and other high dipole moment molecules are centrally condensed toward the location of the central protostar. We propose that HCO+ is destroyed by water vapor present on small scales. The origin of this water vapor is likely an accretion burst during the last 100-1000 years increasing the luminosity of IRAS 15398-3359 by a factor of 100 above its current luminosity. Such a burst in luminosity can also explain the centrally condensed CH3OH and extended warm carbon-chain chemistry observed in this source and furthermore be reflected in the relative Faintness of its compact continuum emission compared to other protostars.
Daniel Harsono - One of the best experts on this subject based on the ideXlab platform.
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a recent accretion burst in the low mass protostar iras 15398 3359 alma imaging of its related chemistry
The Astrophysical Journal, 2013Co-Authors: J K Jorgensen, R Visser, Nami Sakai, Edwin A Bergin, C Brinch, Daniel Harsono, Johan E Lindberg, Ewine F Van Dishoeck, Satoshi YamamotoAbstract:Low-mass protostars have been suggested to show highly variable accretion rates throughout their evolution. Such changes in accretion, and related heating of their ambient envelopes, may trigger significant chemical variations on different spatial scales and from source-to-source. We present images of emission from C17O, H13CO+, CH3OH, C34S and C2H toward the low-mass protostar IRAS 15398-3359 on 0.''5 (75 AU diameter) scales with the Atacama Large Millimeter/submillimeter Array at 340 GHz. The resolved images show that the emission from H13CO+ is only present in a ring-like structure with a radius of about 1-1.''5 (150-200 AU) whereas the CO and other high dipole moment molecules are centrally condensed toward the location of the central protostar. We propose that HCO+ is destroyed by water vapor present on small scales. The origin of this water vapor is likely an accretion burst during the last 100-1000 yr increasing the luminosity of IRAS 15398-3359 by a factor of 100 above its current luminosity. Such a burst in luminosity can also explain the centrally condensed CH3OH and extended warm carbon-chain chemistry observed in this source and furthermore be reflected in the relative Faintness of its compact continuum emission compared to other protostars.
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a recent accretion burst in the low mass protostar iras 15398 3359 alma imaging of its related chemistry
arXiv: Solar and Stellar Astrophysics, 2013Co-Authors: J K Jorgensen, R Visser, Nami Sakai, Edwin A Bergin, C Brinch, Daniel Harsono, Johan E Lindberg, Ewine F Van Dishoeck, Satoshi YamamotoAbstract:Low-mass protostars have been suggested to show highly variable accretion rates through-out their evolution. Such changes in accretion, and related heating of their ambient envelopes, may trigger significant chemical variations on different spatial scales and from source-to-source. We present images of emission from C17O, H13CO+, CH3OH, C34S and C2H toward the low-mass protostar IRAS 15398-3359 on 0.5" (75 AU diameter) scales with the Atacama Large Millimeter/submillimeter Array (ALMA) at 340 GHz. The resolved images show that the emission from H13CO+ is only present in a ring-like structure with a radius of about 1-1.5" (150-200 AU) whereas the CO and other high dipole moment molecules are centrally condensed toward the location of the central protostar. We propose that HCO+ is destroyed by water vapor present on small scales. The origin of this water vapor is likely an accretion burst during the last 100-1000 years increasing the luminosity of IRAS 15398-3359 by a factor of 100 above its current luminosity. Such a burst in luminosity can also explain the centrally condensed CH3OH and extended warm carbon-chain chemistry observed in this source and furthermore be reflected in the relative Faintness of its compact continuum emission compared to other protostars.
Luc Simard - One of the best experts on this subject based on the ideXlab platform.
