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Kengo Tomida - One of the best experts on this subject based on the ideXlab platform.
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revealing a detailed mass distribution of a high Density Core mc27 l1521f in taurus with alma
The Astrophysical Journal, 2016Co-Authors: Kazuki Tokuda, Toshikazu Onishi, Tomoaki Matsumoto, Kazuya Saigo, Akiko Kawamura, Y Fukui, Shuichiro Inutsuka, Masahiro N Machida, Kengo Tomida, Kengo TachiharaAbstract:We present the results of ALMA observations of dust continuum emission and molecular rotational lines toward a dense Core MC27 (aka L1521F) in Taurus, which is considered to be at a very early stage of star formation. The detailed column Density distributions on size scales from a few tens to ~10,000 AU are revealed by combining the ALMA (12 m array + 7 m array) data with the published/unpublished single-dish data. The high angular resolution observations at 0.87 mm with a synthesized beam size of ~074 × 032 reveal that a protostellar source, MMS-1, is not spatially resolved and lacks associated gas emission, while a starless high-Density Core, MMS-2, has substructures in both dust and molecular emission. The averaged radial column Density distribution of the inner part of MC27/L1521F (r 3000 AU) is ~ , clearly flatter than that of the outer part, ~. The complex velocity/spatial structure obtained with previous ALMA observations is located inside the inner flatter region, which may reflect the dynamical status of the dense Core.
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revealing a detailed mass distribution of a high Density Core mc27 l1521f in taurus with alma
arXiv: Astrophysics of Galaxies, 2016Co-Authors: Kazuki Tokuda, Toshikazu Onishi, Tomoaki Matsumoto, Kazuya Saigo, Akiko Kawamura, Y Fukui, Shuichiro Inutsuka, Masahiro N Machida, Kengo Tomida, Kengo TachiharaAbstract:We present the results of ALMA observations of dust continuum emission and molecular rotational lines toward a dense Core MC27 (aka L1521F) in Taurus, which is considered to be at a very early stage of star formation. The detailed column Density distribution on size scales from a few tens AU to ~10,000 AU scale are revealed by combining the ALMA (12 m array + 7 m array) data with the published/unpublished single-dish data. The high angular resolution observations at 0.87 mm with a synthesized beam size of ~0."74 x 0."32 reveal that a protostellar source, MMS-1, is not spatially resolved and lacks associated gas emission, while a starless high-Density Core, MMS-2, has substructures both in dust and molecular emission. The averaged radial column Density distribution of the inner part of MC27/L1521F (r $\lesssim$ 3000 AU) is N(H2) ~r$^{-0.4}$, clearly flatter than that of the outer part, ~r$^{-1.0}$. The complex velocity/spatial structure obtained with previous ALMA observations is located inside the inner flatter region, which may reflect the dynamical status of the dense Core.
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alma observations of a high Density Core in taurus dynamical gas interaction at the possible site of a multiple star formation
From Interstellar Clouds to Star-Forming Galaxies: Universal Processes?, 2015Co-Authors: Kazuki Tokuda, Toshikazu Onishi, Tomoaki Matsumoto, Kazuya Saigo, Akiko Kawamura, Y Fukui, Shuichiro Inutsuka, Masahiro N Machida, Kengo TomidaAbstract:Starless dense Cores eventually collapse dynamically, which forms protostars inside them, and the physical properties of the Cores determine the nature of the forming protostars. We report ALMA observations of dust continuum emission and molecular rotational lines toward MC27 or L1521F, which is considered to be very close to the first protostellar Core phase. We found a few starless high-Density Cores, one of which has a very high Density of∼10cm, within a region of several hundred AU around a very low-luminosity protostar detected by Spitzer. A very compact bipolar outflow with a dynamical timescale of a few hundred years was found toward the protostar. The molecular line observation shows several Cores with an arc-like structure, possibly due to the dynamical gas interaction. These complex structures revealed in the present observations suggest that the initial condition of star formation is highly dynamical in nature, which is considered to be a key factor in understanding fundamental issues of star formation such as the formation of multiple stars and the origin of the initial mass function of stars. Subject headings: ISM: clouds — ISM: kinematics and dynamics — ISM: molecules — stars: formation
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alma observations of a high Density Core in taurus dynamical gas interaction at the possible site of a multiple star formation
The Astrophysical Journal, 2014Co-Authors: Kazuki Tokuda, Toshikazu Onishi, Tomoaki Matsumoto, Kazuya Saigo, Akiko Kawamura, Y Fukui, Shuichiro Inutsuka, Masahiro N Machida, Kengo TomidaAbstract:Starless dense Cores eventually collapse dynamically, forming protostars inside them, and the physical properties of the Cores determine the nature of the forming protostars. We report ALMA observations of dust continuum emission and molecular rotational lines toward MC27 or L1521F, which is considered to be very close to the first protostellar Core phase. We found a few starless high-Density Cores, one of which has a very high Density of ∼10{sup 7} cm{sup –3}, within a region of several hundred AU around a very low-luminosity protostar detected by Spitzer. A very compact bipolar outflow with a dynamical timescale of a few hundred years was found toward the protostar. The molecular line observation shows several Cores with an arc-like structure, possibly due to the dynamical gas interaction. These complex structures revealed in the present observations suggest that the initial condition of star formation is highly dynamical in nature, which is considered to be a key factor in understanding fundamental issues of star formation such as the formation of multiple stars and the origin of the initial mass function of stars.
