Calibrators at 235 MHz

The list of the sources taken for this project are the calibrators at 1420 MHz for VLA and not at 325 MHz for VLA. So we didn't expect the observed sources to be very good calibrators at 235 MHz. With the defined criteria in the previous section (Flux density $>$ 2.5 Jy and no secondary source greater than 10% of flux density of the calibrator), we have found only 3 calibrators as good calibrators, listed in the table 4.3, List 1 as Class A.

However, to give some additional information, we have given 4 tables where we have relaxed the defined criteria in various ways and given the astronomer the freedom of choice. The selection criteria for the for the 4 categories are given below.

We have defined a list of Class B calibrators where we have relaxed the limit on the secondary sources in the field allowing it to be as high as 25%. There are 10 sources in this category which are listed in Table 4.4, List 2 as Class B calibrators. Next, we have defined another list of Class C calibrators where we have put the limit as addition of the peak flux density of the source and flux density of the first secondary source is greater than 3 Jy and flux density is the second secondary source is less than 10% of the peak flux denisty. There are 7 sources in this category which are listed in Table 4.5, List 3 as Class C calibrators. And at last, we have defined another list of Class D calibrators where we have put the limit as addition of the peak flux density of the source and flux density of the first secondary source is greater than 3 Jy and flux density is the second secondary source is less than 25% of the peak flux denisty. There are 14 sources in this category which are listed in Table 4.6, List 4 as Class D calibrators.

• Class A - List 1 : The table 4.3 lists the sources as GMRT calibrators for which, the flux density (both peak as well as integrated) is greater than 2.5 Jy and the flux density of secondary source is less than 10% the flux density of the source. There are 3 sources in this category

• Class B - List 2 : The table 4.4 lists the sources as GMRT calibrators for which, the flux density (both peak as well as integrated) is greater than 2.5 Jy and the flux density of secondary source is greater than 10% and less than 25% the flux density of the source.

• Class C - List 3 : The table 4.5 lists the sources as GMRT calibrators for which, the addition of peak flux density and flux density of first secondary source is greater than 3 Jy and flux density of second secondary source is less than 10% of the peak flux density.

• Class D - List 4 : The table 4.6 lists the sources as GMRT calibrators for which, the addition of peak flux density and flux density of first secondary source is greater than 3 Jy and flux density of second secondary source is greater than 10% and less than 25% of the peak flux density.

Table 4.3: (Class A - List 1) : Identified Calibrators for GMRT at 235 MHz (Flux Density of Secondary Source is $<$ 10% of that of Primary Source.)

Sr.	Source	Flux	Sr.	Source	Flux	Sr.	Source	Flux
No.	Name	Density	No.	Name	Density	No.	Name	Density
	(J2000)	(Jy.)		(J2000)	(Jy.)		(J2000)	(Jy.)
1.	0432+416	14.43	2.	0447-220	4.28	3.	1154-350	9.42

Table 4.4: (Class B - List 2) : Identified Calibrators for GMRT at 235 MHz (Flux Density of Secondary Source is $>$ 10% and $<$ 25% of that of Primary Source.)

Sr.	Source	Flux	Sr.	Source	Flux	Sr.	Source	Flux
No.	Name	Density	No.	Name	Density	No.	Name	Density
	(J2000)	(Jy.)		(J2000)	(Jy.)		(J2000)	(Jy.)
1.	0119+321	3.61	4.	0538-440	3.11	7.	0837-198	9.94
2.	0323+055	5.99	5.	0607-085	2.82	8.	1313+675	6.24
3.	0440-435	5.62	6.	0834+555	6.65	9.	1323-448	3.48
-	-	-	-	-	-	10.	1448-163	2.88

Table 4.5: (Class C - List 3) : Identified Calibrators for GMRT at 235 MHz (Flux Density of Second Secondary Source is $<$ 10% of that of (Primary Source $+$ First Secondary Source).)

Sr.	Source	Flux	Sr.	Source	Flux	Sr.	Source	Flux
No.	Name	Density	No.	Name	Density	No.	Name	Density
	(J2000)	(Jy.)		(J2000)	(Jy.)		(J2000)	(Jy.)
1.	0119+321	3.61	4.	0447-220	4.28	7.	2344+824	3.50
2.	0323+055	5.99	5.	1154-350	9.42	-	-	-
3.	0410+769	7.78	6.	1330+251	18.67	-	-	-

Table 4.6: (Class D - List 4) : Identified Calibrators for GMRT at 235 MHz (Flux Density of Second Secondary Source is $>$ 10% and $<$ 25% of that of (Primary Source $+$ First Secondary Source).)

Sr.	Source	Flux	Sr.	Source	Flux	Sr.	Source	Flux
No.	Name	Density	No.	Name	Density	No.	Name	Density
	(J2000)	(Jy.)		(J2000)	(Jy.)		(J2000)	(Jy.)
1.	0155-408	2.41	6.	0607-085	2.82	11.	0943-083	2.68
2.	0237+288	2.12	7.	0632+103	2.17	12.	1313+675	6.24
3.	0438+488	1.89	8.	0834+555	6.65	13.	1323-448	3.48
4.	0440-435	5.62	9.	0837-198	9.94	14.	1448-163	2.88
5.	0538-440	3.11	10.	0902-142	3.99	-	-	-