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imaging of sdss z 6 quasar fields gravitational lensing companion galaxies and the host dark matter halos
The Astrophysical Journal, 2005Co-Authors: Chris J Willott, Will J Percival, R J Mclure, David Crampton, J B Hutchings, Matt J Jarvis, Marcin Sawicki, Luc SimardAbstract:We have undertaken deep optical imaging observations of three 6.2 < z < 6.5 quasar fields in the i' and z' filters. These data are used to search for foreground galaxies that are gravitationally lensing the quasars and distant galaxies physically associated with the quasars. Foreground galaxies are found closer than 5'' to the lines of sight of two of the three quasars. However, the Faintness of these galaxies suggests that they have fairly low masses and provide only weak magnifications (μ 1.1). No convincing galaxies physically associated with the quasars are found, and the number of i'-band dropouts is consistent with that found in random fields. We consider the expected dark matter halo masses that host these quasars under the assumption that a correlation between black hole mass and dark matter halo mass exists. We show that the steepness of the high-mass tail of the halo mass function at this redshift, combined with realistic amounts of scatter in this correlation, leads to expected halo masses substantially lower than previously believed. This analysis can explain the lack of companion galaxies found here and the low dynamical mass recently published for one of the quasars.
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imaging of sdss z 6 quasar fields gravitational lensing companion galaxies and the host dark matter halos
arXiv: Astrophysics, 2005Co-Authors: Chris J Willott, Will J Percival, R J Mclure, David Crampton, J B Hutchings, Matt J Jarvis, Marcin Sawicki, Luc SimardAbstract:We have undertaken deep optical imaging observations of three 6.2
J K Jorgensen - One of the best experts on this subject based on the ideXlab platform.
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a recent accretion burst in the low mass protostar iras 15398 3359 alma imaging of its related chemistry
The Astrophysical Journal, 2013Co-Authors: J K Jorgensen, R Visser, Nami Sakai, Edwin A Bergin, C Brinch, Daniel Harsono, Johan E Lindberg, Ewine F Van Dishoeck, Satoshi YamamotoAbstract:Low-mass protostars have been suggested to show highly variable accretion rates throughout their evolution. Such changes in accretion, and related heating of their ambient envelopes, may trigger significant chemical variations on different spatial scales and from source-to-source. We present images of emission from C17O, H13CO+, CH3OH, C34S and C2H toward the low-mass protostar IRAS 15398-3359 on 0.''5 (75 AU diameter) scales with the Atacama Large Millimeter/submillimeter Array at 340 GHz. The resolved images show that the emission from H13CO+ is only present in a ring-like structure with a radius of about 1-1.''5 (150-200 AU) whereas the CO and other high dipole moment molecules are centrally condensed toward the location of the central protostar. We propose that HCO+ is destroyed by water vapor present on small scales. The origin of this water vapor is likely an accretion burst during the last 100-1000 yr increasing the luminosity of IRAS 15398-3359 by a factor of 100 above its current luminosity. Such a burst in luminosity can also explain the centrally condensed CH3OH and extended warm carbon-chain chemistry observed in this source and furthermore be reflected in the relative Faintness of its compact continuum emission compared to other protostars.
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a recent accretion burst in the low mass protostar iras 15398 3359 alma imaging of its related chemistry
arXiv: Solar and Stellar Astrophysics, 2013Co-Authors: J K Jorgensen, R Visser, Nami Sakai, Edwin A Bergin, C Brinch, Daniel Harsono, Johan E Lindberg, Ewine F Van Dishoeck, Satoshi YamamotoAbstract:Low-mass protostars have been suggested to show highly variable accretion rates through-out their evolution. Such changes in accretion, and related heating of their ambient envelopes, may trigger significant chemical variations on different spatial scales and from source-to-source. We present images of emission from C17O, H13CO+, CH3OH, C34S and C2H toward the low-mass protostar IRAS 15398-3359 on 0.5" (75 AU diameter) scales with the Atacama Large Millimeter/submillimeter Array (ALMA) at 340 GHz. The resolved images show that the emission from H13CO+ is only present in a ring-like structure with a radius of about 1-1.5" (150-200 AU) whereas the CO and other high dipole moment molecules are centrally condensed toward the location of the central protostar. We propose that HCO+ is destroyed by water vapor present on small scales. The origin of this water vapor is likely an accretion burst during the last 100-1000 years increasing the luminosity of IRAS 15398-3359 by a factor of 100 above its current luminosity. Such a burst in luminosity can also explain the centrally condensed CH3OH and extended warm carbon-chain chemistry observed in this source and furthermore be reflected in the relative Faintness of its compact continuum emission compared to other protostars.
