A numerical study is presented of fragmentation in its simplest possible form: that of elongated,... more A numerical study is presented of fragmentation in its simplest possible form: that of elongated, isothermal, axially symmetric clouds. Results have been obtained for different ratios of length to diameter, L/D, and initial Jeans numbers, J0 (ratio of gravitational to thermal energies). Initial density perturbations are introduced on the axis of otherwise uniformly dense cylinders, and the maximum number of
A numerical study of the fragmentation of elongated polytropic axially symmetric clouds is presen... more A numerical study of the fragmentation of elongated polytropic axially symmetric clouds is presented. Results are obtained for various ratios of length to diameter L/D, polytropic constant gamma, and initial Jeans number J0. Initial density perturbations on the axis of otherwise uniformly dense cylinders are introduced, and the maximum number of fragments Nf(max) that can form and grow for combinations
A numerical study is presented of fragmentation in its simplest possible form: that of elongated,... more A numerical study is presented of fragmentation in its simplest possible form: that of elongated, isothermal, axially symmetric clouds. Results have been obtained for different ratios of length to diameter, L/D, and initial Jeans numbers, J0 (ratio of gravitational to thermal energies). Initial density perturbations are introduced on the axis of otherwise uniformly dense cylinders, and the maximum number of
Spectral data cubes of the interacting pair of galaxies NGC 2535 and NGC 2536 (the Arp 82 system)... more Spectral data cubes of the interacting pair of galaxies NGC 2535 and NGC 2536 (the Arp 82 system) targeting bright emission lines in the visible band, obtained with the imaging Fourier transform spectrometer (iFTS) SITELLE attached to the Canada–France–Hawaii Telescope (CFHT), are presented. Analysis of H$\alpha $ velocity maps reveals a bar in $\rm NGC\, 2536$. In $\rm NGC\, 2535$, we find strong non-circular motions outside the ocular ring, in the elliptical arc and tidal tails of $\rm NGC\, 2535$, and a misalignment between the kinematic and photometric position angles. We detect 155 H ii region complexes in the interacting pair of galaxies and determine oxygen abundances for 66 of them using different calibrators. We find, regardless of the indicator used, that the oxygen abundance distribution in $\rm NGC\, 2536$ is shallow, whereas in $\rm NGC\, 2535$, it is best fitted by two slopes, the break occurring beyond the ocular ring. The inner slope is comparable to the one observed...
Monthly Notices of the Royal Astronomical Society, 2019
SIGNALS, the Star formation, Ionized Gas, and Nebular Abundances Legacy Survey, is a large observ... more SIGNALS, the Star formation, Ionized Gas, and Nebular Abundances Legacy Survey, is a large observing programme designed to investigate massive star formation and H ii regions in a sample of local extended galaxies. The programme will use the imaging Fourier transform spectrograph SITELLE at the Canada–France–Hawaii Telescope. Over 355 h (54.7 nights) have been allocated beginning in fall 2018 for eight consecutive semesters. Once completed, SIGNALS will provide a statistically reliable laboratory to investigate massive star formation, including over 50 000 resolved H ii regions: the largest, most complete, and homogeneous data base of spectroscopically and spatially resolved extragalactic H ii regions ever assembled. For each field observed, three datacubes covering the spectral bands of the filters SN1 (363–386 nm), SN2 (482–513 nm), and SN3 (647–685 nm) are gathered. The spectral resolution selected for each spectral band is 1000, 1000, and 5000, respectively. As defined, the proj...
Galaxies usually follow a mass–metallicity relation, where higher mass galaxies are typically mor... more Galaxies usually follow a mass–metallicity relation, where higher mass galaxies are typically more metal-rich than lower mass galaxies. Yet, tidal dwarf galaxies are outliers to this relation. These kinds of dwarfs are formed in galactic mergers. Since their material comes from the parent galaxies, they are typically more metal-rich than regular dwarfs. However, galaxies were far less enriched when the Universe was younger. One can ask if tidal dwarfs that formed at high redshift could be chemically distinguished from regular dwarfs. To answer this question, we performed a series of numerical simulations of gas-rich galaxy mergers at high redshift. We then identified the dwarf galaxies that formed in these mergers, and studied the evolution of their metal content. While the initial abundance of metals in the progenitors was low, the merger allows rapid enrichment and all tidal dwarf galaxies end up with high abundances. Their mass–metallicity relation is well fitted by the relation ...
