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Abstract: We use the recent measurement of the velocity dispersion of star-forming,outer-disk knots by Herbert-Fort et al. in the nearly face-on galaxy NGC 628,in combination with other data from the literature, to execute astraightforward test of gravity at low accelerations. Specifically, therotation curve at large radius sets the degree of non-standard acceleration andthen the predicted scaleheight of the knots at that radius provides the test ofthe scenario. For our demonstration, we presume that the H alpha knots, whichare young age < 10 Myr, are distributed like the gas from which they haverecently formed and find a marginal > 97% confidence discrepancy with amodified gravity scenario given the current data. More interestingly, wedemonstrate that there is no inherent limitation that prevents such a test fromreaching possible discrimination at the > 4 sigma level with a reasonableinvestment of observational resources.



Autor: Dennis Zaritsky, Dimitrios Psaltis U. Arizona

Fuente: https://arxiv.org/







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