We calculate optical properties from several aerosol models using same assumptions. We test choic... more We calculate optical properties from several aerosol models using same assumptions. We test choices on mixing state, refractive index, density and hygroscopicity. The most sensitive parameter is the aerosol mixing state. The related uncertainty on calculated AOD and SSA is 30e35%.
Proceedings of the International Astronomical Union, 2005
Chandra images of the elliptical galaxy NGC 4261 have revealed an anisotropy in the spatial distr... more Chandra images of the elliptical galaxy NGC 4261 have revealed an anisotropy in the spatial distribution of the off-nuclear X-ray sources, interpreted by Zezas et al. as evidence of an association with a young stellar population. Our independent analysis of archive X-ray (Chandra) and optical (INT and HST) observations confirms the anisotropy of the X-ray sources but conducts to a different interpretation for their origin. We find that nearly half of the X-ray sources are associated to a globular cluster (optical counterpart) suggesting that they are accreting low-mass X-ray binaries. Where color index information is available, the X-ray sources are found to reside in red (metal-rich) systems. The luminosity function of the X-ray sources is also consistent with the one drawn from a population of Low Mass X-ray Binaries. We further investigate the properties of the sample of point-like sources obtained from archival optical images that we suggest are good globular cluster candidates and for which we find that the projected spatial distribution is non-homogeneous. In addition, we show that the distributions of the optical and X-ray populations are very similar, which leads us to conclude that the spatial anisotropy of the X-ray sources in NGC 4261 is mostly a reflection of the anisotropy of the globular cluster population.
Chandra images of the elliptical galaxy NGC 4261 have revealed an anisotropy in the spatial distr... more Chandra images of the elliptical galaxy NGC 4261 have revealed an anisotropy in the spatial distribution of the off-nuclear X-ray sources, interpreted by Zezas et al. as evidence of an association with a young stellar population. Our independent analysis of archive X-ray (Chandra) and optical (INT and HST) observations confirms the anisotropy of the X-ray sources but conducts to a different interpretation for their origin. We find that nearly half of the X-ray sources are associated to a globular cluster (optical counterpart) suggesting that they are accreting low-mass X-ray binaries. Where color index information is available, the X-ray sources are found to reside in red (metal-rich) systems. The luminosity function of the X-ray sources is also consistent with the one drawn from a population of Low Mass X-ray Binaries. We further investigate the properties of the sample of point-like sources obtained from archival optical images that we suggest are good globular cluster candidates and for which we find that the projected spatial distribution is non-homogeneous. In addition, we show that the distributions of the optical and X-ray populations are very similar, which leads us to conclude that the spatial anisotropy of the X-ray sources in NGC 4261 is mostly a reflection of the anisotropy of the globular cluster population.
By ab initio calculations, we show that when two H vacancies occupy neighboring fcc sites on a hy... more By ab initio calculations, we show that when two H vacancies occupy neighboring fcc sites on a hydrogen-covered Pd(1 1 1) surface, a very low-barrier process exists, leading to a fast effective rotation of the divacancy. As a consequence, divacancies are likely to display a three lobed shape in typical STM images, as reported in a recent experimental work [T. Mitsui, M.K. Rose, E. Fomin, D.F. Ogletree, M. Salmeron, Nature 422 ]. Our results allow for a better understanding of the experimental data, in showing the atomic-scale path responsible for the rotation and in providing a theoretical estimate of the activation energy of the process.
We calculate optical properties from several aerosol models using same assumptions. We test choic... more We calculate optical properties from several aerosol models using same assumptions. We test choices on mixing state, refractive index, density and hygroscopicity. The most sensitive parameter is the aerosol mixing state. The related uncertainty on calculated AOD and SSA is 30e35%.
