Unveiling the Mass of Galaxies with Vera Rubin
This week I am attending a conference at Queen’s University in Kingston (Ontario, Canada) with I think the longest name I have ever seen. It’s called “A Celebration of Vera Rubin’s Life. Unveiling the Mass: Extracting an Interpreting Galaxy Masses.” I was very excited to attend this conference. Vera Rubin has always been a role model of mine (hard to avoid as a women studying galaxies) and as well as her the list of speakers includes many people who’s work I know and respect. It also has the advantage of being held in Kingston where a close friend (and fellow astronomer) from graduate school is now living with her very new baby.
This morning the introductory talks did not disappoint. We heard anecdotes from Vera Rubin about her work as a young scientist just trying to interpret the observations she was making on the rotation curves of galaxies (observations that provided the first strong evidence for dark matter in galaxies). She talked about a 1962 paper she did with students measuring the rotation curve of the Milky Way, and her regrets on not noticing that dark matter must have been present when she measured a similar “flat” rotation curve for the Andromeda galaxy 13 years later. She further impressed me by dating another anecdote (about discovering a galaxy in which the stars rotated in two directions) by the year her youngest child learned to walk (1961). Not only is Vera Rubin an incredibly successful and famous astronomer, but she managed to have 4 children (at least one of whom followed her into astronomy) during the period she did most of her famous work. Wow! I got to talk with her a little bit this morning at coffee, and she’s also a very nice person.
As well as enjoying the many talks by leaders in the field of galaxy evolution, I am presenting a poster on my work on dust reddening of Galaxy Zoo spirals which you have heard about several times before (eg. Blue Sky and Red Spirals, and from when I presented it at the 2009 European Week of Astronomy). This work has relevance to the masses of galaxies as dust is a significant source of error on estimates of the total mass of stars in a galaxy – at the simplest level dust hides the stars.
I was encouraged to share my poster on this blog, so if you wish to have a closer look at it you can download it (pdf). Of course this poster is aimed at explaining my work to other astronomers not to a general audience. If you have questions about it I encourage you to first look at my more general explanation of the work Blue Sky and Red Spirals and I am also happy to answer questions in the comments below.
One little details which is not explained in the poster is that the images of galaxies on both the right and left are not random. On the right I show edge-on spiral galaxies ordered from bluest (at the bottom) to reddest (at the top). On the left I show all face-on galaxies, also ordered in the same way. My definition of blue versus red comes from a measured difference in the brightness seen through 2 filters (in this case the SDSS g and z filters), so is not always obvious to the eye – also remember that it is the average colour of the whole galaxy, and some have significantly different colours in their centres to in the outskirts. However one of the interesting results coming from this work is that even though on average dust reddens galaxies as they become more inclined (as they go from face-on to edge-on) some face-on galaxies are much redder than some edge-on galaxies. This shows that while dust is important to the colour of a spiral galaxy it is clearly not the most important factor. This is very good news for those of us interested in red spirals as an evolutionary stage!
If anyone is in the Kingston area there will be a public lecture at 8pm tomorrow night given by Prof. Sandy Faber. It’s on the Queen’s Campus in the Biosciences Building, Room 1101. I include the poster below. Sandy Faber was a student of Vera Rubin’s and gave a very nice review talk this morning about her early work on dark matter during this time. I encourage you to attend if you are able – I think it will be a very nice public astronomy talk.
Dust pathfinding with Galaxy Zoo
Now that spring classes are over, I’m catching up with lots of things. These include making color-composite images from our latest observations at the WIYN 3.5-meter telescope in Arizona done to follow up overlapping-galaxy pairs from the Forum. Here are three samples, showing how much more detail we can see with long exposures one the objects have been found from the SDSS data. In SDSS J215311.30-073533.5, the WIYN images show just the kind of thing we’re looking for – dust in spiral arms silhouetted against the light of the background galaxy. First here is the SDSS image, then the WIYN picture below it.
SDSS 2153-07 WIYN image
Read More…
Pictures from AAS
The AAS meeting just ended, and in a few minutes I’ll be giving Lucy from the Zoo Education Team a ride to Caltech, which is just down the street. Georgia sent me some photos from the three Galaxy Zoo education posters that we presented here.
Here is my poster, describing the irregular galaxies project:
Here is Pamela’s poster describing the results of our survey into the reasons you participate in Galaxy Zoo:
And, last but not least, here is Georgia’s poster describing our plans for future user testing of the Zoo 2 website:
It was a very successful meeting, and a lot of people came by the poster to ask questions or share their own results.
I’m headed back home at 11 PM tonight. It’s been a great trip, but I’m looking forward to going home!
Watch the AAS Citizen Science session now!
The International Year of Astronomy citizen science session at AAS is going on *right now*! Pamela’s team is live-streaming the session. You can see it at http://tinyurl.com/mmm5n4 .
