 Arecibo Galaxy
Environment Survey (AGES) |
M74 (NGC 628) GROUP OBSERVATIONS
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RESULTS!
The M74 group is a gas-rich galaxy group located at roughly 10 Mpc and
is
similar in makeup to the Local Group. M74 dominates the surrounding
region
and is accompanied by several dwarf galaxies, some of which are
star-forming.
M74 and three of these dwarfs (UGC 1776, UGC 1771 and KDG 010) lie
within
a 5° x 1° strip making it an ideal test region for the AGES
drift
mapping region.
Above: False colour DSS image of M74 with two of the closest dwarfs, UGC 1771 and UGC 1176
Observing Strategy:
We have decided upon a drift mapping approach to scan the entire region. We have defined 5 constant declination scans 5° in length, separated by approximately one full ALFA footprint. In order to fully sample the sky we have decided to perform a second run, offset from the first by half a beam width in declination. These two patterns ('a' & 'b') are then repeated throughout the observing run.
Above: The 'a' scans with the positions of the galaxies
superimposed.
The solid lines represent the central beam tracks and the dashed lines
represent
the tracks of outer beams once ALFA is rotated to get even beam
separation.
The scans are numbered 1-5 starting with the highest scan.
Below: The same as above with the 'b' scans added. The
central beam tracks
are again shown with solid lines but the outer beams of the 'b' scans
are represented by dotted lines.
This observing strategy is complicated by the fact that we can't observe all our strips as they transit. Because we are observing off-meridian we need to calculate the angle ALFA needs to be rotated for each strip in order to maintain equal separation between the beams. Thanks to collaboration between the Cornell and Cardiff groups there are now a set of IDL routines that can calculate this angle and Robert 'Bobby' Minchin is working on widgetising them.
Observing schedule:
| DATE |
START
TIME (AST) |
END
TIME (AST) |
START
TIME (LST) |
END
TIME (LST) |
M74 HA
AT START |
M74 HA
AT END |
| 19/11/04 |
21:15 |
23:45 |
00:46 |
03:16 |
-0:51 |
1:39 |
| 20/11/04 |
21:15 |
23:45 |
00:50 |
03:20 |
-0:47 |
1:43 |
| 21/11/04 |
21:15 |
23:45 |
00:53 |
03:25 |
-0:44 |
1:47 |
| 22/11/04 |
21:00 |
23:30 |
00:42 |
03:13 |
0:55 |
1:36 |
| 23/11/04 |
21:00 |
22:45 |
00:46 |
02:31 |
-0:51 |
0:55 |
| 24/11/04 |
21:00 |
22:45 |
00:50 |
02:35 |
-0:47 |
0:58 |
| 25/11/04 |
21:00 |
22:45 |
00:55 |
02:39 |
-0:43 |
1:03 |
| 28/11/04 |
20:45 |
22:30 |
00:51 |
02:36 |
-0:46 |
0:59 |
| 29/11/04 |
20:30 |
22:15 |
00:39 |
02:25 |
-0:57 |
0:48 |
| 30/11/04 |
20:30 |
22:15 |
00:44 |
02:29 |
-0:53 |
0:52 |
| 01/12/04 |
20:30 |
22:15 |
00:48 |
02:33 |
-0:49 |
0:56 |
| 02/12/04 |
20:30 |
22:15 |
00:52 |
02:37 |
-0:45 |
1:00 |
| 03/12/04 |
20:15 |
22:00 |
00:40 |
02:26 |
-0:56 |
0:49 |
| 04/12/04 |
20:15 |
22:00 |
00:44 |
02:30 |
-0:52 |
0:53 |
| 05/12/04 |
20:15 |
22:00 |
00:48 |
02:34 |
-0:48 |
0:57 |
| 13/12/04 |
19:45 |
22:00 |
00:50 |
03:05 |
-0:47 |
0:57 |
| 14/12/04 |
19:30 |
22:00 |
00:39 |
03:09 |
-0:58 |
01:32 |
| 15/12/04 |
19:30 |
21:45 |
00:42 |
02:58 |
-0:54 |
01:21 |
| 16/12/04 |
19:30 |
21:45 |
00:47 |
03:02 |
-0:50 |
01:25 |
| 17/12/04 |
18:30 |
21:45 |
00:51 |
03:06 |
-0:46 |
01:29 |
| 18/12/04 |
19:15 |
21:30 |
00:39 |
02:55 |
-0:57 |
01:18 |
Scan Strategy:
DUE TO THE TIME SLOTS WE ONLY HAVE TIME TO DO ONE SCAN BEFORE TRANSIT. WE HAVE DECIDED THAT THE MOST IMPORTANT SCAN IS THE CENTRAL ONE AND HAVE REORGANISED THE SCAN ORDER SO THAT THIS STRIP IS OBSERVED AT TRANSIT. ALL RUNS BEGIN WITH STRIP 2. FOR THE SHORTER SLOTS WE WILL HAVE TO SACRIFICE ONE OR TWO SCANS.| Scan |
HA |
AZ |
ALFA
ANGLE |
Beam
Separation
(arcmin) |
LST range of drift |
|
| 2a |
-0:25 |
289.75 |
84.0 |
1.84 |
01:04:17 |
01:24:17 |
| 2b |
-0:25 |
289.88 |
83.8 |
1.84 |
01:04:17 |
01:24:17 |
| 3a |
0:00 |
-0.62 |
19.3 |
2.08 |
01:29:17 |
01:49:17 |
| 3b |
0:00 |
-0.62 |
19.3 |
2.08 |
01:29:17 |
01:49:17 |
| 4a |
0:25 |
66.01 |
-41.7 |
1.85 |
01:54:17 |
02:14:17 |
| 4b |
0:25 |
65.89 |
-41.7 |
1.85 |
01:54:17 |
02:14:17 |
| 5a |
0:50 |
77.70 |
-53.0 |
1.82 |
02:19:17 |
02:39:17 |
| 5b |
0:50 |
77.63 |
-52.9 |
1.82 |
02:19:17 |
02:39:17 |
| 1a |
1:15 |
85.92 |
-60.2 |
1.80 |
02:44:17 |
03:04:17 |
| 1b |
1:15 |
85.87 |
-60.2 |
1.80 |
02:44:17 |
03:04:17 |
This webpage was written by Robbie Auld, Cardiff University, UK. Last updated 20/01/2005.