1 00:00:00,012 --> 00:00:07,961 Let's now turn to two different extreme ends of early type galaxy properties. 2 00:00:07,961 --> 00:00:15,716 One is the super massive black holes and their nuclei and the other one is the 3 00:00:15,716 --> 00:00:21,667 dwarf family of galaxies. As it turns out super massive black holes 4 00:00:21,667 --> 00:00:28,136 Measured in millions and billions of solar masses, or even more, are ubiquitous. 5 00:00:28,136 --> 00:00:33,111 They are present in essentially every galaxy of substantial size near us. 6 00:00:33,111 --> 00:00:38,829 In most cases, they don't do very much; but sometimes they create/g material From 7 00:00:38,829 --> 00:00:43,402 outside and that causes burst of great luminosity and activity. 8 00:00:43,402 --> 00:00:49,237 Those are the active galactic nuclei, which we will discuss in more detail later 9 00:00:49,237 --> 00:00:53,018 in class. The super massive black hole paradigm for 10 00:00:53,018 --> 00:00:58,185 active galactic nuclei quasars and such is now very well established. 11 00:00:58,185 --> 00:01:03,884 And it's interesting to figure out Those super-massive black holes come from. 12 00:01:03,884 --> 00:01:09,182 If they're not doing anything very special, being recsys sources or a radio 13 00:01:09,182 --> 00:01:12,875 or something. One thing that we can do is probe their 14 00:01:12,875 --> 00:01:18,473 masses using stars as test particles. We can do this by measuring kinematics of 15 00:01:18,473 --> 00:01:22,091 stars in the very centers of early type galaxies. 16 00:01:22,091 --> 00:01:27,116 When this was done for the Milky Way, we found out that there is a 3 or 4 million 17 00:01:27,116 --> 00:01:32,584 solar mass black hole there, which is not very active, just sputters occasionally. 18 00:01:32,584 --> 00:01:36,209 But it could have been a luminous active nucleus in the past. 19 00:01:36,209 --> 00:01:41,723 And as it turns out, masses of these large black holes in cores of ellipticals or in 20 00:01:41,723 --> 00:01:46,664 fact all galaxies correlate remarkably well with a whole number of other 21 00:01:46,664 --> 00:01:51,929 properties of galaxies, and that is telling us something about formative and 22 00:01:51,929 --> 00:01:56,221 evolutionary mechanisms. We now, in fact, think about crawl 23 00:01:56,221 --> 00:02:00,220 evolution of galaxies and their super massive black holes. 24 00:02:00,220 --> 00:02:06,232 So here is one of the first cases, the small, elliptical satellite of Andromeda 25 00:02:06,232 --> 00:02:11,453 and it'll shown on the right is profile of its velocity dispersion. 26 00:02:11,453 --> 00:02:16,607 You can see there is a sharp spike in the middle, which is what you would expect if 27 00:02:16,607 --> 00:02:21,443 you were to embed a large point mass like a black hole in an otherwise normal 28 00:02:21,443 --> 00:02:24,948 galactic core. This will measure for many, many more 29 00:02:24,948 --> 00:02:28,660 galaxies, and several interesting trends were found. 30 00:02:28,660 --> 00:02:35,228 The first one was that the mass of the black hole is proportional to the total 31 00:02:35,228 --> 00:02:40,970 stellar mass of the host galaxy, amounting to something like 0.1%. 32 00:02:40,970 --> 00:02:47,419 That alone suggests that there is some sort of common formative mechanism. 33 00:02:47,420 --> 00:02:52,942 A more interesting correlation is between mass of the black hole and the velocity 34 00:02:52,942 --> 00:02:58,622 dispersion of its host galaxy measured at large radii, where the influence, dynamic 35 00:02:58,622 --> 00:03:02,246 of influence of black hole is completely negligible. 36 00:03:02,246 --> 00:03:07,532 So somehow properties of galaxies on scales of kilo-parsecs are related to the 37 00:03:07,532 --> 00:03:11,490 black holes in their cores which are micro microparsecs. 38 00:03:11,490 --> 00:03:17,116 The, there is something that couples them through 9 orders of magnitude in size. 39 00:03:17,116 --> 00:03:22,717 Another approach to this is by considering all of the quasar light ever emitted. 40 00:03:22,717 --> 00:03:27,620 We have now a reasonably good understanding of the evolution of active 41 00:03:27,620 --> 00:03:33,609 galaxy population as a function of time. And we can assume certain efficiency of 42 00:03:33,609 --> 00:03:39,483 accretions, say that maybe 10% of all matter that falls into black holes con, is 43 00:03:39,483 --> 00:03:45,713 converted into luminous output we can discuss that later, and then simply add up 44 00:03:45,713 --> 00:03:51,607 how much mass should have been accumulated through the history of universe. 