Live from the AAS International Year of Astronomy Press Conference, part 2
11:08 AM: Pamela: “Galaxy Zoo takes long collaborator lists to a whole new level.” She’s showing a small sample of all the names from the Zoo 1 poster. Next, she’s talking about Zoo 2, and telling the story of 100 hours of astronomy challenge – 1 million galaxies in 100 hours. We thought this was an ambitious goal, but you did 2.6 million!
11:09 AM: “We now have a group of volunteers larger than the Italian Army.” Chris leaned over to me and says, “We need to update that, so we can figure out who we can invade now.” 🙂
11:11 AM: Now she’s revealing the research result – it’s the “Old Galaxies Spin in Sync” discovery that Raul Jimenez posted about yesterday. Read Raul’s post for more about that. I couldn’t reveal the result before now because there was a press embargo. Pamela is now emphasizing that star formation history is the *only* thing that matches up with galaxy spin direction.
11:13 AM: In addition to Raul’s spin result, Pamela is talking about the discoveries that are coming out of Daniel’s mergers research. She’s showing a picture of mergers divided up by your confidence of how likely it was that it was truly a merger. The biggest discovery from your merger classifications is that about 1-3% of galaxies are undergoing major mergers. Pamela: “this work would not have been possible without the participation of large numbers of Zooites.” Great job, everyone – you made this press conference possible!
11:16 AM: Now it’s question time from reporters – I’ll try to record the Zoo-related questions and answers.
11:19 AM: Question: “What’s the correlation between different Zoo members in terms of classification?” Answer: We were able to build separate samples based on agreement between Zooites, called “clean,” “cleanest,” and “superclean,” based on agreement between 60%, 80%, and 95% of Zooites.
11:24 AM: Question: “How do you account for human bias when classifying clockwise and counterclockwise spirals?” Answer: When we first noticed an extra amount of counterclockwise galaxies, we mirrored images of the galaxies. When you classified the mirrored images, you found the same excess of counterclockwise galaxies, showing that it’s a human bias rather than something strange about the universe. Now that we know about the bias, we correct for it.
That’s the end of the press conference. Later today, I’ll go back and add some links to these posts for more information. Do any of you have any questions about anything that was said here?
Live from the AAS International Year of Astronomy Press Conference, part 1
The press conference is about to start. The topic of the press conference is the U.S. International Year of Astronomy program. Pamela is the lead for the New Media team, so she is representing the team as one of the four participants. The participants are:
-Doug Isbell, US IYA 2009 chair
-Steve Pompea, NOAO
-Connie Walker, NOAO
-Pamela, SIUE
The four panelists are sitting at an elevated table at the front of the room. I should mention that the International Year of Astronomy is a big deal here in Pasadena, home of Caltech – there are signs on Paseo Colorado, the main shopping area.
10:34 AM: The AAS’s Deputy Press Officer is introducing the Panel. Doug is described as the “SPOC” (pronounced Spock), the single point of contact for the U.S. program. Rick thanked Pamela for livecasting the press conference, and I do too. Thanks, Pamela!
10:36 AM: And so it begins, with Doug giving an overall introduction to the project. IYA has been endorsed by the United Nations, and 141 countries have active programs. One of the goals is to get millions of people to look through telescopes. Doug is also pointing out the International Secretary, Pedro Russo from ESO.
10:38 AM: Doug is talking about the IYA program. His slide has a screenshot of the U.S. House of Representatives endorsing a resolution in support of IYA. He also mentions 100 Hours of Astronomy, which many of you remember from the Zoonometer.
10:44 AM: Doug had an endearing typo on his slide – he listed the website as astronomy20009.org. Rick said, “Doug, we will not stick with this for 20,000 more years,” to great laughter, including Doug.
10:45 AM: Steve is now talking about the Galileoscope, a small telescope that has been built and is about to be sold. The design criterion for the telescope was that it must be able to see the rings of Saturn – from the beginning, they made all decisions with the rings of Saturn in mind. The Galileoscopes are now shipping, and are about to be sold for $15. These are small but high-quality telescopes, and $15 is an amazing price. Steve quotes Sky and Telescope in saying that they usually don’t recommend telescopes for under $200, but they were recommending this telescope for $15. It is a very cool project.
10:48 AM: There are 3 ways to use the Galileoscope – a 25x eyepiece, a 50x eyepiece, and a Galilean 17x eyepiece. The different lenses allow it to serve as an optics lab as well as a telescope. There are student activities called “In the Footsteps of Galileo” in which students make some of the same observations Galileo did, and also some activities on different types of lenses. He’s now showing a picture of the Moon that was taken through a Galileoscope, which is quite a good picture. And I should have mentioned earlier that Steve has a Galileoscope kit in front of him – I’ll try to post a picture of both the kit and the built telescope later.
10:55 AM: Next is Connie Walker from NOAO talking about Dark Skies programs, including the “Globe at Night” project, where volunteers make observations of the sky light levels and report them online. She says that about 2/3 of people in the U.S. cannot see the Milky Way.