The main goal of this paper is to compare the relative importance of destruction by tides, vs. de... more The main goal of this paper is to compare the relative importance of destruction by tides, vs. destruction by mergers, in order to assess if tidal destruction of dwarf galaxies in clusters is a viable scenario for explaining the origin of intracluster stars. We have designed a simple algorithm for simulating the evolution of isolated clusters. The distribution of galaxies in the cluster is evolved using a direct gravitational N-body algorithm combined with a subgrid treatment of physical processes such as mergers, tidal disruption, and galaxy harassment. Using this algorithm, we have performed a total of 227 simulations. Our main results are (1) destruction of dwarf galaxies by mergers dominates over destruction by tides, and (2) the destruction of dwarf galaxies by tides is sufficient to explain the observed intracluster light in clusters.
We simulate anisotropic outflows of AGN, and investigate the large-scale impact of the cosmologic... more We simulate anisotropic outflows of AGN, and investigate the large-scale impact of the cosmological population of AGN outflows over the Hubbl e time by performing NbodyΛCDM simulations. Using the observed quasar luminosity func tio to get the redshift and luminosity distribution, and analytical models for the outflow expansion, AGNs are allowed to evolve in a cosmological volume. By the present ep och, 13− 25% of the total volume is found to be pervaded by AGN outflows, with 10 −9 G magnetic field.
Galactic outflows play a major role in the evolution of galaxies and the intergalactic medium (IG... more Galactic outflows play a major role in the evolution of galaxies and the intergalactic medium (IGM). The energy deposited into the interstellar medium by supernovae and active galactic nuclei can accelerate the gas past the escape velocity, and eject it into the IGM. This will affect the subsequent evolution of the galaxy, by reducing or eliminating star formation, and quenching the accretion of matter onto the central AGN. Galactic outflows is the main process by which energy and processed interstellar matter is transported into the IGM. This affects the subsequent formation of other galaxies. The energy carried by outflows can strip protogalactic halos of their gas, preventing galaxies from forming. Conversely, the metals carried by outflows can modify the composition and cooling rates of the gas in protogalactic halos, favoring the formation of galaxies. In this paper, I review the various techniques used to simulate galactic outflows and their impact on galaxy and IGM evolution.
A numerical study is presented of fragmentation in its simplest possible form: that of elongated,... more A numerical study is presented of fragmentation in its simplest possible form: that of elongated, isothermal, axially symmetric clouds. Results have been obtained for different ratios of length to diameter, L/D, and initial Jeans numbers, J0 (ratio of gravitational to thermal energies). Initial density perturbations are introduced on the axis of otherwise uniformly dense cylinders, and the maximum number of
A numerical study of the fragmentation of elongated polytropic axially symmetric clouds is presen... more A numerical study of the fragmentation of elongated polytropic axially symmetric clouds is presented. Results are obtained for various ratios of length to diameter L/D, polytropic constant gamma, and initial Jeans number J0. Initial density perturbations on the axis of otherwise uniformly dense cylinders are introduced, and the maximum number of fragments Nf(max) that can form and grow for combinations
A numerical study is presented of fragmentation in its simplest possible form: that of elongated,... more A numerical study is presented of fragmentation in its simplest possible form: that of elongated, isothermal, axially symmetric clouds. Results have been obtained for different ratios of length to diameter, L/D, and initial Jeans numbers, J0 (ratio of gravitational to thermal energies). Initial density perturbations are introduced on the axis of otherwise uniformly dense cylinders, and the maximum number of
Spectral data cubes of the interacting pair of galaxies NGC 2535 and NGC 2536 (the Arp 82 system)... more Spectral data cubes of the interacting pair of galaxies NGC 2535 and NGC 2536 (the Arp 82 system) targeting bright emission lines in the visible band, obtained with the imaging Fourier transform spectrometer (iFTS) SITELLE attached to the Canada–France–Hawaii Telescope (CFHT), are presented. Analysis of H$\alpha $ velocity maps reveals a bar in $\rm NGC\, 2536$. In $\rm NGC\, 2535$, we find strong non-circular motions outside the ocular ring, in the elliptical arc and tidal tails of $\rm NGC\, 2535$, and a misalignment between the kinematic and photometric position angles. We detect 155 H ii region complexes in the interacting pair of galaxies and determine oxygen abundances for 66 of them using different calibrators. We find, regardless of the indicator used, that the oxygen abundance distribution in $\rm NGC\, 2536$ is shallow, whereas in $\rm NGC\, 2535$, it is best fitted by two slopes, the break occurring beyond the ocular ring. The inner slope is comparable to the one observed...