W J G De Blok - One of the best experts on this subject based on the ideXlab platform.
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high resolution dark matter Density profiles of things dwarf galaxies correcting for noncircular motions
The Astronomical Journal, 2008Co-Authors: Seheon Oh, Fabian Walter, W J G De Blok, Elias Brinks, Robert C KennicuttAbstract:We present a new method to remove the impact of random and small-scale noncircular motions from H I velocity fields in (dwarf) galaxies in order to better constrain the dark matter properties for these objects. This method extracts the circularly rotating velocity components from the H I data cube and condenses them into a so-called bulk velocity field. We derive high-resolution (~0.2 kpc) rotation curves of IC 2574 and NGC 2366 based on bulk velocity fields derived from The H I Nearby Galaxy Survey obtained at the Very Large Array. We compare the bulk velocity field rotation curves with those derived from the traditional intensity-weighted mean velocity fields and find significant differences. The bulk velocity field rotation curves are significantly less affected by noncircular motions and constrain the dark matter distribution in our galaxies, allowing us to address the discrepancy between the inferred and predicted dark matter distribution in galaxies (the "cusp/Core" problem). Spitzer Infrared Nearby Galaxies Survey 3.6 μm data, which are largely unaffected by dust in these systems, as well as ancillary optical information, are used to separate the contribution of the baryons from the total matter content. Using stellar population synthesis models, assuming various sets of metallicity and star-formation histories, we compute stellar mass-to-light ratios for the 3.6 μm and 4.5 μm bands. Using our predicted value for the 3.6 μm stellar mass-to-light ratio, we find that the observed dark matter distributions of IC 2574 and NGC 2366 are inconsistent with the cusp-like dark matter halo predicted by Λ Cold Dark Matter models, even after corrections for noncircular motions. This result also holds for other assumptions about the stellar mass-to-light ratio. The distribution of dark matter within our sample galaxies is best described by models with a kpc-sized constant-Density Core.
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high resolution rotation curves and galaxy mass models from things
The Astronomical Journal, 2008Co-Authors: W J G De Blok, Fabian Walter, Elias Brinks, C Trachternach, Robert C KennicuttAbstract:We present rotation curves of 19 galaxies from The H I Nearby Galaxy Survey (THINGS). The high spatial and velocity resolution of THINGS make these the highest quality H I rotation curves available to date for a large sample of nearby galaxies, spanning a wide range of H I masses and luminosities. The high quality of the data allows us to derive the geometric and dynamical parameters using H I data alone. We do not find any declining rotation curves unambiguously associated with a cut-off in the mass distribution out to the last measured point. The rotation curves are combined with 3.6 μm data from the Spitzer Infrared Nearby Galaxies Survey to construct mass models. Our best-fit dynamical disk masses, derived from the rotation curves, are in good agreement with photometric disk masses derived from the 3.6 μm images in combination with stellar population synthesis arguments and two different assumptions for the stellar initial mass function (IMF). We test the cold dark matter (CDM) motivated cusp model, and the observationally motivated central Density Core model and find that (independent of IMF) for massive, disk-dominated galaxies, all halo models fit apparently equally well; for low-mass galaxies, however, a Core-dominated halo is clearly preferred over a cusp-like halo. The empirically derived densities of the dark matter halos of the late-type galaxies in our sample are half of what is predicted by CDM simulations, again independent of the assumed IMF.
