The Experts below are selected from a list of 221610 Experts worldwide ranked by ideXlab platform
Nick Scoville - One of the best experts on this subject based on the ideXlab platform.
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star formation history of a young super star cluster in ngc 4038 39 direct detection of low mass pre main sequence stars
The Astrophysical Journal, 2010Co-Authors: J Greissl, Michael Meyer, M H Christopher, Nick ScovilleAbstract:We present an analysis of the Near-Infrared Spectrum of a young massive star cluster in the overlap region of the interacting galaxies NGC 4038/39 using population synthesis models. Our goal is to model the cluster population as well as provide rough constraints on its initial mass function (IMF). The cluster shows signs of youth, such as thermal radio emission and strong hydrogen emission lines in the Near-Infrared. Late-type absorption lines are also present which are indicative of late-type stars in the cluster. The strength and ratio of these absorption lines cannot be reproduced through either late-type pre-main sequence (PMS) stars or red supergiants alone. Thus, we interpret the Spectrum as a superposition of two star clusters of different ages, which is feasible since the 1" Spectrum encompasses a physical region of ≈90 pc and radii of super-star clusters (SSCs) are generally measured to be a few parsecs. One cluster is young (≤ 3 Myr) and is responsible for part of the late-type absorption features, which are due to PMS stars in the cluster, and the hydrogen emission lines. The second cluster is older (6 Myr-18 Myr) and is needed to reproduce the overall depth of the late-type absorption features in the Spectrum. Both are required to accurately reproduce the Near-Infrared Spectrum of the object. Thus, we have directly detected PMS objects in an unresolved SSC for the first time using a combination of population synthesis models and PMS tracks. This analysis serves as a testbed of our technique to constrain the low-mass IMF in young SSCs as well as an exploration of the star formation history of young UC H II regions.
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star formation history of a young super star cluster in ngc 4038 39 direct detection of low mass pre main sequence stars
arXiv: Cosmology and Nongalactic Astrophysics, 2010Co-Authors: J Greissl, Michael Meyer, M H Christopher, Nick ScovilleAbstract:We present an analysis of the Near-Infrared Spectrum of a young massive star cluster in the overlap region of the interacting galaxies NGC 4038/39 using population synthesis models. Our goal is to model the cluster population as well as provide rough constraints on its initial mass function (IMF). The cluster shows signs of youth such as thermal radio emission and strong hydrogen emission lines in the Near-Infrared. Late-type absorption lines are also present which are indicative of late-type stars in the cluster. The strength and ratio of these absorption lines cannot be reproduced through either late-type pre-main sequence (PMS) stars or red supergiants alone. Thus we interpret the Spectrum as a superposition of two star clusters of different ages, which is feasible since the 1" Spectrum encompasses a physical region of ~90 pc and radii of super-star clusters are generally measured to be a few parsecs. One cluster is young (<= 3 Myr) and is responsible for part of the late-type absorption features, which are due to PMS stars in the cluster, and the hydrogen emission lines. The second cluster is older (6 Myr - 18 Myr) and is needed to reproduce the overall depth of the late-type absorption features in the Spectrum. Both are required to accurately reproduce the Near-Infrared Spectrum of the object. Thus we have directly detected PMS objects in an unresolved super-star cluster for the first time using a combination of population synthesis models and pre-main sequence tracks. This analysis serves as a testbed of our technique to constrain the low-mass IMF in young super-star clusters as well as an exploration of the star formation history of young UC HII regions.
Michael Meyer - One of the best experts on this subject based on the ideXlab platform.
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star formation history of a young super star cluster in ngc 4038 39 direct detection of low mass pre main sequence stars
The Astrophysical Journal, 2010Co-Authors: J Greissl, Michael Meyer, M H Christopher, Nick ScovilleAbstract:We present an analysis of the Near-Infrared Spectrum of a young massive star cluster in the overlap region of the interacting galaxies NGC 4038/39 using population synthesis models. Our goal is to model the cluster population as well as provide rough constraints on its initial mass function (IMF). The cluster shows signs of youth, such as thermal radio emission and strong hydrogen emission lines in the Near-Infrared. Late-type absorption lines are also present which are indicative of late-type stars in the cluster. The strength and ratio of these absorption lines cannot be reproduced through either late-type pre-main sequence (PMS) stars or red supergiants alone. Thus, we interpret the Spectrum as a superposition of two star clusters of different ages, which is feasible since the 1" Spectrum encompasses a physical region of ≈90 pc and radii of super-star clusters (SSCs) are generally measured to be a few parsecs. One cluster is young (≤ 3 Myr) and is responsible for part of the late-type absorption features, which are due to PMS stars in the cluster, and the hydrogen emission lines. The second cluster is older (6 Myr-18 Myr) and is needed to reproduce the overall depth of the late-type absorption features in the Spectrum. Both are required to accurately reproduce the Near-Infrared Spectrum of the object. Thus, we have directly detected PMS objects in an unresolved SSC for the first time using a combination of population synthesis models and PMS tracks. This analysis serves as a testbed of our technique to constrain the low-mass IMF in young SSCs as well as an exploration of the star formation history of young UC H II regions.