10:57 AM: With all this in mind, Dark Skies was chosen as a cornerstone program of the U.S. IYA. The main project of the Dark Skies program is Globe @ Night (link coming soon). The program has been going on for a few years, but this has been their biggest year, with more than 15,000 observations taken. The average star magnitude reported is about 3 or 4 (more explanation of this coming soon).
11:02 AM: Connie is now giving an example of 3,400 measurements taken near the town of Granger, Indiana. They made a lego model of a map of their observations, where different colors of legos represented the faintest stars they could see from that spot. This is a very cool example of scientific visualization; I’ll try to find more details about it soon. Next, she’s showing examples from Norman, Oklahoma, where the program had the support of the mayor. There is a bright spot in the map – an area where it’s very hard to see the sky – that Connie says is the University of Oklahoma football stadium.
11:06 AM: For more information about dark skies, see http://www.darkskiesawareness.org
11:07 AM: Yay, Pamela is going next! Moving to a different thread.
International Year of Astronomy press conference at AAS, featuring Galaxy Zoo, coming very soon!
Happening soon here at the AAS meeting…
In a little over an hour, there will be a Galaxy Zoo press conference announcing to the community a new discovery that you have helped make. Many of you have heard about this one in the process of the research coming together, but it is an exciting result.
As always, Astronomy Cast LIVE will be broadcasting the press conference live from here in Pasadena. Here is the link to the live broadcast, which starts at 10:30 AM U.S. Pacific time:
Galaxy Zoo live press conference
During the conference, you will be able to chat, and someone will be on hand to answer any questions that you ask about the research.
After the press conference ends, we will save a recording of the broadcast and keep it available on the same site.
In case any of you have as much trouble as I do with converting time zones in your head (I have missed many a teleconference due to miscalculations), here is the time that it will appear in a major city hopefully near where you are (ordered east to west):
Sydney: 3:30 AM (0330)
Tokyo: 2:30 AM (0230)
Beijing: 1:30 AM (0130)
New Delhi: 11:00 PM (2300)
Moscow: 9:30 PM (2130)
Cape Town: 7:30 PM (1930)
Rome: 7:30 PM (1930)
London: 6:30 PM (1830)
New York: 1:30 PM (1330)
Chicago: 12:30 PM (1230)
Denver: 11:30 PM (1130)
Old galaxies spin in sync
Today’s guest blogger is Raul Jimenez who collaborated with us on an exciting paper on the spin (clockwise vs. counter-clockwise) of spiral galaxies.
The rate at which galaxies transform gas into stars as a function of time gives astronomers insight into the way galaxies formed and evolved. By using the SDSS spectra one can infer the past star formation history of a galaxy. We have been doing this using sophisticated statistical tools, take a look here. Much has been learned about the formation of galaxies using their star formation history, for example we know that the most massive galaxies assemble their stars early on, about 1-2 Gyr after the big-bang while small mass galaxies (100 to 1000 times smaller than the milky way) do it during the whole age of the universe. What we have done in our recent paper is to look at how the star formation history of galaxies correlates to the rotation direction of galaxies as measured by the galaxy zoo project. What we have found is that galaxies that had lots of star formation in the past do tend to rotate in the same direction in groups with lengths of about 10 to 20 Mpc.
Although this might sound surprising, it is not! If one reviews very old papers, almost 40-50 years ago, where people like Andrei Doroskievich worked out the way galaxies should rotate based on how they were formed in the past, one realizes that the correlation we have found arises naturally in these models of galaxy formation, so-called hierarchical models. What is happening is that in the past the cluster of galaxies was not yet formed and the spiral galaxies that the galaxy zoo has been classifying by morphology were coming down the filamentary structure into the proto-clusters. Because the proto-cluster already contains the big elliptical galaxies, they provide the same “pull” on all the spiral galaxies in the filament. So it is quite exciting to see this result from the galaxy zoo and the MOPED/VESPA catalogs. Now it is time to go back to theory and numerical simulations and understand better what it means for galaxy formation and evolution. This is something we will do next.
The paper has been submitted to MNRAS, and the pre-print is available for download on astro-ph.
Galaxy Zoo at AAS meeting next week!
Hi all,
Chris, Pamela, and I will be at the American Astronomical Society meeting next week. As always, I will be liveblogging Zoo-related events at the meeting, and hopefully uploading a photo or two. We’ll be coordinating our coverage with some other bloggers; I’ll post the link to that coverage here tomorrow. And if any of you are in the L.A. area, send me a message on the forum – I would love to meet you.
Summer Mergers at IRAM
Hi All,
As you might recall, we were weathered out last January and so I’ve come back to 1) find my champagne bottle and 2) measure CO gas in merging spirals. The weather has been pretty good so far and in the first two nights we got 9 good detections. I would send pictures of what’s happening here but I forgot my camera cable, so all I can do is send an image of one of our detections. I’ll update you soon!
Good CO Detection
Galaxy Zoo 