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high resolution rotation curves and galaxy mass models from things
arXiv: Astrophysics, 2008Co-Authors: W J G De Blok, Fabian Walter, Elias Brinks, C Trachternach, Robert C KennicuttAbstract:We present rotation curves of 19 galaxies from THINGS, The HI Nearby Galaxy Survey. The high spatial and velocity resolution of THINGS make these the highest quality HI rotation curves available to date for a large sample of nearby galaxies, spanning a wide range of HI masses and luminosities. The high quality of the data allows us to derive the geometrical and dynamical parameters using HI data alone. We do not find any declining rotation curves unambiguously associated with a cut-off in the mass distribution out to the last measured point. The rotation curves are combined with 3.6 um data from SINGS (Spitzer Infrared Nearby Galaxies Survey) to construct mass models. Our best-fit, dynamical disk masses, derived from the rotation curves, are in good agreement with photometric disk masses derived from the 3.6 um images in combination with stellar population synthesis arguments and two different assumptions for the stellar Initial Mass Function (IMF). We test the Cold Dark Matter-motivated cusp model, and the observationally motivated central Density Core model and find that (independent of IMF) for massive, disk-dominated galaxies, all halo models fit apparently equally well; for low-mass galaxies, however, a Core-dominated halo is clearly preferred over a cuspy halo. The empirically derived densities of the dark matter halos of the late-type galaxies in our sample are half of what is predicted by CDM simulations, again independent of the assumed IMF.
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mass Density profiles of low surface brightness galaxies
The Astrophysical Journal, 2001Co-Authors: W J G De Blok, Stacy S Mcgaugh, A Bosma, Vera C RubinAbstract:We derive the mass Density profiles of dark matter halos that are implied by high spatial resolution rotation curves of low surface brightness galaxies. We find that, at small radii, the mass Density distribution is dominated by a nearly constant Density Core with a Core radius of a few kiloparsecs. For ρ(r) ~ rα, the distribution of inner slopes α is strongly peaked around α = -0.2. This is significantly shallower than the cuspy α ≤ -1 halos found in cold dark matter simulations. While the observed distribution of α does have a tail toward such extreme values, the derived value of α is found to depend on the spatial resolution of the rotation curves: α ≈ -1 is found only for the least well resolved galaxies. Even for these galaxies, our data are also consistent with constant-Density Cores (α = 0) of modest (~1 kpc) Core radius, which can give the illusion of steep cusps when insufficiently resolved. Consequently, there is no clear evidence for a cuspy halo in any of the low surface brightness galaxies observed.
Takashi Sasaki - One of the best experts on this subject based on the ideXlab platform.
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125 μm cladding eight Core multi Core fiber realizing ultra high Density cable suitable for o band short reach optical interconnects
Journal of Lightwave Technology, 2016Co-Authors: Tetsuya Hayashi, Tetsuya Nakanishi, Kaoru Hirashima, Osamu Shimakawa, Fumiaki Sato, Koichi Koyama, Akira Furuya, Yasunori Murakami, Takashi SasakiAbstract:A novel multi-Core fiber (MCF), having eight Cores within a 125-μm-diameter cladding and suitable for short-reach transmissions, is proposed. By optimizing O-band transmission, the proposed MCF realized the high-Density Core packing simultaneously achieving the optical characteristics comparable to those of the standard single-mode fiber in O-band, where low material dispersion can be leveraged. The standard 125-μm-diameter cladding is compatible with conventional cabling/connecting technologies and has the tightly bendable mechanical reliability proven by the widely installed standard optical fibers. An ultra-high-Density 12-MCF cable was fabricated with the proposed MCF, and achieved 13.6 Cores/mm 2 (96 Cores in the 3-mm-diameter cable). The transmission characteristics of the cabled MCF were evaluated using a 100GBASE-LR4 transceiver, and error-free 8-SDM × 4-WDM × 25-Gb/s (800-Gb/s/fiber) signals in O-band were successfully transmitted over the 1.11-km-long cabled MCF.
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125 μm cladding eight Core multi Core fiber realizing ultra high Density cable suitable for o band short reach optical interconnects
Journal of Lightwave Technology, 2016Co-Authors: Tetsuya Hayashi, Tetsuya Nakanishi, Kaoru Hirashima, Osamu Shimakawa, Fumiaki Sato, Koichi Koyama, Akira Furuya, Yasunori Murakami, Takashi SasakiAbstract:A novel multi-Core fiber (MCF), having eight Cores within a 125-μm-diameter cladding and suitable for short-reach transmissions, is proposed. By optimizing O-band transmission, the proposed MCF realized the high-Density Core packing simultaneously achieving the optical characteristics comparable to those of the standard single-mode fiber in O-band, where low material dispersion can be leveraged. The standard 125-μm-diameter cladding is compatible with conventional cabling/connecting technologies and has the tightly bendable mechanical reliability proven by the widely installed standard optical fibers. An ultra-high-Density 12-MCF cable was fabricated with the proposed MCF, and achieved 13.6 Cores/mm2 (96 Cores in the 3-mm-diameter cable). The transmission characteristics of the cabled MCF were evaluated using a 100GBASE-LR4 transceiver, and error-free 8-SDM × 4-WDM × 25-Gb/s (800-Gb/s/fiber) signals in O-band were successfully transmitted over the 1.11-km-long cabled MCF.