The Air Quality Model Evaluation International Initiative (AQMEII) has now reached its second pha... more The Air Quality Model Evaluation International Initiative (AQMEII) has now reached its second phase which is dedicated to the evaluation of online coupled chemistry-meteorology models. Sixteen modelling groups from Europe and five from North America have run regional air quality models to simulate the year 2010 over one European and one North American domain. The MACC re-analysis has been used as chemical initial (IC) and boundary conditions (BC) by all participating regional models in AQMEII-2. The aim of the present work is to evaluate the MACC re-analysis along with the participating regional models against a set of ground-based measurements (O 3 , CO, NO, NO 2 , SO 2 , SO 4 2-) and vertical profiles (O 3 and CO). Results indicate different degrees of agreement between the measurements and the MACC re-analysis, with an overall better performance over the North American domain. The influence of BC on regional air quality simulations is analyzed in a qualitative way by contrasting model performance for the MACC re-analysis with that for the regional models. This approach complements more quantitative approaches documented in the literature that often have involved sensitivity simulations but typically were limited to only one or only a few regional scale models. Results suggest an important influence of the BC on ozone for which the underestimation in winter in the MACC re-analysis is mimicked by the regional models. For CO, it is found that background concentrations near the domain boundaries are rather close to observations while those over the interior of the two continents are underpredicted by both MACC and the regional models over Europe but only by MACC over North America. This indicates that emission differences between the MACC re-analysis and the regional models can have a profound impact on model performance and points to the need for harmonization of inputs in future linked global/regional modeling studies.
Comparative analysis of meteorological performance of coupled chemistry-meteorology models in the... more Comparative analysis of meteorological performance of coupled chemistry-meteorology models in the context of AQMEII phase 2, Atmospheric Environment (2015), Abstract 53 Air pollution simulations critically depend on the quality of the underlying meteorology. In 54 phase 2 of the Air Quality Model Evaluation International Initiative (AQMEII-2), thirteen 55 modeling groups from Europe and four groups from North America operating eight 56 different regional coupled chemistry and meteorology models participated in a coordinated 57 model evaluation exercise. Each group simulated the year 2010 for a domain covering 58 either Europe or North America or both. Here were present an operational analysis of 59 model performance with respect to key meteorological variables relevant for atmospheric 60 chemistry processes and air quality. These parameters include temperature and wind speed 61 at the surface and in the vertical profile, incoming solar radiation at the ground, 62 precipitation, and planetary boundary layer heights. A similar analysis was performed 63 during AQMEII phase 1 (Vautard et al., 2012) for offline air quality models not directly 64 coupled to the meteorological model core as the model systems investigated here. Similar 65 to phase 1, we found significant overpredictions of 10-m wind speeds by most models, 66 more pronounced during night than during daytime. The seasonal evolution of temperature 67 was well captured with monthly mean biases below 2 K over all domains. Solar incoming 68 radiation, precipitation and PBL heights, on the other hand, showed significant spread 69 between models and observations suggesting that major challenges still remain in the 70 simulation of meteorological parameters relevant for air quality and for chemistry -71 climate interactions at the regional scale.
The formulations of tropospheric gas-phase chemistry ("mechanisms") anuscript lick here to downlo... more The formulations of tropospheric gas-phase chemistry ("mechanisms") anuscript lick here to download Manuscript: knote_et_al_manuscript_20141127.tex Click here to view linked References 157 2.5. Emissions 158 We test the mechanisms under a realistic range of emission conditions. 159 Therefore, we employ the exact emission input (2-D time-varying fields of 160 12
The simultaneous, diffusion-controlled growth of GdFeO3 (perovskite) and Gd3Fe5O12 (garnet) was s... more The simultaneous, diffusion-controlled growth of GdFeO3 (perovskite) and Gd3Fe5O12 (garnet) was studied at 1200–1400 °C in Gd2O3–Fe2O3 diffusion couples. Both compounds were found to grow as parallel layers according to the parabolic rate law. The parabolic rate constants of the second kind for the exclusive growth of each compound (k1II for GdFeO3, k2II for Gd3Fe5O12) were calculated from the experimentally
Monthly Notices of the Royal Astronomical Society, 2007
Chandra and XM M −N ewton observations of the Cartwheel galaxy show ∼ 17 bright X-ray sources ( >... more Chandra and XM M −N ewton observations of the Cartwheel galaxy show ∼ 17 bright X-ray sources ( > ∼ 5 × 10 38 erg s −1 ), all within the gas-rich outer ring. We explore the hypothesis that these X-ray sources are powered by intermediate-mass black holes (IMBHs) accreting gas or undergoing mass transfer from a stellar companion. To this purpose, we run N -body/SPH simulations of the galaxy interaction which might have led to the formation of Cartwheel, tracking the dynamical evolution of two different IMBH populations: halo and disc IMBHs. Halo IMBHs cannot account for the observed X-ray sources, as only a few of them cross the outer ring. Instead, more than half of the disc IMBHs are pulled in the outer ring as a consequence of the galaxy collision. However, also in the case of disc IMBHs, accretion from surrounding gas clouds cannot account for the high luminosities of the observed sources. Finally, more than 500 disc IMBHs are required to produce < ∼ 15 X-ray sources via mass transfer from very young stellar companions. Such number of IMBHs is very large and implies extreme assumptions. Thus, the hypothesis that all the observed X-ray sources in Cartwheel are associated with IMBHs is hardly consistent with our simulations, even if it is still possible that IMBHs account for the few ( < ∼ 1 − 5) brightest ultraluminous X-ray sources (ULXs).
