ISO/LWS positions observed in [C ii] along the southern part of the major axis of M 33.
ISO/LWS positions observed in [C ii] along the northern part of the major axis of M 33.
Integrated intensities at the positions with [C ii] detections.
The IRAM 30 m CO 2−1 data on the scale were converted into Tmb temperatures using the forward efficiency Feff = 0.90 and the main beam efficiency Beff = 0.49: Tmb = (Feff/Beff) . The CO 2−1 map was first smoothed from the original 11′′ resolution to 22′′ using a Gaussian kernel. To derive CO 1−0 intensities from the CO 2−1 data, we used a linear function of the 2−1/CO 1−0 ratio, which drops from 0.8 in the nucleus of M 33 to 0.5 at a galactocentric distance of 8.5 kpc (Gratier et al. 2010). Next, we smoothed the map to the ISO/LWS resolution and converted the data to intensities in erg cm-2 s-1 sr-1.
Both the H i data and the Hα data were also smoothed to the LWS resolution. The original resolutions of the H i data were 11′′, while we assumed an original pencil beam for the Hα data. Table B.1 lists the resulting integrated intensities of [C ii], H i, Hα, CO 2−1, 1−0, the FIR continuum, and the TIR/FIR ratio for all positions and stacked areas.
We show here four examples of the [C ii] spectra and SEDs obtained. Figure 1a shows the only spectrum with a baseline fit of order one. Figure 1c shows the spectrum from the nucleus, where the lowest rms and highest flux are reached. The highest rms and the lowest flux peak of the four spectra are shown in position N61 (Fig. 1g), which belongs to the northern, outer N2 region. The SEDs show the strongest warm dust component in the nucleus (Fig. 1d), while the weakest warm component is seen in N61 (Fig. 1h). Cold dust components are similar in the inter-arm region (Fig. 1b), the nucleus, and in BCLM302 (Fig. 1f). The outer points also show weaker cold dust emission than the other regions.
Examples of some of the [C ii] ISO/LWS spectra and SEDs obtained in this work. The vertical dashed lines mark the integration interval to derive the FIR continuum, 42.5 μm and 122.5μm (Dale & Helou 2002). a), b) The first row shows the [C ii] spectrum and the SED of the inter-arm position S32. c, d) The second row shows the spectrum and SED from the nucleus of M 33. e), f) The third row shows observations of the H ii region BCLMP 302 (N49). g), h) Finally, the last row shows the spectrum and the SED from one of the positions (N61) in the outer, southern N2 region. The SEDs show MIPS 24 μm and 70 μm, PACS 100 μm and 160 μm and SPIRE 250 μm, 350 μm and 500 μm data. In the [C ii] spectra, green lines show Gaussian fits to the spectra and blue lines show fitted baselines.
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[C ii] versus CO, which is normalized using the total infrared continuum (TIR). Big green filled circles show ISO/LWS data of the inner S1, N1 regions of M 33, while open circles show data of the outer S2, N2 regions. The lowest [C ii]/CO ratio observed with ISO/LWS in M 33 is 1000 (lower blue dashed line), while the highest ratio is 41 200 (upper blue dashed line). Black solid and dotted lines indicate lines of constant density n and FUV field G0, respectively, from the standard K99 PDR model with AV = 10 mag and solar metallicity Z = 1.
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© ESO, 2013