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star formation history of a young super star cluster in ngc 4038 39 direct detection of low mass pre main sequence stars
arXiv: Cosmology and Nongalactic Astrophysics, 2010Co-Authors: J Greissl, Michael Meyer, M H Christopher, Nick ScovilleAbstract:We present an analysis of the Near-Infrared Spectrum of a young massive star cluster in the overlap region of the interacting galaxies NGC 4038/39 using population synthesis models. Our goal is to model the cluster population as well as provide rough constraints on its initial mass function (IMF). The cluster shows signs of youth such as thermal radio emission and strong hydrogen emission lines in the Near-Infrared. Late-type absorption lines are also present which are indicative of late-type stars in the cluster. The strength and ratio of these absorption lines cannot be reproduced through either late-type pre-main sequence (PMS) stars or red supergiants alone. Thus we interpret the Spectrum as a superposition of two star clusters of different ages, which is feasible since the 1" Spectrum encompasses a physical region of ~90 pc and radii of super-star clusters are generally measured to be a few parsecs. One cluster is young (<= 3 Myr) and is responsible for part of the late-type absorption features, which are due to PMS stars in the cluster, and the hydrogen emission lines. The second cluster is older (6 Myr - 18 Myr) and is needed to reproduce the overall depth of the late-type absorption features in the Spectrum. Both are required to accurately reproduce the Near-Infrared Spectrum of the object. Thus we have directly detected PMS objects in an unresolved super-star cluster for the first time using a combination of population synthesis models and pre-main sequence tracks. This analysis serves as a testbed of our technique to constrain the low-mass IMF in young super-star clusters as well as an exploration of the star formation history of young UC HII regions.
Philip St J Russell - One of the best experts on this subject based on the ideXlab platform.
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carrier envelope phase stable soliton based pulse compression to 4 4 fs and ultraviolet generation at the 800 khz repetition rate
Optics Letters, 2019Co-Authors: Alexey Ermolov, Christian Heide, Philip Dienstbier, Felix Kottig, Francesco Tani, Peter Hommelhoff, Philip St J RussellAbstract:In this Letter, we report the generation of a femtosecond supercontinuum extending from the ultraviolet to the Near-Infrared Spectrum and detection of its carrier-envelope-phase (CEP) variation by f-to-2f interferometry. The Spectrum is generated in a gas-filled hollow-core photonic crystal fiber, where soliton dynamics allows the CEP-stable self-compression of the optical parametric chirped-pulse amplifier pump pulses at 800 nm to a duration of 1.7 optical cycles, followed by dispersive wave emission. The source provides up to 1 μJ of pulse energy at the 800 kHz repetition rate, resulting in 0.8 W of average power, and it can be extremely useful, for example in strong-field physics, pump–probe measurements, and ultraviolet frequency comb metrology.
Lynne A Hillenbrand - One of the best experts on this subject based on the ideXlab platform.
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the young substellar companion roxs 12 b near infrared Spectrum system architecture and spin orbit misalignment
The Astronomical Journal, 2017Co-Authors: Brendan P Bowler, Gregory N Mace, Adam L Kraus, Marta L Bryan, Heather A Knutson, Matteo Brogi, Aaron C Rizzuto, Andrew Vanderburg, Michael C Liu, Lynne A HillenbrandAbstract:ROXs 12 (2MASS J16262803–2526477) is a young star hosting a directly imaged companion near the deuterium-burning limit. We present a suite of spectroscopic, imaging, and time-series observations to characterize the physical and environmental properties of this system. Moderate-resolution Near-Infrared spectroscopy of ROXs 12 B from Gemini-North/NIFS and Keck/OSIRIS reveals signatures of low surface gravity including weak alkali absorption lines and a triangular H-band pseudocontinuum shape. No signs of Paβ emission are evident. As a population, however, we find that about half (46% ± 14%) of young (≾15 Myr) companions with masses ≾20 M_(Jup) possess actively accreting subdisks detected via Paβ line emission, which represents a lower limit on the prevalence of circumplanetary disks in general, as some are expected to be in a quiescent phase of accretion. The bolometric luminosity of the companion and age of the host star (6^(+4)_(-2) Myr) imply a mass of 17.5 ± 1.5 M_(Jup) for ROXs 12 B based on hot-start evolutionary models. We identify a wide (5100 au) tertiary companion to this system, 2MASS J16262774–2527247, that is heavily accreting and exhibits stochastic variability in its K2 light curve. By combining v sin i* measurements with rotation periods from K2, we constrain the line-of-sight inclinations of ROXs 12 A and 2MASS J16262774–2527247 and find that they are misaligned by 60^(+7)_(-11)°. In addition, the orbital axis of ROXs 12 B is likely misaligned from the spin axis of its host star, ROXs 12 A, suggesting that ROXs 12 B formed akin to fragmenting binary stars or in an equatorial disk that was torqued by the wide stellar tertiary.
