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Papers by Omima Osman Mohammed Osman

Galaxy-wide star formation can be quenched by a number of physical processes such as environmenta... more Galaxy-wide star formation can be quenched by a number of physical processes such as environmental effects (e.g., ram pressure stripping) and supernova feedback. Using numerical simulations, we here demonstrate that star formation can be severely suppressed in disk galaxies with their gas disks counter-rotating with respect to their stellar disks. This new mechanism of star formation suppression (or quenching) does not depend so strongly on model parameters of disk galaxies, such as bulge-to-disk- ratios and gas mass fractions. Such severe suppression of star formation is due largely to the suppression of the gas density enhancing mechanism i.e spiral arm formation in disk galaxies with counter-rotating gas. Our simulations also show that molecular hydrogen and dust can be rather slowly consumed by star formation in disk galaxies with counter-rotating gas disks (i.e., long gas depletion timescale). Based on these results, we suggest that spiral and S0 galaxies with counter-rotation ...

Monthly Notices of the Royal Astronomical Society, 2020

Photoelectric heating (PEH) influences the temperature and density of the interstellar medium (IS... more Photoelectric heating (PEH) influences the temperature and density of the interstellar medium (ISM), potentially also affecting star formation. PEH is expected to have a stronger effect on massive galaxies, as they host larger dust reservoirs compared to dwarf systems. Accordingly, in this paper, we study PEH effects in Milky Way-like galaxies using a smoothed particle hydrodynamics code, which self-consistently implements the evolution of the gas, dust, and interstellar radiation field. Dust evolution includes dust formation by stars, destruction by SNe, and growth in dense media. We find that PEH suppresses star formation due to the excess heating that reduces the ISM density. This suppression is seen across the entire range of gas fractions, star-formation recipes, dust models, and PEH efficiencies investigated by our code. The suppression ranges from negligible values to approximately a factor of five depending on the specific implementation. Galaxy models having higher gas frac...

Monthly Notices of the Royal Astronomical Society: Letters, 2017

Galaxy-wide star formation can be quenched by a number of physical processes such as environmenta... more Galaxy-wide star formation can be quenched by a number of physical processes such as environmental effects (e.g., ram pressure stripping) and supernova feedback. Using numerical simulations, we here demonstrate that star formation can be severely suppressed in disk galaxies with their gas disks counter-rotating with respect to their stellar disks. This new mechanism of star formation suppression (or quenching) does not depend so strongly on model parameters of disk galaxies, such as bulge-to-diskratios and gas mass fractions. Such severe suppression of star formation is due largely to the suppression of the gas density enhancing mechanism i.e spiral arm formation in disk galaxies with counter-rotating gas. Our simulations also show that molecular hydrogen and dust can be rather slowly consumed by star formation in disk galaxies with counter-rotating gas disks (i.e., long gas depletion timescale). Based on these results, we suggest that spiral and S0 galaxies with counter-rotation can have rather low star formation rate for their gas densities. Also we suggest that a minor fraction of S0 galaxies have no prominent spiral arms, because they have a higher fraction of counter-rotating gas. We predict that poststarburst 'E+A' disk galaxies with cold gas could have counter-rotating gas.

Monthly Notices of the Royal Astronomical Society, 2020

We use Milky Way-like chemodynamical simulations with a new treatment for dust destruction and gr... more We use Milky Way-like chemodynamical simulations with a new treatment for dust destruction and growth to investigate how these two processes affect the properties of the interstellar medium in galaxies. We focus on the role of two specific parameters, namely fdes (a new parameter that determines the fraction of dust destroyed in a single gas particle vicinity of a supernova) and Cs (the probability that a metal atom or ion sticks to the dust grain after colliding, i.e. the sticking coefficient), in regulating the amount and distribution of dust, cold gas and metals in galaxies. We find that simulated galaxies with low fdes and/or high Cs values not only produce more dust, but they also have a shallower correlation between the dust surface density and the total gas surface density, and a steeper correlation between the dust-to-gas ratio and the metallicity. Only for values of fdes between 0.01 and 0.02, and of Cs between 0.5 and 1 do our simulations produce an average slope of the du...

