Project acronym ASSESS
Project Episodic Mass Loss in the Most Massive Stars: Key to Understanding the Explosive Early Universe
Researcher (PI) Alceste BONANOS
Host Institution (HI) NATIONAL OBSERVATORY OF ATHENS
Call Details Consolidator Grant (CoG), PE9, ERC-2017-COG
Summary Massive stars dominate their surroundings during their short lifetimes, while their explosive deaths impact the chemical evolution and spatial cohesion of their hosts. After birth, their evolution is largely dictated by their ability to remove layers of hydrogen from their envelopes. Multiple lines of evidence are pointing to violent, episodic mass-loss events being responsible for removing a large part of the massive stellar envelope, especially in low-metallicity galaxies. Episodic mass loss, however, is not understood theoretically, neither accounted for in state-of-the-art models of stellar evolution, which has far-reaching consequences for many areas of astronomy. We aim to determine whether episodic mass loss is a dominant process in the evolution of the most massive stars by conducting the first extensive, multi-wavelength survey of evolved massive stars in the nearby Universe. The project hinges on the fact that mass-losing stars form dust and are bright in the mid-infrared. We plan to (i) derive physical parameters of a large sample of dusty, evolved targets and estimate the amount of ejected mass, (ii) constrain evolutionary models, (iii) quantify the duration and frequency of episodic mass loss as a function of metallicity. The approach involves applying machine-learning algorithms to existing multi-band and time-series photometry of luminous sources in ~25 nearby galaxies. Dusty, luminous evolved massive stars will thus be automatically classified and follow-up spectroscopy will be obtained for selected targets. Atmospheric and SED modeling will yield parameters and estimates of time-dependent mass loss for ~1000 luminous stars. The emerging trend for the ubiquity of episodic mass loss, if confirmed, will be key to understanding the explosive early Universe and will have profound consequences for low-metallicity stars, reionization, and the chemical evolution of galaxies.
Summary
Massive stars dominate their surroundings during their short lifetimes, while their explosive deaths impact the chemical evolution and spatial cohesion of their hosts. After birth, their evolution is largely dictated by their ability to remove layers of hydrogen from their envelopes. Multiple lines of evidence are pointing to violent, episodic mass-loss events being responsible for removing a large part of the massive stellar envelope, especially in low-metallicity galaxies. Episodic mass loss, however, is not understood theoretically, neither accounted for in state-of-the-art models of stellar evolution, which has far-reaching consequences for many areas of astronomy. We aim to determine whether episodic mass loss is a dominant process in the evolution of the most massive stars by conducting the first extensive, multi-wavelength survey of evolved massive stars in the nearby Universe. The project hinges on the fact that mass-losing stars form dust and are bright in the mid-infrared. We plan to (i) derive physical parameters of a large sample of dusty, evolved targets and estimate the amount of ejected mass, (ii) constrain evolutionary models, (iii) quantify the duration and frequency of episodic mass loss as a function of metallicity. The approach involves applying machine-learning algorithms to existing multi-band and time-series photometry of luminous sources in ~25 nearby galaxies. Dusty, luminous evolved massive stars will thus be automatically classified and follow-up spectroscopy will be obtained for selected targets. Atmospheric and SED modeling will yield parameters and estimates of time-dependent mass loss for ~1000 luminous stars. The emerging trend for the ubiquity of episodic mass loss, if confirmed, will be key to understanding the explosive early Universe and will have profound consequences for low-metallicity stars, reionization, and the chemical evolution of galaxies.
Max ERC Funding
1 128 750 €
Duration
Start date: 2018-09-01, End date: 2023-08-31
Project acronym PASIPHAE
Project Overcoming the Dominant Foreground of Inflationary B-modes: Tomography of Galactic Magnetic Dust via Measurements of Starlight Polarization
Researcher (PI) Konstantinos TASSIS
Host Institution (HI) IDRYMA TECHNOLOGIAS KAI EREVNAS
Call Details Consolidator Grant (CoG), PE9, ERC-2017-COG
Summary An inflation-probing B-mode signal in the polarization of the cosmic microwave background (CMB) would be a discovery of utmost importance in physics. While such a signal is aggressively pursued by experiments around the world, recent Planck results have showed that this breakthrough is still out of reach, because of contamination from Galactic dust. To get to the primordial B-modes, we need to subtract polarized emission of magnetized interstellar dust with high accuracy. A critical piece of this puzzle is the 3D structure of the magnetic field threading dust clouds, which cannot be accessed through microwave observations alone, since they record integrated emission along the line of sight. Instead, observations of a large number of stars at known distances in optical polarization, tracing the same CMB-obscuring dust, can map the magnetic field between them. The Gaia mission is measuring distances to a billion stars, providing an opportunity to produce, the first-ever tomographic map of the Galactic magnetic field, using optical polarization of starlight. Such a map would not only boost CMB polarization foreground removal, but it would also have a profound impact in a wide range of astrophysical research, including interstellar medium physics, high-energy astrophysics, and galactic evolution. Taking advantage of our privately-funded, novel-technology, high-accuracy WALOP optopolarimeters currently under construction, we propose an ambitious optopolarimetric program of unprecedented scale that can meet this challenge: a survey of both northern and southern Galactic polar regions targeted by CMB experiments, covering >10,000 square degrees, which will measure linear optical polarization at 0.2% accuracy of over 360 stars per square degree (over 3.5M stars, a 1000-fold increase over the state of the art), combining wide-field-optimized instruments and an extraordinary commitment of observing time by Skinakas Observatory and the South African Astronomical Observatory.
Summary
An inflation-probing B-mode signal in the polarization of the cosmic microwave background (CMB) would be a discovery of utmost importance in physics. While such a signal is aggressively pursued by experiments around the world, recent Planck results have showed that this breakthrough is still out of reach, because of contamination from Galactic dust. To get to the primordial B-modes, we need to subtract polarized emission of magnetized interstellar dust with high accuracy. A critical piece of this puzzle is the 3D structure of the magnetic field threading dust clouds, which cannot be accessed through microwave observations alone, since they record integrated emission along the line of sight. Instead, observations of a large number of stars at known distances in optical polarization, tracing the same CMB-obscuring dust, can map the magnetic field between them. The Gaia mission is measuring distances to a billion stars, providing an opportunity to produce, the first-ever tomographic map of the Galactic magnetic field, using optical polarization of starlight. Such a map would not only boost CMB polarization foreground removal, but it would also have a profound impact in a wide range of astrophysical research, including interstellar medium physics, high-energy astrophysics, and galactic evolution. Taking advantage of our privately-funded, novel-technology, high-accuracy WALOP optopolarimeters currently under construction, we propose an ambitious optopolarimetric program of unprecedented scale that can meet this challenge: a survey of both northern and southern Galactic polar regions targeted by CMB experiments, covering >10,000 square degrees, which will measure linear optical polarization at 0.2% accuracy of over 360 stars per square degree (over 3.5M stars, a 1000-fold increase over the state of the art), combining wide-field-optimized instruments and an extraordinary commitment of observing time by Skinakas Observatory and the South African Astronomical Observatory.
Max ERC Funding
1 887 500 €
Duration
Start date: 2018-06-01, End date: 2023-05-31