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the young substellar companion roxs 12 b near infrared Spectrum system architecture and spin orbit misalignment
arXiv: Earth and Planetary Astrophysics, 2017Co-Authors: Brendan P Bowler, Gregory N Mace, Adam L Kraus, Marta L Bryan, Heather A Knutson, Matteo Brogi, Aaron C Rizzuto, Andrew Vanderburg, Michael C Liu, Lynne A HillenbrandAbstract:ROXs 12 (2MASS J16262803-2526477) is a young star hosting a directly imaged companion near the deuterium-burning limit. We present a suite of spectroscopic, imaging, and time-series observations to characterize the physical and environmental properties of this system. Moderate-resolution Near-Infrared spectroscopy of ROXs 12 B from Gemini-North/NIFS and Keck/OSIRIS reveals signatures of low surface gravity including weak alkali absorption lines and a triangular $H$-band pseudo-continuum shape. No signs of Pa$\beta$ emission are evident. As a population, however, we find that about half (46 $\pm$ 14\%) of young ($\lesssim$15 Myr) companions with masses $\lesssim$20 $M_\mathrm{Jup}$ possess actively accreting subdisks detected via Pa$\beta$ line emission, which represents a lower limit on the prevalence of circumplanetary disks in general as some are expected to be in a quiescent phase of accretion. The bolometric luminosity of the companion and age of the host star (6$^{+4}_{-2}$ Myr) imply a mass of 17.5 $\pm$ 1.5 $M_\mathrm{Jup}$ for ROXs 12 B based on hot-start evolutionary models. We identify a wide (5100 AU) tertiary companion to this system, 2MASS J16262774-2527247, which is heavily accreting and exhibits stochastic variability in its $K2$ light curve. By combining $v$sin$i_*$ measurements with rotation periods from $K2$, we constrain the line-of-sight inclinations of ROXs 12 A and 2MASS J16262774-2527247 and find that they are misaligned by 60$^{+7}_{-11}$$^{\circ}$. In addition, the orbital axis of ROXs 12 B is likely misaligned from the spin axis of its host star ROXs 12 A, suggesting that ROXs 12 B formed akin to fragmenting binary stars or in an equatorial disk that was torqued by the wide stellar tertiary.
Christopher M. Dodson - One of the best experts on this subject based on the ideXlab platform.
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Magnetic dipole and electric quadrupole transitions in the trivalent lanthanide series: Calculated emission rates and oscillator strengths
Physical Review B, 2012Co-Authors: Christopher M. Dodson, Rashid ZiaAbstract:Given growing interest in optical-frequency magnetic dipole transitions, we use intermediate coupling calculations to identify strong magnetic dipole emission lines that are well suited for experimental study. The energy levels for all trivalent lanthanide ions in the $4{f}^{\text{n}}$ configuration are calculated using a detailed free ion Hamiltonian, including electrostatic and spin-orbit terms as well as two-body, three-body, spin-spin, spin-other-orbit, and electrostatically correlated spin-orbit interactions. These free ion energy levels and eigenstates are then used to calculate the oscillator strengths for all ground-state magnetic dipole absorption lines and the spontaneous emission rates for all magnetic dipole emission lines including transitions between excited states. A large number of strong magnetic dipole transitions are predicted throughout the visible and Near-Infrared Spectrum, including many at longer wavelengths that would be ideal for experimental investigation of magnetic light-matter interactions with optical metamaterials and plasmonic antennas.
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magnetic dipole and electric quadrupole transitions in the trivalent lanthanide series calculated emission rates and oscillator strengths
Physical Review B, 2012Co-Authors: Christopher M. DodsonAbstract:Given growing interest in optical-frequency magnetic dipole transitions, we use intermediate coupling calculations to identify strong magnetic dipole emission lines that are well suited for experimental study. The energy levels for all trivalent lanthanide ions in the 4f n configuration are calculated using a detailed free ion Hamiltonian, including electrostatic and spin-orbit terms as well as two-body, three-body, spin-spin, spin-other-orbit, and electrostatically correlated spin-orbit interactions. These free ion energy levels and eigenstates are then used to calculate the oscillator strengths for all ground-state magnetic dipole absorption lines and the spontaneous emission rates for all magnetic dipole emission lines including transitions between excited states. A large number of strong magnetic dipole transitions are predicted throughout the visible and Near-Infrared Spectrum, including many at longer wavelengths that would be ideal for experimental investigation of magnetic light-matter interactions with optical metamaterials and plasmonic antennas.
