3 Results

Figure 1: The CO $J=1\rightarrow 0$ results. Here and in Figs. 2, 3 and 4 the intensity scale is $T_{\rm A}^*$ and the velocity resolution is shown above each scan

Figure 1: continued

Figure 1: continued

Figure 1: continued

Figure 2: The CO $J=2\rightarrow 1$ results

Figure 2: continued

Figure 3: The HCN $J=1\rightarrow 0$ results

Figure 3: continued

Figure 3: continued

Figure 4: The CS $J=3\rightarrow 2$ results

Upon comparison of the CO detections (Figs. 1 and 2) with those from previous surveys (Heckman et al. 1989; Maiolino et al. 1997; Papadopoulos & Seaquist 1998), we find that, for the most part, we have similar results with the following exceptions: CO  $1\rightarrow 0$ in NGC 1365 is similar to that of Maiolino et al. (1997); Papadopoulos & Seaquist (1998), although more symmetric than the detection of Heckman et al. (1989). Our $2\rightarrow 1$ detection is not as symmetric as that of Papadopoulos & Seaquist (1998) and since the profile of Sandqvist et al. (1995) is also quite symmetrical we attribute our asymmetry to a pointing error. In NGC 1667 the profile is identical in shape to that of Heckman et al. (1989) but reflected with the peak occurring at the minimum, as opposed maximum velocity. In the case of Maiolino et al. (1997); Papadopoulos & Seaquist (1998), the peak also occurs at the maximum although these are somewhat more symmetric, indicating that we have a pointing error. NGC 5033; our detection appears to be somewhat skewed compared with those of Heckman et al. (1989); Maiolino et al. (1997); Papadopoulos & Seaquist (1998), although of a similar integrated intensity. NGC 5548; undetected by Heckman et al. (1989) and not observed by Papadopoulos & Seaquist (1998), our detection has a somewhat wider profile than that of Maiolino et al. (1997). The results of the observations are summarised in Table 2, where the upper limits for HCN $1\rightarrow 0$ and $3\rightarrow2$ are over the velocity range of the CO $1\rightarrow 0$ detections.

 

 

Table 2: The 18 Seyfert galaxies detected in CO  $1\rightarrow 0$ by Heckman et al. (1989) hbw+89 plus two non-detections (, selected in order to provide a more balanced sample of type 1 and type 2 Seyferts) which are observable from OSO and SEST (Teles.). In this table Sy refers to the (intermediate; Osterbrock 1981) Seyfert type and v is the heliocentric radial velocity (NASA/IPAC Extragalactic Database). The final columns refer to the main-beam brightness temperature, $I_{\rm mb}$, [K km s^-1] measured for the corresponding transition, where the results have been rounded to two figures (because of $\eta _{\rm mb}$) and the errors and upper limits are according to $1\sigma$ (defined by the noise). The "New'' column indicates whether these are first time detections in the HCN  $1\rightarrow 0$ transition for these galaxies

Galaxy	Sy	v [km s-1]	Teles.	CO  $1\rightarrow 0$	CO  $2\rightarrow 1$	HCN  $1\rightarrow 0$	New	CS  $3\rightarrow2$
NGC 0034	2	5931	SEST	10(1)	18(1)	1.6(0.2)		<1
NGC 0931	1.5	5001	OSO	0.5(0.4)	-	<0.8		-
NGC 1068	2	1134	OSO	86(3)	-	11(1)		-
NGC 1365	1.8	1636	SEST	97(1)	110(1)	6.0(0.1)		6.3(0.3)
NGC 1667	2	4547	OSO	15(1)	-	3.5(0.5)	$\surd$	-
UGC 03374/MCG 08-11-011	1.5	6141	OSO	2.8(0.3)	-	<0.2		-
NGC 2273	2	1840	OSO	3.2(0.3)	-	0.5(0.3)	$\surd$	-
Mrk 10/UGC 04013	1	8770	OSO	1.0(0.3)	-	<0.3		-
NGC 4593	1	2698	SEST	1.7(0.4)	2.2(0.3)	-		-
Mrk 231/UGC 08058	1	12651	OSO	10(1)	-	1.0(0.2)		-
NGC 5033	1.9	875	OSO	32(2)	-	1.7(0.3)	$\surd$	-
Mrk 273/UGC 08696	2	11318	OSO	5(1)	-	3(1)	$\surd$	-
NGC 5135	2	4112	SEST	18(1)	25.8(0.6)	0.65(0.07)	$\surd$	<1
NGC 5347	2	2336	OSO	1.3(0.5)	-	<0.3		-
NGC 5548	1.5	5149	SEST	2.4(1.2)	7.0(0.4)	-		-
Arp 220	2	5314	OSO	12(1)	-	2.4(1.0)		-
NGC 6814	1.5	1563	SEST	7.2(0.1)	3.9(0.1)	0.45(0.08)	$\surd$	<1
NGC 7130/IC 5135	2	4842	SEST	17(1)	26(1)	0.7(0.1)		<1
NGC 7172	2	2603	SEST	5.1(0.9)	7.3(0.3)	-		-
NGC 7469	1.2	4889	OSO	22(1)	-	1.7(0.4)		-

