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DTSTART;TZID=Europe/Rome:20190219T114500
DTEND;TZID=Europe/Rome:20190219T124500
DTSTAMP:20260418T062046
CREATED:20180907T101417Z
LAST-MODIFIED:20180907T101417Z
UID:4371-1550576700-1550580300@www.oa-roma.inaf.it
SUMMARY:colloquium - Guido De Marchi
DESCRIPTION:
URL:https://www.oa-roma.inaf.it/event/colloquium-by-guido-de-marchi/
LOCATION:Aula Gratton
CATEGORIES:Seminari
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Rome:20190219T114500
DTEND;TZID=Europe/Rome:20190219T124500
DTSTAMP:20260418T062046
CREATED:20180907T101417Z
LAST-MODIFIED:20190118T055424Z
UID:4767-1550576700-1550580300@www.oa-roma.inaf.it
SUMMARY:Star formation in the Local Group
DESCRIPTION:Using Hubble Space Telescope (HST) observations\, we have identified and\ncharacterised almost 50\,000 pre-main sequence (PMS) stars in several\nstar-forming regions in the Milky Way and Magellanic Clouds. These objects\nare still undergoing active mass accretion\, as revealed by excess emission\nin the Halpha band. Detailed knowledge of the extinction law in these\nfields\, which we derive directly from the observations\, allows us to\naccurately obtain stellar physical parameters (temperature\, luminosity\,\nage\, mass\, and mass accretion rate). This is presently the largest and\nmost homogeneous sample of PMS objects\, on which we are conducting the\nfirst comprehensive and systematic study of the PMS phase\, spanning a wide\nrange of masses (0.5-4 Msun)\, metallicities (0.1-1 Zsun) and ages (0.5-30\nMyr). \nI will discuss how star formation has proceeded in these regions over\nmultiple recent bursts and how the accretion process depends on the\nphysical properties of the individual stars and of the environment. We\nhave discovered an important dependence of the mass accretion rate on\nmetallicity: mass accretion rates for stars of the same mass and age are\nsystematically higher in the Magellanic Clouds than in the Milky Way and\nare expected to have been equally high at redshift z~2\, when star\nformation was at its peak in the Universe. I will also show a surprising\nanti-correlation between the variability and intensity of the Halpha\nexcess: this suggests a discrete and clumpy nature for the accretion\nprocess and reveals that the characteristic mass of the infalling parcels\nof gas is comparable to that of the moons of giant planets in the solar\nsystem. \nTo close\, I will illustrate how we plan to thoroughly verify these results\nspectroscopically and to extend them to lower mass objects and to more\nextinguished environments through already planned guaranteed-time\nobservations with the James Webb Space Telescope. Our measurements will\nprovide\, for the first time\, quantitative information on the nature\,\nexcitation\, and kinematics of the infalling gas in these dense environments.
URL:https://www.oa-roma.inaf.it/event/colloquium-by-guido-de-marchi-2/
LOCATION:Aula Gratton
CATEGORIES:Seminari
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