Need Data to calculate hubble constant!

[jurgens]

Hi, I was wondering if any one can point me to a data file or a webstie that has a list of the distances to a galaxy from Cepheid or RR Lyrae stars and the radial velocity of those galaxies. Or data that will allow me to calculate those two values, ie the spectrum for the stars, or the period/magnitude calculations for the cepheids in the galaxies. I need this because I want to do a plot of this data to do a calculation of the hubble constant.<br /><br />If any of you know somewhere that would have this information in an excel file, or a .dat/.txt file could you please link it for me?<br /><br />Thanks!

 

[thalion]

Your best bet would be to look up familiar galaxies and their data on SIMBAD, which also has links to many abstracts with the latest findings on the galactic distances.<br /><br />SIMBAD:<br />http://simbad.u-strasbg.fr/Simbad<br /><br />For instance, pick a familiar galaxy like M51 or M104, or a slightly more obscure one like NGC 1275.<br /><br />Then use the Extragalactic Database, also known as NED for further data:<br />http://nedwww.ipac.caltech.edu/<br /><br />With these, and the latest findings about the Hubble Constant on the Web, you should do all right.<br /><br />Good luck.

 

[jurgens]

ohh man thanks a lot!<br /><br />I completely forgot about simbad <img src="/images/icons/blush.gif" />ops: Also, I managed to find on that caltech website the The Hubble Space Telescope Key Project on the Extragalactic Distance Scale, so I am going to use the Cepheid data from there to calculate distances, and the radial velocites from simbad.

 

[thalion]

Welcome. <img src="/images/icons/smile.gif" />

 

[jurgens]

Done! boy was that tedious, lots of formulas for excel, but its done, I got a value of about 73.238. That accepted value for the hubble constant right now is 71 +/- 4, so I am right in the error margin =)

 

[vogon13]

Those of us who are math impaired salute you!<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[Saiph]

Jurgen, any chance you can give more details of the process? I know how you calculate it, but others may not.<br /><br />Also, I may not realize some of the hurdles you had to deal with (as you mentioned lots of calculations and I can only think of a small handful) <div class="Discussion_UserSignature"> <p align="center"><font color="#c0c0c0"><br /></font></p><p align="center"><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">----</font></em></font><font color="#666699">SaiphMOD@gmail.com </font><font color="#999999"><em><font size="1">-------------------</font></em></font></p><p><font color="#999999"><em><font size="1">"This is my Timey Wimey Detector.  Goes "bing" when there's stuff.  It also fries eggs at 30 paces, wether you want it to or not actually.  I've learned to stay away from hens: It's not pretty when they blow" -- </font></em></font><font size="1" color="#999999">The Tenth Doctor, "Blink"</font></p> </div>

 

[jurgens]

Sure,<br /><br />http://www.geocities.com/jurgenshestani/hubble.html<br /><br />I had to retype my .doc file for the website heh.<br /><br />The zip file is orgranized like this, there is one folder per galaxy, each galaxy has 2 files. One is the .dat file taken from the hubble key project and it contains photometry data for a group of Cepheids, the other file is an excel spreadsheet containg two sheets. One sheet is the raw data imported into excel, and the other sheet is the period and apparent v-band magnitude, I calcualted the distance using this data.