The luminosities according to the integrated intensity over the projected beam area are shown in Table 3.

 

 

Table 3: The observed luminosities of the sample. $L_{{\rm CO}~1\rightarrow0}$, $L_{{\rm CO}~2\rightarrow1}$, $L_{{\rm HCN}~1\rightarrow0}$ and $L_{{\rm CS}~3\rightarrow2}$ refer to the luminosity over the HPBW for each respective transition, again with $1\sigma$ errors and upper limits [ $\times 10^{3}$ K km s^-1 kpc²]. Like Heckman et al. (1989) we have calculated the physical beam area by using the distances given by heliocentric radial velocities (Table 2) and assuming the same Hubble parameter as before, except in the case NGC 1365 where the assumed distance of 20 Mpc, to the Fornax cluster, is used. The $\int L_{{\rm CO}~1\rightarrow0}$ refers to the global CO  $1\rightarrow 0$ luminosity [ $\times 10^{3}$ K km s^-1 kpc²]: ^aPlanesas, Gomez-Gonzalez & Martin-Pintado (1989) (over a partial map spanning ( $120''\times 120''$), ^bYoung et al. (1995), ^cSandqvist et al. (1995) (over $204''\times 164''$) and ^dBryant & Scoville (1996). Although apparently high, the CO luminosity in NGC 1068 (Young et al. 1995) is similar to that obtained from a large scale map of the Circinus galaxy (Curran 2000b; Curran et al. 2000). $L_{\rm FIR}$ [ $10^{10}~L_{\odot}$] refers to the far infrared luminosity computed using the FIR flux (Lonsdale et al. 1985; Heckman et al. 1989). The CO $2\rightarrow 1$ (CO intensity ratios) and CS results are discussed in Curran (2000b)

Galaxy	Sy	$L_{{\rm CO}~1\rightarrow0}$	$\int L_{{\rm CO}~1\rightarrow0}$	$L_{{\rm CO}~2\rightarrow1}$	$L_{{\rm HCN}~1\rightarrow0}$	$L_{{\rm CS}~3\rightarrow2}$	$L_{\rm FIR}$
NGC 0034	2	$2.3\pm0.1$	-	$0.28\pm0.01$	$0.56\pm0.07$	<0.1	14.3
NGC 0931	1	$0.08\pm0.04$	-	-	<0.1	-	2.1
NGC 1068	2	$0.42\pm0.01$		-	$0.09\pm0.01$	-	7.4
NGC 1365	2	$1.5\pm0.1$	5.3c	0.48	$0.16\pm0.03$	$0.063\pm0.006$	6.8
NGC 1667	2	$1.18\pm0.08$	-	-	$0.45\pm0.06$	-	4.2
UGC 03374	1	$0.40\pm0.04$	-	-	<0.05	-	2.9
NGC 2273	2	$0.041\pm0.003$	$0.38\pm0.07^b$	-	$0.008\pm0.004$	-	0.66
Mrk 10	1	$0.3\pm0.1$	-	-	<0.1	-	2.7
NGC 4593	1	$0.08\pm0.02$	-	$0.025\pm0.003$	-	-	0.79
Mrk 231	1	$6.0\pm0.6$	5d	-	$1.0\pm0.2$	-	128
NGC 5033	2	$0.093\pm0.006$	$10\pm3^b$	-	$0.014\pm0.002$	-	0.53
Mrk 273	2	$2.4\pm0.4$	-	-	$2.4\pm0.8$	-	73
NGC 5135	2	$2.0\pm0.1$	-	$0.69\pm0.02$	$0.11\pm0.01$	<0.06	9.0
NGC 5347	2	$0.03\pm0.01$	-	-	<0.01	-	0.28
NGC 5548	1	$0.4\pm0.2$	-	$0.29\pm0.02$	-	-	0.86
Arp 220	2	$2.6\pm0.1$	-	-	$0.4\pm0.2$	-	84
NGC 6814	1	$0.118\pm0.002$	$0.38\pm0.06^b$	0.015	$0.011\pm0.002$	<0.01	0.66
NGC 7130	2	$2.6\pm0.2$	-	0.96	$0.16\pm0.02$	<0.03	11.9
NGC 7172	2	$0.23\pm0.04$	-	$0.19\pm0.01$	-	-	1.2
NGC 7469	1	$2.00\pm0.09$	$1.9\pm0.3^b$	-	$0.25\pm0.07$	-	18.2

