Young Stars in the Galactic Center Jessica R. Lu Institute for Astronomy University of Hawaii, Manoa Tuan Do, Andrea Ghez, Mark Morris, Sylvana Yelda, Keith Matthews, Will Clarkson, Andrea Stolte, Nate McCrady, Jay Anderson
HST NICMOS Spitzer IRAC
Why do we study young stars at the GC? The Answer: More Questions... How, where, when did the young stars form? Does the environment effect the star formation process and its outcome? What is the ultimate fate of the clusters? What is the interplay between star formation and black hole accretion?
Young Nuclear Cluster
0.4 pc
0.4 pc Overlays from Do 2009, 2013, in prep; Bartko 2013
0.4 pc Overlays from Do 2009, 2013, in prep; Bartko 2013
Astrometry proper motion errors at 1 km/s Yelda et al. submitted (see poster)
Origin theories include in situ formation or infalling clusters. Stars formed in situ (where we see them today) in a disk around the black hole?? Stars formed far from the black hole in a large cluster which then spiraled via dynamical friction?
The steep radial profile of the disk suggests in situ formation. Observations Theory In-falling cluster In Situ Lu+ 2009 also Bartko+ 2009, Do+ 2009, 2013 Berukoff & Hansen 2006
Eccentricity of disk not circular. Yelda+ submitted see poster
3D dynamics show 20% disk + 80% Cloud dump Cloud-cloud collision Figure from Hobbs & Nayakshin 2009
In situ formation is favored.
In situ formation is favored. Environment: high temperature gas densities of >10 10 cm -3 to overcome tidal shear high B fields high stellar density
In situ formation is favored. Environment: high temperature gas densities of >10 10 cm -3 to overcome tidal shear high B fields high stellar density Does the IMF vary in this extreme environment?
The observed luminosity function is not matched by a Salpeter IMF. Lu+. 2013 Do+ 2013
We find the properties of the observed cluster using synthetic models and Bayesian inference.
We find the properties of the observed cluster using synthetic models and Bayesian inference. Initial Mass {m i } Function (Mcl, multiples)
We find the properties of the observed cluster using synthetic models and Bayesian inference. Initial Mass {m i } Stellar Function (Mcl, multiples) Evolution Model (t, Z) {L i, T eff,i, g i }, N WR
We find the properties of the observed cluster using synthetic models and Bayesian inference. Initial Mass {m i } Stellar Function (Mcl, multiples) Evolution Model (t, Z) {L i, T eff,i, g i }, N WR {K i }, N WR Stellar Atmosphere Model (d, AK)
We find the properties of the observed cluster using synthetic models and Bayesian inference. Initial Mass {m i } Stellar Function (Mcl, multiples) Evolution Model (t, Z) {L i, T eff,i, g i }, N WR Compare with observations {K i }, N WR Stellar Atmosphere Model (d, AK)
Detecting binaries! Must include in models. Lu+. 2013 see also Pfuhl+ for RV binaries
We observe a moderately top-heavy IMF, above 8 Msun. IMF slope = 1.7 +/- 0.2 Salpeter = 2.35 is ruled out with 4σ confidence Lu+. 2013 see also Bartko+ 2010
YNC Future Studies astrometry ages well more spectra multiplicity pre-mainsequence Lu+. 2013
Arches Cluster: 10 4 Msun, 2.5 Myr
Proper motions successfully separate field stars from Arches cluster members. Stolte+ 2008, Clarkson+ 2012
Revealed infrared excess sources in the Arches: protoplanetary disks. Stolte+ 2010 Disk Fraction = 6% Low value suggests disk depletion compared with lower mass clusters.
Arches internal velocity dispersion of ~5 km/s, gives total enclosed mass of 10 4 Msun. Clarkson+ 2012
Arches internal velocity dispersion of ~5 km/s, gives total enclosed mass of 10 4 Msun. Clarkson+ 2012
The dynamical mass estimate is inconsistent with a normal IMF. Clarkson+ 2012 Photometric IMFs down to 10 Msun Espinoza+ 2009, Habibi+ 2013
The dynamical mass estimate is inconsistent with a normal IMF. Normal IMF Clarkson+ 2012 Photometric IMFs down to 10 Msun Espinoza+ 2009, Habibi+ 2013
The dynamical mass estimate is inconsistent with a normal IMF. Normal IMF Viable Options: Bottom-light IMF Top-heavy IMF Clarkson+ 2012 Photometric IMFs down to 10 Msun Espinoza+ 2009, Habibi+ 2013
The dynamical mass estimate is inconsistent with a normal IMF. Normal IMF Viable Options: Bottom-light IMF Top-heavy IMF Top Heavy Clarkson+ 2012 Photometric IMFs down to 10 Msun Espinoza+ 2009, Habibi+ 2013
The dynamical mass estimate is inconsistent with a normal IMF. Normal IMF Viable Options: Bottom-light IMF Top-heavy IMF Top Heavy Bottom Light Clarkson+ 2012 Photometric IMFs down to 10 Msun Espinoza+ 2009, Habibi+ 2013
Arches and Quintuplet Orbits Stolte+ 2008 Stolte+ in prep
Stolte+ 2008, and in prep In Front Behind Quintuplet Arches outer X2
Arches/Quintuplet: Future Work
2-3 Myr 4-6 Myr 3-5 Myr
Why do we study young stars at the GC? The Answer: More Questions... How, where, when did the young stars form? Does the environment effect the star formation process and its outcome? What is the ultimate fate of the clusters? What is the interplay between star formation and black hole accretion?
One more thing...
Milky Way Young Nuclear Star Cluster Andromeda Young Nuclear Star Cluster - 6 Myr cluster - gas rich - 150 Myr cluster - no gas
Milky Way Young Nuclear Star Cluster Andromeda Young Nuclear Star Cluster - 6 Myr cluster - gas rich - 150 Myr cluster - no gas
NASA, ESA, R. Bender (MPE),! T. Lauer (NOAO), J. Kormendy (UT)! Lauer+ 2012
From what did the young stars form? NASA, ESA, R. Bender (MPE),! T. Lauer (NOAO), J. Kormendy (UT)! Lauer+ 2012
Jessica R. Lu Institute for Astronomy, University of Hawaii at Manoa Ethan Tweedie Photography