45 00:03:51,607 --> 00:03:57,742 And if we do this, we find out that on average, you expect that typical luminous 46 00:03:57,742 --> 00:04:03,715 galaxy today would have about 10 million solar mass black hole in it's core. 47 00:04:03,715 --> 00:04:09,596 And Milky Way has a 3 or 4 million solar mass one so it's perfectly sensible. 48 00:04:09,596 --> 00:04:13,175 Andromeda one is maybe a little more massive. 49 00:04:13,176 --> 00:04:19,609 So this, can be compared directly to the measurements from kinematics in senses of 50 00:04:19,609 --> 00:04:25,535 super mass in black holes in galaxies. And we find out the two agree very well, 51 00:04:25,535 --> 00:04:31,745 and they correspond to the local average black hole density of about 500,000 solar 52 00:04:31,745 --> 00:04:37,865 masses per Cubic mega-parsec, which is about three orders of magnitude less than 53 00:04:37,865 --> 00:04:42,325 mass density of stars. An even more interesting relation was 54 00:04:42,325 --> 00:04:45,518 found by Laura Ferrarese and collaborators. 55 00:04:45,518 --> 00:04:50,880 And she estimated masses of dark halos of galaxies, from their kinematics. 56 00:04:50,881 --> 00:04:56,892 And it turns out that those are correlated with super massive black holes as well. 57 00:04:56,892 --> 00:05:00,709 Superbly well. But interestingly, in a non-linear 58 00:05:00,709 --> 00:05:07,117 fashion, whereas the masses of black holes were proportional to the luminous stellar 59 00:05:07,117 --> 00:05:13,294 mass or at least for the bulge component. Here we find out that they're proportional 60 00:05:13,294 --> 00:05:18,396 to a steeper power of halo mass. Meaning that more massive halos, more 61 00:05:18,396 --> 00:05:23,427 massive galaxies, therefore, are more efficient in making black holes. 62 00:05:23,427 --> 00:05:28,393 You could understand that by the more massive ones being more efficient in 63 00:05:28,393 --> 00:05:32,857 obstracting merging fuel. And, maybe that's what's going on. 64 00:05:32,857 --> 00:05:38,071 But what's remarkable about these relations is that they have such a small 65 00:05:38,071 --> 00:05:41,573 scatter. We think that merging is a fairly random 66 00:05:41,573 --> 00:05:47,438 [inaudible] process efficiency will vary and yet somehow, after Hubble time or so 67 00:05:47,438 --> 00:05:53,667 There is remarkably sharp correlations. So we can qualitatively understand where 68 00:05:53,667 --> 00:05:59,517 they come from but their quantitative understanding, why they're so sharp is 69 00:05:59,517 --> 00:06:03,707 still a mystery. And here they are, all on same plot. 70 00:06:03,707 --> 00:06:09,366 Top left is proportion between black hole mass, and the luminous stellar mass. 71 00:06:09,366 --> 00:06:14,265 Then there is proportion between black hole mass and velocity dispersion. 72 00:06:14,265 --> 00:06:18,799 Which looks a little bit like Tally-Fisher or Faber-Jackson relation. 73 00:06:18,799 --> 00:06:22,359 Again, circular velocity, and against the halo mass. 74 00:06:22,359 --> 00:06:25,437 Proportional to the halo mass to roughly 1.6. 75 00:06:25,437 --> 00:06:29,366 And now for something entirely different, dwarf galaxies. 76 00:06:29,366 --> 00:06:34,608 In Hubble's days, and for some time after people thought there is one kind of thing 77 00:06:34,608 --> 00:06:38,728 called dwarf ellipticals and they're just small ellipticals. 78 00:06:38,728 --> 00:06:43,834 Now we know this is not the case. They're a very different family of objects 79 00:06:43,834 --> 00:06:47,680 and in fact they may be two different families of objects. 80 00:06:47,680 --> 00:06:54,377 In addition to simple division of being gas poor or gas rich, in making stars. 81 00:06:54,377 --> 00:06:59,162 The reason why we think they're very different is that they follow very 82 00:06:59,162 --> 00:07:04,832 different correlations between their Fundamental properties which I'll show you 83 00:07:04,832 --> 00:07:07,888 in a moment. And those correlations a product of 84 00:07:07,888 --> 00:07:12,784 formative evolutionary processes for galaxies then that suggests that they're 85 00:07:12,784 --> 00:07:16,411 two different paths and therefore two different families. 