Galaxy Groups

[orionbelt]

Hello Greg,

I am working on some observing list for galaxy trios and galaxy groups. I found out that some trios are in my Supplemental Database, maybe I put them there years ago and I don´t remember or were imported form some observing list. I had been importing my data from ST2 to 3 and then to 4 so I am not sure where they are coming from.

With galaxy groups that are in the database like Hickson, ST can calculate the difficulty and other conditions, the magnitude is usually the brightest member magnitude and there is the size of the group and the number of members. It's possible to include those in the groups or trios entered in the supplemental database? Can it calculate the visibility just with the magnitude and knowing that is a group of galaxies, by an approximate superficial luminosity estimation?

Any suggestions about how to get sky tools to estimate visibility of galaxy groups that are not in the database as groups, the galaxies are there thought, but other that including the members one by one, which was my approach in the past.

Thanks. Clear skies,

Carles

[theskyhound]

Hello Carles,

Thanks for bringing this up. The first thing to do is to make sure that the galaxy group isn't in the latest database. To do that, open it in the atlas and have a look for it. You may need to increase the magnitude limit for galaxy groups. Be sure to check that your supplemental database object is at the right position, using something like SIMBAD or NED, if you don't see any galaxies at that location. If it does show up in the regular database, then replace the supplemental database object with the regular database object in your lists. Its more difficult if you have logs for it. You may need to copy the log data to a temporary text file and then create a new log entry for the object from the regular database using that previous info.

As far as calculating the visibility for supplemental database objects, there isn't a good way to do that. There is not enough information included. The presumption is that supplemental database objects are there for very rare cases where the object isn't in the database. Be sure to report the missing object to me, providing the designation and RA/Dec, so I can make sure to add it in the future.

[theskyhound]

One thing you could do is to find the brightest galaxy in the group and put that in the list so SkyTools can do the calculations for it and then use those.

[orionbelt]

Thank you, that looks like good ideas.