 

 

Table 4: The approximate observed CO $1\rightarrow 0$/HCN $1\rightarrow 0$ luminosity ratios

Galaxy	Sy	$\frac{L_{\rm CO}}{L_{\rm HCN}}$	Published intensity ratios
NGC 0034	2	4	-
NGC 0931	1		-
NGC 1068	2	5	9 (Helfer & Blitz 1993)
NGC 1365	2	9	-
NGC 1667	2	3	-
UGC 03374	1		-
NGC 2273	2	5	-
Mrk 10	1		-
Mrk 231	1	6	4.2 (SDR92)
NGC 5033	2	7	-
Mrk 273	2	1	-
NGC 5135	2	18	-
NGC 5347	2		-
Arp 220	2	7	8 (SDR92)
NGC 6814	1	11	-
NGC 7130	2	16	13 (Aalto et al. 1995)
NGC 7469	1	4	10 (Bryant 1997)

Testing our global results, initially we obtained a fair linear fit by plotting $\ln L_{{\rm CO}}$ against $\ln L_{{\rm HCN}}$ for the sample galaxies with recessional velocities exceeding 4000 km s^-1. This corresponds to a HPBW of $\approx12$ kpc (at SEST, $\approx10$ kpc at OSO), beyond which there is expected to exist little molecular gas (Maiolino et al. 1997). Plotting $\log L_{{\rm CO}}$ against $\log L_{{\rm HCN}}$ for all of the sample, however, Fig. 5, we see that we obtain the same linear relationship between the CO and HCN luminosities.

Figure 5: $\log L_{{\rm CO}}$ versus $\log L_{{\rm HCN}}$ (units as in Table 3, i.e. $\times10^{3}$ K km s-1 kpc2) for all the detections. From these we obtain a ratio of $L_{\rm CO}/L_{\rm HCN}=6^{+5}_{-3}$ and using only sources with  km s-1, we obtain a ratio of $L_{\rm CO}/L_{\rm HCN}=6^{+7}_{-3}$

From the intercept of the log plot, we estimate the $L_{\rm HCN}$ to $L_{\rm CO}$ ratio for the sample to be similar to the value determined for the ULIRGs (SDR92; Bryant 1997). It is interesting that this relationship holds true for both the distant (  km s^-1) and near-by (  km s^-1) sources, as it implies that the global CO/HCN luminosity ratio for distant sources $\approx$ the central ratio for near-by sources $\approx6$. If we plot the global CO values from the literature, Table 3, against the observed HCN luminosities we obtain a ratio of $L_{\rm CO}/L_{\rm HCN}=17^{+15}_{-8}$.

Figure 6: $\log L_{{\rm FIR}}$ [$L_{\odot }$] versus $\log L_{{\rm HCN}}$ [K km s-1 pc2] for all the detections

In order to determine the far infrared/HCN luminosity correlation, i.e. compare our results with those of SDR92, we plotted $\log L_{{\rm FIR}}$ against $\log L_{{\rm HCN}}$, for all of the sources, Fig. 6. Here we see that we again obtain a fair linear relationship between the FIR and the HCN luminosities and from this we determine $L_{\rm FIR}\approx600^{+600}_{-300}\ L_{\rm HCN}~L_{\odot}({\rm K ~km~s}^{-1}~{\rm pc}^2)^{-1}$.