Annual Report 2011 Max Planck Institute for Astronomy

More documents

Recommendations

Info

62 III. Selected Research Areas q 0.9 0.86 0.82 0.9 0.86 0.82 a) c) –0.3 –0.2 –0.1 0 Fig. III.3.5: Posterior distribution for median projected axis ratio (shape) versus velocity anisotropy at the end of an MCMC run for Centauri with the points coloured according to their likelihood (red high, blue low). a): likelihood for x proper motions only, b) likelihood for y proper motions only, c) likelihood for line-of-sight velocities only, d) total likelihood. The foreground or background population) are removed via a series of cuts before proceeding with the modeling; this is a tricky process – make the cuts too conservative and true members will be excised as well as the contaminants, make the cuts too generous and contaminants will still remain. A better approach is to include all stars in a model, both likely members and suspected contaminants, and allow for the presence of a contaminant population in the likelihood calculations. As our models have many parameters a simple grid search is not feasible, so we turn to Markov-Chain Monte Carlo (MCMC) methods in order to sample the large parameter space efficiently. One prime example that highlights what we are currently able to achieve is the Galactic globular cluster w Centauri. Located only 5 kpc from the Sun, it is large and bright and has been observed many times with many different instruments, over a long time baseline. As a result, there are line-of-sight velocities and metal abundances available for thousands of stars, and proper motions measurements available for hundreds of thousands 0.1 ln L x ln L z b) d) ln L y ln L total 0.2 –0.3 b –0.2 –0.1 0 0.1 0.2 degeneracy between shape and anisotropy is seen in the scatter of the points. It is clear from the first three panels that the individual velocities do not converge on the correct answer; however their combination (as shown in panel d) does break the degeneracy and converges nicely. of stars. w Centauri is an interesting object to study as it demonstrates many qualities in common with globular clusters, such as an apparent absence of dark matter, and also many qualities in common with dwarf spheroidal galaxies, such as a complex star formation history. There is also an ongoing debate concerning the presence (or absence) of an intermediate-mass black hole (IMBH) at its center. High-quality data and sophisticated modeling techniques should enable us to finally answer some of the questions that linger over the nature of this curious object and how it has formed and evolved. The result of one MCMC model run for w Centauri is shown in Fig. III.3.5 for two of our parameters: the median deprojected axis ratio (q, a proxy for shape) and velocity anisotropy (b). These plots demonstrate the shape-anisotropy degeneracy that exists, and that proper motions and line-of-sight velocities must be used together in order to break the degeneracy. A second object to which we are applying our modeling tools is the prototypical core collapsed Galactic globular cluster M 15. A longstanding debate is wheth- Credit: Glenn van de Ven
er the increase in the mass-to-light ratio (M/L) toward the center is purely due to stellar remnants that arrived at the center as a result of mass segregation, or if there is also an IMBH present. Since with our discrete likelihood fitting method we do not lose spatial information as in the case of binning, we can measure the dark central mass to higher accuracy than before. Our resulting density profile for M 15 is in excellent agreement with predictions from stellar cluster simulations, without the presence of an IMBH. This is a promising start. However, in these preliminary models we have not yet chemical information and we have used simplified contamination models. III.3 Dynamics of Galaxies: inferring their mass distribution and formation history 63 Nevertheless, these results demonstrate that we have the machinery in place to handle both current and upcoming datasets in the Local Group, now we can work on further developing the maximum likelihood techniques and incorporating more information to truly exploit the data. Glenn van de Ven, Laura Watkins, Remco van den Bosch, Mariya Lyubenova, Akin Yildirim, Alex Büdenbender, Ronald Läsker, Vesselina Kalinova, Chao Liu, Mark den Brok
