Arecibo L-band Feed ArrayArecibo Galaxy Environment Survey (AGES)

M74 (NGC 628) GROUP OBSERVATIONS

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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.



M74 and a couple of dwarfs

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.

SCAN STRATEGY

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.

scan strategy 2

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.