{"id":137,"date":"2018-05-30T06:53:33","date_gmt":"2018-05-30T06:53:33","guid":{"rendered":"http:\/\/www.issibern.ch\/teams\/chemabundism\/?page_id=2"},"modified":"2018-05-30T06:53:33","modified_gmt":"2018-05-30T06:53:33","slug":"sample-page","status":"publish","type":"page","link":"https:\/\/www.issibern.ch\/teams\/chemabundism\/","title":{"rendered":"Abstract"},"content":{"rendered":"

For three decades it has been speculated that the stellar initial mass function (IMF)\u00a0is more biased towards massive stars in starburst environments, especially in massive\u00a0galaxies at high-redshift, which could explain the overabundance of magnesium (mostly\u00a0synthesised in high-mass stars) with respect to iron (mostly produced by type Ia supernovae\u00a0with relatively low-mass progenitors) observed in local elliptical galaxies. However,\u00a0differences in star-formation time scales and\/or the presence of selective galactic outflows\u00a0could act in a similar way. More recently, the so-called\u00a0integrated galaxy-wide IMF (IGIMF) theory has been developed, according to\u00a0which the galaxy-wide IMF lacks massive stars in lower-mass star-forming systems, and\u00a0privileges high-mass star formation in higher-mass systems. This is also evident from\u00a0broadband photometric and H\u03b1 emission studies of thousands of star forming galaxies. According to the theory\u00a0and cosmological simulations, the most extreme IMF variations should be seen in large\u00a0galaxies that shine at high redshifts, where they experience the most powerful starbursts that\u00a0the Universe ever saw, with star formation rates possibly in excess of 500\u20131000 M\u2299<\/sub>\/yr.\u00a0Classical methods of IMF determination, limited at optical, UV, and near-IR wavelengths,\u00a0cannot probe such \u2018monsters\u2019 because of the dust obscuration of stellar light. On the other\u00a0hand, element and isotopic abundances measured in the interstellar medium (ISM) at\u00a0millimeter\/submillimeter wavelengths provide fundamental new constraints for the stellar IMF\u00a0in these extreme objects.<\/span><\/p>\n

In previous work, we have demonstrated that the isotopic ratios of CNO elements, in\u00a0particular the 13<\/sup>C-to-18<\/sup>O ratio measured from the optically thin 13<\/sup>CO and C18<\/sup>O lines in\u00a0molecular gas, are indeed excellent IMF probes for galaxies. This opens up a new window to\u00a0deduce the stellar IMF in dust-shrouded galaxies using ALMA, especially for submillimeter\u00a0galaxies at redshift z<\/em>~1\u20137 that are heavily obscured in the optical. We find a clear boost of the\u00a018<\/sup>O-to-13<\/sup>C ratio in all starburst galaxies, and a top-heavy IMF appears to be the only\u00a0reasonable explanation. Yet, significant uncertainties are still present, when we want to extend this line of\u00a0inquiry to other isotopic abundances (e.g., those of N, Si, and S), to better constrain the IMF\u00a0slopes using their synergy, and to measure isotopic abundances using fine-structure atomic\u00a0lines, ionised lines, and high-lying molecular lines using space telescopes, such as SOFIA,\u00a0Herschel, JWST, and SPICA.<\/span><\/p>\n

With this proposal, we aim at building up an international team whose members have all the\u00a0necessary expertise to (i) reduce significantly the uncertainties present in abundance\u00a0measurements, (ii) extend the measurements to different types of galaxies, from dwarfs to\u00a0ellipticals, at both high and low redshifts, (iii) improve \u2013or develop from scratch\u2013 the\u00a0theoretical tools that are necessary for a full exploitation and interpretation of the data. Our\u00a0team is composed of ten scientists from five European countries and from China. It includes\u00a0experts in numerical simulations, semi-analytical models of galaxy formation in a\u00a0cosmological context, state-of-the-art hydro-dynamical simulations, stellar evolution and\u00a0nucleosynthesis, chemical evolution, IGIMF theory, as well as experts in ISM physics,\u00a0molecular line observations and data analysis. Because of the team composition, and to help\u00a0self-supported external experts from both European countries and China to attend the\u00a0meetings, our team would benefit from one 5-day meeting in ISSI, Bern, and one 5-day\u00a0meeting in ISSI-BJ, Beijing.<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"

For three decades it has been speculated that the stellar initial mass function (IMF)\u00a0is more biased towards massive stars in starburst environments, especially in massive\u00a0galaxies at high-redshift, which could explain the overabundance of magnesium (mostly\u00a0synthesised in high-mass stars) with respect … Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-137","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.issibern.ch\/teams\/chemabundism\/wp-json\/wp\/v2\/pages\/137","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.issibern.ch\/teams\/chemabundism\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.issibern.ch\/teams\/chemabundism\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/www.issibern.ch\/teams\/chemabundism\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.issibern.ch\/teams\/chemabundism\/wp-json\/wp\/v2\/comments?post=137"}],"version-history":[{"count":0,"href":"https:\/\/www.issibern.ch\/teams\/chemabundism\/wp-json\/wp\/v2\/pages\/137\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.issibern.ch\/teams\/chemabundism\/wp-json\/wp\/v2\/media?parent=137"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}