Monthly Notices of the Royal Astronomical Society, 2019
SIGNALS, the Star formation, Ionized Gas, and Nebular Abundances Legacy Survey, is a large observ... more SIGNALS, the Star formation, Ionized Gas, and Nebular Abundances Legacy Survey, is a large observing programme designed to investigate massive star formation and H ii regions in a sample of local extended galaxies. The programme will use the imaging Fourier transform spectrograph SITELLE at the Canada–France–Hawaii Telescope. Over 355 h (54.7 nights) have been allocated beginning in fall 2018 for eight consecutive semesters. Once completed, SIGNALS will provide a statistically reliable laboratory to investigate massive star formation, including over 50 000 resolved H ii regions: the largest, most complete, and homogeneous data base of spectroscopically and spatially resolved extragalactic H ii regions ever assembled. For each field observed, three datacubes covering the spectral bands of the filters SN1 (363–386 nm), SN2 (482–513 nm), and SN3 (647–685 nm) are gathered. The spectral resolution selected for each spectral band is 1000, 1000, and 5000, respectively. As defined, the proj...
Galaxies usually follow a mass–metallicity relation, where higher mass galaxies are typically mor... more Galaxies usually follow a mass–metallicity relation, where higher mass galaxies are typically more metal-rich than lower mass galaxies. Yet, tidal dwarf galaxies are outliers to this relation. These kinds of dwarfs are formed in galactic mergers. Since their material comes from the parent galaxies, they are typically more metal-rich than regular dwarfs. However, galaxies were far less enriched when the Universe was younger. One can ask if tidal dwarfs that formed at high redshift could be chemically distinguished from regular dwarfs. To answer this question, we performed a series of numerical simulations of gas-rich galaxy mergers at high redshift. We then identified the dwarf galaxies that formed in these mergers, and studied the evolution of their metal content. While the initial abundance of metals in the progenitors was low, the merger allows rapid enrichment and all tidal dwarf galaxies end up with high abundances. Their mass–metallicity relation is well fitted by the relation ...
The main goal of this paper is to compare the relative importance of destruction by tides, vs. de... more The main goal of this paper is to compare the relative importance of destruction by tides, vs. destruction by mergers, in order to assess if tidal destruction of dwarf galaxies in clusters is a viable scenario for explaining the origin of intracluster stars. We have designed a simple algorithm for simulating the evolution of isolated clusters. The distribution of galaxies in the cluster is evolved using a direct gravitational N-body algorithm combined with a subgrid treatment of physical processes such as mergers, tidal disruption, and galaxy harassment. Using this algorithm, we have performed a total of 227 simulations. Our main results are (1) destruction of dwarf galaxies by mergers dominates over destruction by tides, and (2) the destruction of dwarf galaxies by tides is sufficient to explain the observed intracluster light in clusters.
We simulate anisotropic outflows of AGN, and investigate the large-scale impact of the cosmologic... more We simulate anisotropic outflows of AGN, and investigate the large-scale impact of the cosmological population of AGN outflows over the Hubbl e time by performing NbodyΛCDM simulations. Using the observed quasar luminosity func tio to get the redshift and luminosity distribution, and analytical models for the outflow expansion, AGNs are allowed to evolve in a cosmological volume. By the present ep och, 13− 25% of the total volume is found to be pervaded by AGN outflows, with 10 −9 G magnetic field.
Galactic outflows play a major role in the evolution of galaxies and the intergalactic medium (IG... more Galactic outflows play a major role in the evolution of galaxies and the intergalactic medium (IGM). The energy deposited into the interstellar medium by supernovae and active galactic nuclei can accelerate the gas past the escape velocity, and eject it into the IGM. This will affect the subsequent evolution of the galaxy, by reducing or eliminating star formation, and quenching the accretion of matter onto the central AGN. Galactic outflows is the main process by which energy and processed interstellar matter is transported into the IGM. This affects the subsequent formation of other galaxies. The energy carried by outflows can strip protogalactic halos of their gas, preventing galaxies from forming. Conversely, the metals carried by outflows can modify the composition and cooling rates of the gas in protogalactic halos, favoring the formation of galaxies. In this paper, I review the various techniques used to simulate galactic outflows and their impact on galaxy and IGM evolution.
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Papers by Hugo Martel