Hunting Black Holesprogetti.dfa.unipd.it/GALFOR/DIDATTICA/STELLAR... · 2020. 4. 24. · The...
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Antonino P. Milone Hunting Black Holes A. P. Milone Stellar Populations University of Padova, 2020 Antonino P. Milone
Transcript of Hunting Black Holesprogetti.dfa.unipd.it/GALFOR/DIDATTICA/STELLAR... · 2020. 4. 24. · The...
Antonino P. Milone
Hunting Black Holes
A. P. Milone Stellar Populations University of Padova, 2020
Antonino P. Milone
Back to past lectures:Simple stellar population
A. P. Milone Stellar Populations University of Padova, 2020
– A simple stellar population (SSP) is an assembly of coeval, initially chemically homogeneous single stars.
– A SSP is described by four main parameters: i) age, ii) chemical composition (Y, Z),
iii) initial mass function.
Figure. Simple stellar population.
The initial mass function (IMF)
A. P. Milone Stellar Populations University of Padova, 2020
– The IMF is an empirical function that describes the distribution of mass in a stellar population.
Salpeter (1955) proposed a single power-low IMF:
where M is the stellar mass,n is the number density of stars, k is a constant
Hence dn/dM is the density of stars with masses between M and M+dM
The initial mass function
A. P. Milone Stellar Populations University of Padova, 2020
– Kroupa (2001) suggested a ‘segmented’ IMF
1/2 solar to high mass stars
Low-mass stars
Brown Dwarfs
Kroupa (2001)
The initial mass function
A. P. Milone Stellar Populations University of Padova, 2020
The initial mass function
A. P. Milone Stellar Populations University of Padova, 2020
Present-day mass function (PDMF) vs. IMF
The initial mass function
A. P. Milone Stellar Populations University of Padova, 2020
Present-day mass function (PDMF) vs. IMF
Pleyades PDMFMoraux et al. (2004)
The initial mass function
A. P. Milone Stellar Populations University of Padova, 2020
Present-day mass function (PDMF) vs. IMF
De Marchi et al. (2010) (Bastian et al. 2010 version)
The initial mass function
A. P. Milone Stellar Populations University of Padova, 2020
Present-day mass function (PDMF) vs. IMF
Challenges:– Clusters’ IMF is changedby dynamics.
– Multiple stars: the IMF issensitive to the binary fractionand the mass-ratio distribution of binaries.
– we need to be careful to the statistics of the IMF!
– Is IMF Universal?Does it depend on the environment?Is it constant in time? De Marchi et al. (2010)
(Bastian et al. 2010 version)
The brightness of the turn off depends from age.
The turn off is considered as a chronometer provided by stellar evolution
Observational planeObservational plane
Back to past lectures: Isochrones and ageBack to past lectures: Isochrones and age
Isochrones and metallicityIsochrones and metallicity
Isochrones and metallicityIsochrones and metallicity
Isochrones and heliumIsochrones and helium
Helium-rich MS and RGB stars are bluer than helium-poor stars with the same luminosity
Age=13 Gyr
[Fe/H]=-1.00
Observational planeObservational plane
Isochrones and heliumIsochrones and helium
Wide color baselines are more-sensitive to helium variations than narrow color baselines
Observational planeObservational plane
Isochrones and alpha elementsIsochrones and alpha elements
Isochrones and alpha elementsIsochrones and alpha elements
Isochrones and alpha elementsIsochrones and alpha elements
A. P. Milone Stellar Populations University of Padova, 2020
Hunting Black Holes
A. P. Milone Stellar Populations University of Padova, 2020
Hunting Black Holes
M87, Harms et al. (1994)
Radial velocity of ionized gas show strong evidence of Keplerian rotation around a supermassive black hole.
A. P. Milone Stellar Populations University of Padova, 2020
Hunting Black Holes
A. P. Milone Stellar Populations University of Padova, 2020
M-sigma relation is a relation between the velocity dispersion a galactic bulge and the mass
of the supermassive black hole.
Hunting Black Holes
A. P. Milone Stellar Populations University of Padova, 2020
Sagittarius A is a compact radio source at the center of the Millky Way.
The central light year of the Galaxy contains a dense star cluster.
Hunting Black Holes
A. P. Milone Stellar Populations University of Padova, 2020
Sagittarius A appears to be slinging many of the cluster’s constituent members at incredible speeds...
Hunting Black Holes
Genzel et al. (2010)
A. P. Milone Stellar Populations University of Padova, 2020
…So fast that the presence of a Black Hole is now a ‘paradigma’
Hunting Black Holes
Genzel et al. (2010)
A. P. Milone Stellar Populations University of Padova, 2020
Black-hole mass: 4.10±0.60×10^6 Msun
Hunting Black Holes
Gillessen et al. (2009)
Luminosity profiles of star clusters
Zocchi et al. (2012)
A. P. Milone Stellar Populations University of Padova, 2020
A. P. Milone Stellar Populations University of Padova, 2020
Hunting intermediate-mass Black Holes
Surface-brightness profile of Omega Centauri seems not consistent with the Trager’s fit.
Noyola et al. (2008)
A. P. Milone Stellar Populations University of Padova, 2020
Hunting intermediate-mass Black Holes
Observations are consistent with:
Profile for the luminous component (continuous line) plus a dark component (dashed line).
Noyola et al. (2007, 2011)
A. P. Milone Stellar Populations University of Padova, 2020
Hunting intermediate-mass Black HolesLine-of-sight velocity dispersions in two 5×5” fields
Observations are consistent with a black hole of ~40,000 solar masses
Noyola et al. (2008)
A. P. Milone Stellar Populations University of Padova, 2020
Hunting intermediate-mass Black Holes
M-sigma relation for intermediate-mass black holes in globular clusters ?
Source: Nora Lutzgendorf
A. P. Milone Stellar Populations University of Padova, 2020
Hunting intermediate-mass Black Holes
High-precision proper motions for ~53,000 stars in the central ~2 arcmin region from multi-epoch HST data challenge the presence of IMBH in Omega Cen
Anderson & van der Marel (2010)
A. P. Milone Stellar Populations University of Padova, 2020
Hunting intermediate-mass Black Holes
No evidence for the cusp
van der Marel & Anderson (2010)
The mass of the possible black hole, if present must be smaller than ~12,000 Msun