Edouard Tollet - One of the best experts on this subject based on the ideXlab platform.
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nihao iv Core creation and destruction in dark matter Density profiles across cosmic time
Monthly Notices of the Royal Astronomical Society, 2016Co-Authors: Edouard Tollet, Andrea V Maccio, Aaron A Dutton, G Stinson, Liang Wang, Camilla PenzoAbstract:We use the NIHAO simulations to investigate the effects of baryonic physics on the time evolution of Dark Matter central Density profiles. The sample is made of $\approx 70$ independent high resolution hydrodynamical simulations of galaxy formation and covers a wide mass range: 1e10< Mhalo <1e12, i.e., from dwarfs to L* . We confirm previous results on the dependence of the inner dark matter Density slope, $\alpha$, on the ratio between stellar-to-halo mass. We show that this relation holds approximately at all redshifts (with an intrinsic scatter of ~0.18 in $\alpha$). This implies that in practically all haloes the shape of their inner Density profile changes quite substantially over cosmic time, as they grow in stellar and total mass. Thus, depending on their final stellar-to-halo mass ratio, haloes can either form and keep a substantial Density Core (size~1 kpc), or form and then destroy the Core and re-contract the halo, going back to a cuspy profile, which is even steeper than CDM predictions for massive galaxies (~1e12 Msun). We show that results from the NIHAO suite are in good agreement with recent observational measurements of $\alpha$ in dwarf galaxies. Overall our results suggest that the notion of a universal Density profile for dark matter haloes is no longer valid in the presence of galaxy formation.
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nihao iv Core creation and destruction in dark matter Density profiles across cosmic time
Monthly Notices of the Royal Astronomical Society, 2016Co-Authors: Edouard Tollet, Andrea V Maccio, Aaron A Dutton, Liang Wang, Greg S Stinson, Camilla PenzoAbstract:We use the NIHAO (Numerical Investigation of Hundred Astrophysical Objects) cosmological simulations to investigate the effects of baryonic physics on the time evolution of dark matter central Density profiles. The sample is made of ≈70 independent high-resolution hydrodynamical simulations of galaxy formation and covers a wide mass range: 1010 ≲ Mhalo/M⊙ ≲ 1012, i.e. from dwarfs to L*. We confirm previous results on the dependence of the inner dark matter Density slope, α, on the ratio between stellar-to-halo mass, Mstar/Mhalo. We show that this relation holds approximately at all redshifts (with an intrinsic scatter of ~0.18 in α measured between 1 and 2 per cent of the virial radius). This implies that in practically all haloes the shape of their inner Density profile changes quite substantially over cosmic time, as they grow in stellar and total mass. Thus, depending on their final Mstar/Mhalo ratio, haloes can either form and keep a substantial Density Core (RCore ~ 1 kpc), or form and then destroy the Core and recontract the halo, going back to a cuspy profile, which is even steeper than cold-dark-matter predictions for massive galaxies (1012 M⊙). We show that results from the NIHAO suite are in good agreement with recent observational measurements of α in dwarf galaxies. Overall our results suggest that the notion of a universal Density profile for dark matter haloes is no longer valid in the presence of galaxy formation.
Kazuki Tokuda - One of the best experts on this subject based on the ideXlab platform.
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revealing a detailed mass distribution of a high Density Core mc27 l1521f in taurus with alma
The Astrophysical Journal, 2016Co-Authors: Kazuki Tokuda, Toshikazu Onishi, Tomoaki Matsumoto, Kazuya Saigo, Akiko Kawamura, Y Fukui, Shuichiro Inutsuka, Masahiro N Machida, Kengo Tomida, Kengo TachiharaAbstract:We present the results of ALMA observations of dust continuum emission and molecular rotational lines toward a dense Core MC27 (aka L1521F) in Taurus, which is considered to be at a very early stage of star formation. The detailed column Density distributions on size scales from a few tens to ~10,000 AU are revealed by combining the ALMA (12 m array + 7 m array) data with the published/unpublished single-dish data. The high angular resolution observations at 0.87 mm with a synthesized beam size of ~074 × 032 reveal that a protostellar source, MMS-1, is not spatially resolved and lacks associated gas emission, while a starless high-Density Core, MMS-2, has substructures in both dust and molecular emission. The averaged radial column Density distribution of the inner part of MC27/L1521F (r 3000 AU) is ~ , clearly flatter than that of the outer part, ~. The complex velocity/spatial structure obtained with previous ALMA observations is located inside the inner flatter region, which may reflect the dynamical status of the dense Core.