86 00:07:16,411 --> 00:07:21,454 As it turns out, dwarf galaxies, dwarf spheroidals in particular are totally dark 87 00:07:21,454 --> 00:07:25,587 matter dominated. They have higher mass to light ratios then 88 00:07:25,587 --> 00:07:29,718 Any other galaxies, and we think we understand why this is. 89 00:07:29,718 --> 00:07:35,640 Again, remembering the scenario where supernova explosions can expell gas from 90 00:07:35,640 --> 00:07:39,943 galaxies. They can do so in shallow potential wells 91 00:07:39,943 --> 00:07:44,905 thus removing variance. But super nova shocks would not effect 92 00:07:44,905 --> 00:07:48,512 dark matter at all. So dark matter will stay. 93 00:07:48,512 --> 00:07:53,978 So, lower luminosity galaxies will be more efficient in losing their luminous mass 94 00:07:53,978 --> 00:07:58,877 while retaining the dark matter. And therefore you expect them to be more 95 00:07:58,877 --> 00:08:02,782 dark matter dominated. Which is exactly what's observed. 96 00:08:02,782 --> 00:08:08,292 So here is a set of correlations produced by John Kormendy that shows some 97 00:08:08,292 --> 00:08:14,570 properties of elliptical galaxies, dwarf spheroidals, and globular clusters, which 98 00:08:14,570 --> 00:08:20,418 really don't belong in this diagram at all, but they're there just for symmetry's 99 00:08:20,418 --> 00:08:25,943 sake as all stellar systems. And they show central surface brightness 100 00:08:25,943 --> 00:08:31,088 versus radius in the top left. The central surface brightness versus 101 00:08:31,088 --> 00:08:35,601 luminosity, top right. The velocity dispersion versus radius in 102 00:08:35,601 --> 00:08:40,957 the lower left and velocity dispersion versus luminosity on the lower right. 103 00:08:40,957 --> 00:08:46,867 The two families with thicker symbols are elliptical galaxies and dwarf ellipticals 104 00:08:46,867 --> 00:08:51,289 and dwarf spheroidals. The little dots are globular clusters. 105 00:08:51,289 --> 00:08:56,657 And you can see that obviously they separate very cleanly in this parameter 106 00:08:56,657 --> 00:08:59,807 space. So let's look at this in a little more 107 00:08:59,807 --> 00:09:02,727 detail. This is just plot of mean surface 108 00:09:02,727 --> 00:09:07,011 brightness, with an effective radius, versus luminosity. 109 00:09:07,011 --> 00:09:12,606 And, whereas for normal ellipticals, which is the upper right set with the red line 110 00:09:12,606 --> 00:09:18,033 going though them There is a trend that the more luminous ones have lower surface 111 00:09:18,033 --> 00:09:23,244 brightness because they have more diffuse surface brightness profiles. 112 00:09:23,244 --> 00:09:26,950 The exact opposite trend happens for the dwarf galaxies. 113 00:09:26,950 --> 00:09:31,573 Not only is the trend opposite, but the intercept is different as well. 114 00:09:31,573 --> 00:09:38,989 So in the region where they overlap the difference or rather the ratio between 115 00:09:38,989 --> 00:09:46,741 surface brightness at the given luminosity implies the ratio of 3 dimensional 116 00:09:46,741 --> 00:09:54,037 luminosity densities by about the fact of 1,000 or more which is like between 117 00:09:54,037 --> 00:09:59,074 uranium and air. So these are not dwarf elliptical they're, 118 00:09:59,074 --> 00:10:05,466 a different kind of thing, they're is just like calling cotton puffs, dwarf canon 119 00:10:05,466 --> 00:10:12,096 balls and here is really telling diagram of mass to light ratio versus luminosity. 120 00:10:12,096 --> 00:10:17,971 I did not plot globular clusters and elliptical, non ellipticals as individual 121 00:10:17,971 --> 00:10:22,002 points, just indicated where are they in this diagram. 122 00:10:22,002 --> 00:10:25,731 And I plotted dwarf spheroidals as solid dots and. 123 00:10:25,731 --> 00:10:30,217 Dwarf ellipticals like those around Andromeda has the open symbols. 124 00:10:30,217 --> 00:10:35,527 And you can see that there is this branch of dwarf spheroidals that just shoots up, 125 00:10:35,527 --> 00:10:40,042 reaching mass to light ratios of the order of 100 at very low mass end. 126 00:10:40,042 --> 00:10:45,130 This has been confirmed by many, many subsequent observations now we know more 127 00:10:45,130 --> 00:10:50,066 of these galaxies. This will lead into the next discussion, 128 00:10:50,066 --> 00:10:57,486 about how we can use scaling relations in correlations for galaxy families to learn 129 00:10:57,486 --> 00:11:02,475 something about their internal physics information.