Galaxy-wide star formation can be quenched by a number of physical processes such as environmenta... more Galaxy-wide star formation can be quenched by a number of physical processes such as environmental effects (e.g., ram pressure stripping) and supernova feedback. Using numerical simulations, we here demonstrate that star formation can be severely suppressed in disk galaxies with their gas disks counter-rotating with respect to their stellar disks. This new mechanism of star formation suppression (or quenching) does not depend so strongly on model parameters of disk galaxies, such as bulge-to-disk- ratios and gas mass fractions. Such severe suppression of star formation is due largely to the suppression of the gas density enhancing mechanism i.e spiral arm formation in disk galaxies with counter-rotating gas. Our simulations also show that molecular hydrogen and dust can be rather slowly consumed by star formation in disk galaxies with counter-rotating gas disks (i.e., long gas depletion timescale). Based on these results, we suggest that spiral and S0 galaxies with counter-rotation ...

Monthly Notices of the Royal Astronomical Society, 2020

Photoelectric heating (PEH) influences the temperature and density of the interstellar medium (IS... more Photoelectric heating (PEH) influences the temperature and density of the interstellar medium (ISM), potentially also affecting star formation. PEH is expected to have a stronger effect on massive galaxies, as they host larger dust reservoirs compared to dwarf systems. Accordingly, in this paper, we study PEH effects in Milky Way-like galaxies using a smoothed particle hydrodynamics code, which self-consistently implements the evolution of the gas, dust, and interstellar radiation field. Dust evolution includes dust formation by stars, destruction by SNe, and growth in dense media. We find that PEH suppresses star formation due to the excess heating that reduces the ISM density. This suppression is seen across the entire range of gas fractions, star-formation recipes, dust models, and PEH efficiencies investigated by our code. The suppression ranges from negligible values to approximately a factor of five depending on the specific implementation. Galaxy models having higher gas frac...

Monthly Notices of the Royal Astronomical Society: Letters, 2017

Galaxy-wide star formation can be quenched by a number of physical processes such as environmenta... more Galaxy-wide star formation can be quenched by a number of physical processes such as environmental effects (e.g., ram pressure stripping) and supernova feedback. Using numerical simulations, we here demonstrate that star formation can be severely suppressed in disk galaxies with their gas disks counter-rotating with respect to their stellar disks. This new mechanism of star formation suppression (or quenching) does not depend so strongly on model parameters of disk galaxies, such as bulge-to-diskratios and gas mass fractions. Such severe suppression of star formation is due largely to the suppression of the gas density enhancing mechanism i.e spiral arm formation in disk galaxies with counter-rotating gas. Our simulations also show that molecular hydrogen and dust can be rather slowly consumed by star formation in disk galaxies with counter-rotating gas disks (i.e., long gas depletion timescale). Based on these results, we suggest that spiral and S0 galaxies with counter-rotation can have rather low star formation rate for their gas densities. Also we suggest that a minor fraction of S0 galaxies have no prominent spiral arms, because they have a higher fraction of counter-rotating gas. We predict that poststarburst 'E+A' disk galaxies with cold gas could have counter-rotating gas.

Monthly Notices of the Royal Astronomical Society, 2020

We use Milky Way-like chemodynamical simulations with a new treatment for dust destruction and gr... more We use Milky Way-like chemodynamical simulations with a new treatment for dust destruction and growth to investigate how these two processes affect the properties of the interstellar medium in galaxies. We focus on the role of two specific parameters, namely fdes (a new parameter that determines the fraction of dust destroyed in a single gas particle vicinity of a supernova) and Cs (the probability that a metal atom or ion sticks to the dust grain after colliding, i.e. the sticking coefficient), in regulating the amount and distribution of dust, cold gas and metals in galaxies. We find that simulated galaxies with low fdes and/or high Cs values not only produce more dust, but they also have a shallower correlation between the dust surface density and the total gas surface density, and a steeper correlation between the dust-to-gas ratio and the metallicity. Only for values of fdes between 0.01 and 0.02, and of Cs between 0.5 and 1 do our simulations produce an average slope of the du...