We detect ionized gas characteristics indicative of winds in three disk-dominated galaxies that a... more We detect ionized gas characteristics indicative of winds in three disk-dominated galaxies that are members of a super-group at z = 0.37 that will merge to form a Coma-mass cluster. All three galaxies are IR-luminous (L IR > 4 × 10 10 L ⊙ , SFR > 8 M ⊙ yr −1 ) and lie outside the X-ray cores of the galaxy groups. We find that the most IR-luminous galaxy has strong blue and redshifted emission lines with velocities of ∼ ±200 km s −1 and a third, blueshifted (∼ 900 km s −1 ) component. This galaxy's line-widths (Hβ, [OIII]λ5007, [NII], Hα) correspond to velocities of 100 − 1000 km s −1 . We detect extraplanar gas in two of three galaxies with SFR > 8 M ⊙ yr −1 whose orientations are approximately edge-on and which have IFU spaxels off the stellar disk. IFU maps reveal that the extraplanar gas extends to r h ∼ 10 kpc; [NII] and Hα line-widths correspond to velocities of ∼ 200 − 400 km s −1 in the disk and decrease to ∼ 50 − 150 km s −1 above the disk. Multi-wavelength observations indicate that the emission is dominated by star formation. Including the most IR-luminous galaxy we find that 18% of supergroup members with SFR > 8 M ⊙ yr −1 show ionized gas characteristics indicative of outflows. This is a lower limit as showing that gas is outflowing in the remaining, moderately inclined, galaxies requires a non-trivial decoupling of contributions to the emission lines from rotational and turbulent motion. Ionized gas mass loss in these winds is ∼ 0.1 M ⊙ yr −1 for each galaxy, although the winds are likely to entrain significantly larger amounts of mass in neutral and molecular gas.
We investigate possible environmental and morphological trends in the z ∼ 0 bar fraction using tw... more We investigate possible environmental and morphological trends in the z ∼ 0 bar fraction using two carefully selected samples representative of a low-density environment (the isolated galaxies from the AMIGA sample) and of a dense environment (galaxies in the Virgo cluster). Galaxies span a stellar mass range from 10 8 to 10 12 M and are visually classified using both high-resolution NIR (H-band) imaging and optical rgb images. We find that the bar fraction in disk galaxies is independent of environment suggesting that bar formation may occur prior to the formation of galaxy clusters. The bar fraction in early type spirals (Sa − Sb) is ∼50%, which is twice as high as the late type spirals (Sbc − Sm). The higher bar fraction in early type spirals may be due to the fact that a significant fraction of their bulges are pseudo-bulges which form via the buckling instability of a bar. i.e. a large part of the Hubble sequence is due to secular processes which move disc galaxies from late to early types. There is a hint of a higher bar fraction with higher stellar masses which may be due to the susceptibility to bar instabilities as the baryon fractions increase in halos of larger masses. Overall, the S0 population has a lower bar fraction than the Sa − Sb galaxies and their barred fraction drops significantly with decreasing stellar mass. This supports the notion that S0s form via the transformation of disk galaxies that enter the cluster environment. The gravitational harassment thickens the stellar disks, wiping out spiral patterns and eventually erasing the bar -a process that is more effective at lower galaxy masses.
Giant low surface brightness galaxies (GLSBs) have flat discs extending up to ∼ 100 kpc. Their fo... more Giant low surface brightness galaxies (GLSBs) have flat discs extending up to ∼ 100 kpc. Their formation is a puzzle for cosmological simulations in the cold dark matter scenario. We suggest that GLSBs might be the final product of the evolution of collisional ring galaxies. In fact, our simulations show that, approximately 0.5 − 1.5 Gyr after the collision which led to the formation of the ring galaxy, the ring keeps expanding and fades, while the disc becomes very large (∼ 100 kpc) and flat. At this stage, our simulated galaxies match many properties of GLSBs (surface brightness profile, morphology, HI spectrum and rotation curve).