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revealing a detailed mass distribution of a high Density Core mc27 l1521f in taurus with alma
arXiv: Astrophysics of Galaxies, 2016Co-Authors: Kazuki Tokuda, Toshikazu Onishi, Tomoaki Matsumoto, Kazuya Saigo, Akiko Kawamura, Y Fukui, Shuichiro Inutsuka, Masahiro N Machida, Kengo Tomida, Kengo TachiharaAbstract:We present the results of ALMA observations of dust continuum emission and molecular rotational lines toward a dense Core MC27 (aka L1521F) in Taurus, which is considered to be at a very early stage of star formation. The detailed column Density distribution on size scales from a few tens AU to ~10,000 AU scale are revealed by combining the ALMA (12 m array + 7 m array) data with the published/unpublished single-dish data. The high angular resolution observations at 0.87 mm with a synthesized beam size of ~0."74 x 0."32 reveal that a protostellar source, MMS-1, is not spatially resolved and lacks associated gas emission, while a starless high-Density Core, MMS-2, has substructures both in dust and molecular emission. The averaged radial column Density distribution of the inner part of MC27/L1521F (r $\lesssim$ 3000 AU) is N(H2) ~r$^{-0.4}$, clearly flatter than that of the outer part, ~r$^{-1.0}$. The complex velocity/spatial structure obtained with previous ALMA observations is located inside the inner flatter region, which may reflect the dynamical status of the dense Core.
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alma observations of a high Density Core in taurus dynamical gas interaction at the possible site of a multiple star formation
From Interstellar Clouds to Star-Forming Galaxies: Universal Processes?, 2015Co-Authors: Kazuki Tokuda, Toshikazu Onishi, Tomoaki Matsumoto, Kazuya Saigo, Akiko Kawamura, Y Fukui, Shuichiro Inutsuka, Masahiro N Machida, Kengo TomidaAbstract:Starless dense Cores eventually collapse dynamically, which forms protostars inside them, and the physical properties of the Cores determine the nature of the forming protostars. We report ALMA observations of dust continuum emission and molecular rotational lines toward MC27 or L1521F, which is considered to be very close to the first protostellar Core phase. We found a few starless high-Density Cores, one of which has a very high Density of∼10cm, within a region of several hundred AU around a very low-luminosity protostar detected by Spitzer. A very compact bipolar outflow with a dynamical timescale of a few hundred years was found toward the protostar. The molecular line observation shows several Cores with an arc-like structure, possibly due to the dynamical gas interaction. These complex structures revealed in the present observations suggest that the initial condition of star formation is highly dynamical in nature, which is considered to be a key factor in understanding fundamental issues of star formation such as the formation of multiple stars and the origin of the initial mass function of stars. Subject headings: ISM: clouds — ISM: kinematics and dynamics — ISM: molecules — stars: formation
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alma observations of a high Density Core in taurus dynamical gas interaction at the possible site of a multiple star formation
The Astrophysical Journal, 2014Co-Authors: Kazuki Tokuda, Toshikazu Onishi, Tomoaki Matsumoto, Kazuya Saigo, Akiko Kawamura, Y Fukui, Shuichiro Inutsuka, Masahiro N Machida, Kengo TomidaAbstract:Starless dense Cores eventually collapse dynamically, forming protostars inside them, and the physical properties of the Cores determine the nature of the forming protostars. We report ALMA observations of dust continuum emission and molecular rotational lines toward MC27 or L1521F, which is considered to be very close to the first protostellar Core phase. We found a few starless high-Density Cores, one of which has a very high Density of ∼10{sup 7} cm{sup –3}, within a region of several hundred AU around a very low-luminosity protostar detected by Spitzer. A very compact bipolar outflow with a dynamical timescale of a few hundred years was found toward the protostar. The molecular line observation shows several Cores with an arc-like structure, possibly due to the dynamical gas interaction. These complex structures revealed in the present observations suggest that the initial condition of star formation is highly dynamical in nature, which is considered to be a key factor in understanding fundamental issues of star formation such as the formation of multiple stars and the origin of the initial mass function of stars.