2 Observations and data reduction

The data presented here are part of the MPE ISO Guaranteed time project "Bright Galactic Nuclei". The observations were carried out throughout the ISO mission and were all taken in the standard AOT SWS02 mode, i.e. grating line profile scan. The SWS has three different apertures with dimensions (projected on the sky) ap1: $14''\times20''$, ap2: $14''\times27''$ and ap3: $14''\times20''$. The following molecular transitions (and the corresponding apertures) were observed although not in all sources: (1-0)Q(3) (ap1), (0-0)S(0) (ap3), (0-0)S(1) (ap2), (0-0)S(2) (ap1), (0-0)S(3) (ap3), (0-0)S(5) (ap2), and (0-0)S(7) (ap2). The sample targets are presented in Tables 1 and 2 for the starbursts and Seyferts, respectively. Galaxy names, distances (assuming H ₀ = 75 km s^-1 Mpc^-1), extinction towards the ionized medium, and comments are also listed. We note that the SWS aperture sizes are most likely larger than the presumed sizes of the circumnuclear regions for a large fraction of the present samples of Starburst and Seyfert galaxies.

   

Table 1: The Starburst sample galaxies.

Galaxy Name	D	A V 1	Spec. type	comments
	Mpc	[mag]
NGC 253	3.5	30	HII, SB	Sc, edge-on
IC 342	3.6	12	HII, SB	Scd, face-on
II Zw 40	7	32	HII	BCD
M 823	3.3	10	HII, SB	Irr
NGC 3256a	36.6	35	SB	colliding pair
NGC 3690A/BC3	40	20	SB	pec. merger
NGC 4038/393,b	21.0	80	SB	interacting
NGC 4945c	4	20	SB, Sy2	Sc edge-on
NGC 5236 (M 83)	5.0	5	HII, SB	SAB(s), face-on
NGC 5253	4.1	14	HII, SB	Im pec
NGC 6946d	5.7	1.84	HII	S(AB)cd,face-on
NGC 7552	21.2	5	HII, LINER	SA(c), face-on

¹ A_V from Genzel et al. (1998).
² A_V (screen) from Baldwin et al. (1982).
³ The ISO pointings on these galaxies are as follows (J2000): M 82:00 39 43.38, 69 40 44.4, NGC 3690A: 11 45 54.24, 58 33 46.5, NGC 3690BC: 11 45 54.06, 58 33 45.6, NGC 4038/39:00 48 07.66, -18 53 04.1. The ISO pointings for the remaining galaxies are on the galaxy's nucleus.
⁴ A _V (screen) from Hyman et al. (2000).
^a Rigopoulou et al. (1996), ^b Kunze et al. (1996), ^c Spoon et al. (2000), ^d Valentijn et al. (1996).

The data were reduced using the Interactive Analysis (IA) Package of the SWS team including sophisticated tools to improve cosmic ray hit removal, dark subtraction, defringing and flat-fielding. The flux calibration is accurate to about 25% (Schaeidt 1996). The calibration files of June 2000 were used.

Figures 1 and 2 show the observed H₂ molecular lines in starburst and Seyfert galaxies. In almost all cases the S(1) and S(5) lines are clearly detected in both the Seyfert and the Starburst samples. Tables 3 and 4 give the actual line flux values for starbursts and Seyferts, respectively.

From the sample of 13 starbursts (the two components in NGC 3690 have been observed separately) the S(0) line was observed in 10 of them and detected in 5. The S(0) line was observed in all (9) Seyferts and detected in 4 of them.

Figure 1: H2 molecular lines from starbursts: from left to right (1-0)Q(3), (0-0)S(7), (0-0)S(5), (0-0)S(3), (0-0)S(2), (0-0)S(1) and (0-0)S(0). The vertical axis is Flux in Jy, the horizontal axis is wavelength in $\mu$m. Note: previously published spectra for NGC 3256, NGC 4038 and NGC 4945 and NGC 6946 are not included in this figure.

Figure 2: H2 molecular lines in Seyferts. The spectral lines from the various transitions and the axes are the same as in Fig. 1.

For those sources where lines were not detected we quote "good confidence'' upper limits. As mentioned earlier a large number of atomic and ionic lines were observed for each source. For the purpose of the current paper we focus on the H₂ emission. More detailed analysis for some of the sources can be found in other papers (NGC 4038/39: Kunze et al. 1996; NGC 3256: Rigopoulou et al. 1996; NGC 4151: Alexander et al. 1998; Sturm et al. 1998; Circinus: Moorwood et al. 1996; NGC 1275: Krabbe et al. 2000; NGC 1068: Lutz et al. 2000).