We calculate optical properties from several aerosol models using same assumptions. We test choic... more We calculate optical properties from several aerosol models using same assumptions. We test choices on mixing state, refractive index, density and hygroscopicity. The most sensitive parameter is the aerosol mixing state. The related uncertainty on calculated AOD and SSA is 30e35%.
Proceedings of the International Astronomical Union, 2005
Chandra images of the elliptical galaxy NGC 4261 have revealed an anisotropy in the spatial distr... more Chandra images of the elliptical galaxy NGC 4261 have revealed an anisotropy in the spatial distribution of the off-nuclear X-ray sources, interpreted by Zezas et al. as evidence of an association with a young stellar population. Our independent analysis of archive X-ray (Chandra) and optical (INT and HST) observations confirms the anisotropy of the X-ray sources but conducts to a different interpretation for their origin. We find that nearly half of the X-ray sources are associated to a globular cluster (optical counterpart) suggesting that they are accreting low-mass X-ray binaries. Where color index information is available, the X-ray sources are found to reside in red (metal-rich) systems. The luminosity function of the X-ray sources is also consistent with the one drawn from a population of Low Mass X-ray Binaries. We further investigate the properties of the sample of point-like sources obtained from archival optical images that we suggest are good globular cluster candidates and for which we find that the projected spatial distribution is non-homogeneous. In addition, we show that the distributions of the optical and X-ray populations are very similar, which leads us to conclude that the spatial anisotropy of the X-ray sources in NGC 4261 is mostly a reflection of the anisotropy of the globular cluster population.
Chandra images of the elliptical galaxy NGC 4261 have revealed an anisotropy in the spatial distr... more Chandra images of the elliptical galaxy NGC 4261 have revealed an anisotropy in the spatial distribution of the off-nuclear X-ray sources, interpreted by Zezas et al. as evidence of an association with a young stellar population. Our independent analysis of archive X-ray (Chandra) and optical (INT and HST) observations confirms the anisotropy of the X-ray sources but conducts to a different interpretation for their origin. We find that nearly half of the X-ray sources are associated to a globular cluster (optical counterpart) suggesting that they are accreting low-mass X-ray binaries. Where color index information is available, the X-ray sources are found to reside in red (metal-rich) systems. The luminosity function of the X-ray sources is also consistent with the one drawn from a population of Low Mass X-ray Binaries. We further investigate the properties of the sample of point-like sources obtained from archival optical images that we suggest are good globular cluster candidates and for which we find that the projected spatial distribution is non-homogeneous. In addition, we show that the distributions of the optical and X-ray populations are very similar, which leads us to conclude that the spatial anisotropy of the X-ray sources in NGC 4261 is mostly a reflection of the anisotropy of the globular cluster population.
By ab initio calculations, we show that when two H vacancies occupy neighboring fcc sites on a hy... more By ab initio calculations, we show that when two H vacancies occupy neighboring fcc sites on a hydrogen-covered Pd(1 1 1) surface, a very low-barrier process exists, leading to a fast effective rotation of the divacancy. As a consequence, divacancies are likely to display a three lobed shape in typical STM images, as reported in a recent experimental work [T. Mitsui, M.K. Rose, E. Fomin, D.F. Ogletree, M. Salmeron, Nature 422 ]. Our results allow for a better understanding of the experimental data, in showing the atomic-scale path responsible for the rotation and in providing a theoretical estimate of the activation energy of the process.
We calculate optical properties from several aerosol models using same assumptions. We test choic... more We calculate optical properties from several aerosol models using same assumptions. We test choices on mixing state, refractive index, density and hygroscopicity. The most sensitive parameter is the aerosol mixing state. The related uncertainty on calculated AOD and SSA is 30e35%.