Page 1 and 2:
Max Planck Institute for Astronomy
Page 3 and 4:
Max Planck Institute for Astronomy
Page 5:
Contents Preface ..................
Page 8 and 9:
6 I. General Credit: MPIA / AMQ I.
Page 10 and 11:
8 I. General lows us to understand
Page 12 and 13:
10 I. General Credit: CAHA I.2 Obse
Page 14 and 15: 12 I. General in December 2009, the
Page 16 and 17: 14 I. General Credit: eSo/l. calça
Page 18 and 19: 16 I. General Point source sensitiv
Page 20 and 21: 18 I. General I.3 National and Inte
Page 22 and 23: 20 I. General Credit for both figur
Page 24 and 25: 22 I. General I.4 Educational and P
Page 26 and 27: 24 II. Highlights II. Highlights II
Page 28 and 29: 26 II. Highlights N 10 8 6 4 2 0 gm
Page 30 and 31: 28 II. Highlights rotate with respe
Page 32 and 33: 30 II. Highlights II.3 In what Gala
Page 34 and 35: 32 II. Highlights These are galaxie
Page 36 and 37: 34 II. Highlights II.4 Starbursting
Page 38 and 39: 36 II. Highlights Credit: A. van de
Page 40 and 41: 38 II. Highlights and may solve a l
Page 42 and 43: 40 III. Selected Research Areas Mas
Page 44 and 45: 42 III. Selected Research Areas low
Page 46 and 47: 44 III. Selected Research Areas Num
Page 48 and 49: 46 III. Selected Research Areas R [
Page 50 and 51: 48 III. Selected Research Areas III
Page 52 and 53: 50 III. Selected Research Areas N /
Page 54 and 55: 52 III. Selected Research Areas 6 p
Page 56 and 57: 54 III. Selected Research Areas Fig
Page 60 and 61: 58 III. Selected Research Areas the
Page 62 and 63: 60 III. Selected Research Areas the
Page 68 and 69: 66 III. Selected Research Areas Tra
Page 70 and 71: 68 III. Selected Research Areas M51
Page 72 and 73: 70 III. Selected Research Areas Cre
Page 74 and 75: 72 IV. Instrumental Developments an
Page 86 and 87: 84 V. People and Events times a yea
Page 88 and 89: 86 V. People and Events Credit: D.
Page 90 and 91: 88 V. People and Events Fig. V.2.2c
Page 92 and 93: 90 V. People and Events Fig. V.2.4a
Page 94 and 95: 92 V. People and Events Credit: C.
Page 96 and 97: 94 V.3 Honors and Awards Ernst Patz
Page 98 and 99: 96 V. People and Events Andreas Sch
Page 100 and 101: 98 Staff Schultz (since 8.9.), Scor
Page 102 and 103: 100 Staff / Departments 14.-18. Nov
Page 104 and 105: 102 Teaching Activities / Service i
Page 106 and 107: 104 Further Activities / Compatibil
Page 108 and 109: 106 Cooperation with Industrial Fir
Page 110 and 111: 108 Conferences, Scientific, and Po
Page 112 and 113: 110 Conferences, Scientific, and Po
Page 114 and 115:
112 Conferences, Scientific, and Po
Page 116 and 117:
Page 118 and 119:
Page 120 and 121:
118 Haus der Astronomie interns sup
Page 122 and 123:
120 Publications Publications In Jo
Page 124 and 125:
122 Publications Beuther, H., H. Li
Page 126 and 127:
124 Publications formation efficien
Page 128 and 129:
126 Publications Erroz Ferrer: Gran
Page 130 and 131:
128 Publications Hansen, S. H., A.
Page 132 and 133:
130 Publications L. Michaud, G. Mon
Page 134 and 135:
132 Publications Notices of the Roy
Page 136 and 137:
134 Publications Riechers, D. A., F
Page 138 and 139:
136 Publications Hayano, T. Henning
Page 140 and 141:
138 Publications B. Lawton, J. M. L
Page 142 and 143:
140 Publications Dzyurkevich, N., N
Page 144 and 145:
142 Publications Mordasini, C., Y.
Page 146 and 147:
144 Publications Astrophysics of Pl
Page 149 and 150:
A656 B 37 K 9702 Eppelheim L 543 Pa
show all

Annual Report 2011 Max Planck Institute for Astronomy

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?