The Air Quality Model Evaluation International Initiative (AQMEII) has now reached its second pha... more The Air Quality Model Evaluation International Initiative (AQMEII) has now reached its second phase which is dedicated to the evaluation of online coupled chemistry-meteorology models. Sixteen modelling groups from Europe and five from North America have run regional air quality models to simulate the year 2010 over one European and one North American domain. The MACC re-analysis has been used as chemical initial (IC) and boundary conditions (BC) by all participating regional models in AQMEII-2. The aim of the present work is to evaluate the MACC re-analysis along with the participating regional models against a set of ground-based measurements (O 3 , CO, NO, NO 2 , SO 2 , SO 4 2-) and vertical profiles (O 3 and CO). Results indicate different degrees of agreement between the measurements and the MACC re-analysis, with an overall better performance over the North American domain. The influence of BC on regional air quality simulations is analyzed in a qualitative way by contrasting model performance for the MACC re-analysis with that for the regional models. This approach complements more quantitative approaches documented in the literature that often have involved sensitivity simulations but typically were limited to only one or only a few regional scale models. Results suggest an important influence of the BC on ozone for which the underestimation in winter in the MACC re-analysis is mimicked by the regional models. For CO, it is found that background concentrations near the domain boundaries are rather close to observations while those over the interior of the two continents are underpredicted by both MACC and the regional models over Europe but only by MACC over North America. This indicates that emission differences between the MACC re-analysis and the regional models can have a profound impact on model performance and points to the need for harmonization of inputs in future linked global/regional modeling studies.
Comparative analysis of meteorological performance of coupled chemistry-meteorology models in the... more Comparative analysis of meteorological performance of coupled chemistry-meteorology models in the context of AQMEII phase 2, Atmospheric Environment (2015), Abstract 53 Air pollution simulations critically depend on the quality of the underlying meteorology. In 54 phase 2 of the Air Quality Model Evaluation International Initiative (AQMEII-2), thirteen 55 modeling groups from Europe and four groups from North America operating eight 56 different regional coupled chemistry and meteorology models participated in a coordinated 57 model evaluation exercise. Each group simulated the year 2010 for a domain covering 58 either Europe or North America or both. Here were present an operational analysis of 59 model performance with respect to key meteorological variables relevant for atmospheric 60 chemistry processes and air quality. These parameters include temperature and wind speed 61 at the surface and in the vertical profile, incoming solar radiation at the ground, 62 precipitation, and planetary boundary layer heights. A similar analysis was performed 63 during AQMEII phase 1 (Vautard et al., 2012) for offline air quality models not directly 64 coupled to the meteorological model core as the model systems investigated here. Similar 65 to phase 1, we found significant overpredictions of 10-m wind speeds by most models, 66 more pronounced during night than during daytime. The seasonal evolution of temperature 67 was well captured with monthly mean biases below 2 K over all domains. Solar incoming 68 radiation, precipitation and PBL heights, on the other hand, showed significant spread 69 between models and observations suggesting that major challenges still remain in the 70 simulation of meteorological parameters relevant for air quality and for chemistry -71 climate interactions at the regional scale.
The formulations of tropospheric gas-phase chemistry ("mechanisms") anuscript lick here to downlo... more The formulations of tropospheric gas-phase chemistry ("mechanisms") anuscript lick here to download Manuscript: knote_et_al_manuscript_20141127.tex Click here to view linked References 157 2.5. Emissions 158 We test the mechanisms under a realistic range of emission conditions. 159 Therefore, we employ the exact emission input (2-D time-varying fields of 160 12
The simultaneous, diffusion-controlled growth of GdFeO3 (perovskite) and Gd3Fe5O12 (garnet) was s... more The simultaneous, diffusion-controlled growth of GdFeO3 (perovskite) and Gd3Fe5O12 (garnet) was studied at 1200–1400 °C in Gd2O3–Fe2O3 diffusion couples. Both compounds were found to grow as parallel layers according to the parabolic rate law. The parabolic rate constants of the second kind for the exclusive growth of each compound (k1II for GdFeO3, k2II for Gd3Fe5O12) were calculated from the experimentally
Monthly Notices of the Royal Astronomical Society, 2007
Chandra and XM M −N ewton observations of the Cartwheel galaxy show ∼ 17 bright X-ray sources ( >... more Chandra and XM M −N ewton observations of the Cartwheel galaxy show ∼ 17 bright X-ray sources ( > ∼ 5 × 10 38 erg s −1 ), all within the gas-rich outer ring. We explore the hypothesis that these X-ray sources are powered by intermediate-mass black holes (IMBHs) accreting gas or undergoing mass transfer from a stellar companion. To this purpose, we run N -body/SPH simulations of the galaxy interaction which might have led to the formation of Cartwheel, tracking the dynamical evolution of two different IMBH populations: halo and disc IMBHs. Halo IMBHs cannot account for the observed X-ray sources, as only a few of them cross the outer ring. Instead, more than half of the disc IMBHs are pulled in the outer ring as a consequence of the galaxy collision. However, also in the case of disc IMBHs, accretion from surrounding gas clouds cannot account for the high luminosities of the observed sources. Finally, more than 500 disc IMBHs are required to produce < ∼ 15 X-ray sources via mass transfer from very young stellar companions. Such number of IMBHs is very large and implies extreme assumptions. Thus, the hypothesis that all the observed X-ray sources in Cartwheel are associated with IMBHs is hardly consistent with our simulations, even if it is still possible that IMBHs account for the few ( < ∼ 1 − 5) brightest ultraluminous X-ray sources (ULXs).
We detect ionized gas characteristics indicative of winds in three disk-dominated galaxies that a... more We detect ionized gas characteristics indicative of winds in three disk-dominated galaxies that are members of a super-group at z = 0.37 that will merge to form a Coma-mass cluster. All three galaxies are IR-luminous (L IR > 4 × 10 10 L ⊙ , SFR > 8 M ⊙ yr −1 ) and lie outside the X-ray cores of the galaxy groups. We find that the most IR-luminous galaxy has strong blue and redshifted emission lines with velocities of ∼ ±200 km s −1 and a third, blueshifted (∼ 900 km s −1 ) component. This galaxy's line-widths (Hβ, [OIII]λ5007, [NII], Hα) correspond to velocities of 100 − 1000 km s −1 . We detect extraplanar gas in two of three galaxies with SFR > 8 M ⊙ yr −1 whose orientations are approximately edge-on and which have IFU spaxels off the stellar disk. IFU maps reveal that the extraplanar gas extends to r h ∼ 10 kpc; [NII] and Hα line-widths correspond to velocities of ∼ 200 − 400 km s −1 in the disk and decrease to ∼ 50 − 150 km s −1 above the disk. Multi-wavelength observations indicate that the emission is dominated by star formation. Including the most IR-luminous galaxy we find that 18% of supergroup members with SFR > 8 M ⊙ yr −1 show ionized gas characteristics indicative of outflows. This is a lower limit as showing that gas is outflowing in the remaining, moderately inclined, galaxies requires a non-trivial decoupling of contributions to the emission lines from rotational and turbulent motion. Ionized gas mass loss in these winds is ∼ 0.1 M ⊙ yr −1 for each galaxy, although the winds are likely to entrain significantly larger amounts of mass in neutral and molecular gas.
We investigate possible environmental and morphological trends in the z ∼ 0 bar fraction using tw... more We investigate possible environmental and morphological trends in the z ∼ 0 bar fraction using two carefully selected samples representative of a low-density environment (the isolated galaxies from the AMIGA sample) and of a dense environment (galaxies in the Virgo cluster). Galaxies span a stellar mass range from 10 8 to 10 12 M and are visually classified using both high-resolution NIR (H-band) imaging and optical rgb images. We find that the bar fraction in disk galaxies is independent of environment suggesting that bar formation may occur prior to the formation of galaxy clusters. The bar fraction in early type spirals (Sa − Sb) is ∼50%, which is twice as high as the late type spirals (Sbc − Sm). The higher bar fraction in early type spirals may be due to the fact that a significant fraction of their bulges are pseudo-bulges which form via the buckling instability of a bar. i.e. a large part of the Hubble sequence is due to secular processes which move disc galaxies from late to early types. There is a hint of a higher bar fraction with higher stellar masses which may be due to the susceptibility to bar instabilities as the baryon fractions increase in halos of larger masses. Overall, the S0 population has a lower bar fraction than the Sa − Sb galaxies and their barred fraction drops significantly with decreasing stellar mass. This supports the notion that S0s form via the transformation of disk galaxies that enter the cluster environment. The gravitational harassment thickens the stellar disks, wiping out spiral patterns and eventually erasing the bar -a process that is more effective at lower galaxy masses.
Giant low surface brightness galaxies (GLSBs) have flat discs extending up to ∼ 100 kpc. Their fo... more Giant low surface brightness galaxies (GLSBs) have flat discs extending up to ∼ 100 kpc. Their formation is a puzzle for cosmological simulations in the cold dark matter scenario. We suggest that GLSBs might be the final product of the evolution of collisional ring galaxies. In fact, our simulations show that, approximately 0.5 − 1.5 Gyr after the collision which led to the formation of the ring galaxy, the ring keeps expanding and fades, while the disc becomes very large (∼ 100 kpc) and flat. At this stage, our simulated galaxies match many properties of GLSBs (surface brightness profile, morphology, HI spectrum and rotation curve).
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Papers by Lea Giordano