A&A 414, 141–153 (2004) Astronomy DOI: 10.1051/0004-6361:20031634 & c ESO 2004 Astrophysics Cold dust and molecular gas towards the centers of Magellanic type galaxies and irregulars, I. The data M. Albrecht1,R.Chini1,E.Kr¨ugel2,S.A.H.M¨uller1,andR.Lemke1 1 Astronomisches Institut der Ruhr-Universit¨at Bochum, Universit¨atsstr. 150, 44780 Bochum, Germany e-mail: [email protected] 2 Max Planck Institut f¨ur Radioastronomie Bonn, Auf dem H¨ugel 69, 53121 Bonn, Germany Received 29 July 2003 / Accepted 16 October 2003 Abstract. We present 1300 µm continuum emission measurements and observations of the 12CO (1–0) and (2–1) transition towards the centers of 64 Magellanic type galaxies (Sdm/Sm) and irregulars (Im/I0/Irr). The sources are selected to have 12 IRAS flux densities S 100 µm ≥ 1000 mJy and optical diameters mainly below 180 . We were able to detect CO towards 41 and the continuum emission towards 28 galaxies. In addition, we obtained the corresponding data for a set of 6 complementary galaxies of different morphological type. Key words. galaxies: interstellar matter – galaxies: abundances – galaxies: Magellanic type – radio lines: galaxies – radio continuum: galaxies 1. Introduction comparison of the two independent tracers of the amount of molecular gas. Among the various constituents of the interstellar matter (ISM) While similar studies have been conducted for galaxies of the amount of dust and molecular gas are decisive quantities Hubble type S0 to Sd (Chini et al. 1996; Kr¨ugel et al. 1988a, for our understanding of galaxy evolution, chemistry and star 1988b, 1990), no systematic approach to observe dust as well formation processes. As H2 lacks a permanent electric dipole as molecular gas towards Magellanic type dwarfs with the same moment and its emission arises only from hot or warm gas, beam size has been made so far. The presented measurements absorption measurements against strong far-ultraviolet back- will allow a comparison with galaxies of earlier Hubble type as ground sources or indirect methods are used to estimate the regards their properties derived from mm observations. mass of the cold molecular component of the ISM. The most In the following we describe the observational setups and widely applied indirect methods consider the CO line emission the data reduction. We present the resulting flux densities of the or the dust mass as tracers. Dust itself is of special interest as it 1300 µm continuum emission. Furthermore, we show the ob- is strongly linked to star formation. It has the property of being tained 12CO spectra and list the corresponding line parameters. very sensitive to the ultraviolet radiation of young massive stars For a set of galaxies the 12CO lines led to independent distance and re-radiates it from infrared to mm wavelengths. A main estimates which in conjunction with data from the literature 12 goal of this study is to obtain measurements of the CO line were used to newly derive H and optical properties of the ob- µ transitions and the continuum emission at 1300 m at an iden- jects. The data will be discussed in detail elsewhere (Albrecht tical or at least similar spatial resolution. This does not only et al., in prep.). facilitate a reliable correction of the continuum emission for line contamination but – more importantly – allows a direct 2. Galaxy sample Send offprint requests to: M. Albrecht, Our galaxy sample contains 31 Magellanic type spirals e-mail: [email protected] (Sdm, Sm), 30 Magellanic irregulars (Im) and 3 irregulars Based on observations collected at ESO, La Silla, Chile and (I0, Irr) according to the classification of de Vaucouleurs IRAM, Pico Veleta, Spain. et al. (1991, hereafter RC3). The objects have been taken The full version of Figs. 3 and 4 is only available in electronic from the compilation of morphological dwarf galaxies with form at http://www.edpsciences.org known optical magnitudes, optical sizes and H fluxes by Article published by EDP Sciences and available at http://www.aanda.org or http://dx.doi.org/10.1051/0004-6361:20031634 142 M. Albrecht et al.: Dust and molecular gas in Magellanic type galaxies and irregulars. I. Table 1. The Sdm/Sm sample. Name Name RA Dec D Angular d25 S 100 µm logMH i MB Morph. Type (J2000.0) (J2000.0) Size (IRAS) [Mpc] [arcmin] [kpc] [mJy] [M][mag] (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) NGC 145 ARP 19 00:31:45.7 −05:09:10 55.0 (P) 1.8 × 1.3 28.8 6156 9.97 –20.9 SB(s)dm NGC 178 IC 39, 00:39:08.5 −14:10:17 19.3 (P) 2.0 × 1.0 11.2 2586 9.40 –18.8 SB(s)m NGC 959 UGC 2002 02:32:24.0 +35:29:42 10.1 (c) 2.3 × 1.4 6.8 2709 8.49 –17.8 Sdm: IC 292 IC 1887 03:10:12.9 +40:45:56 39.8 (H) 1.2 × 0.6 13.9 4617 9.50 –19.6 Sdm DDO 36 05:07:46.9 −16:17:37 27.0 (H) 2.3 × 1.4 18.1 1528 9.57 –19.0 SB(s)m UGCA 103 DDO 230 05:10:47.0 −31:35:50 12.8 (H) 3.0 × 2.5 11.2 1413 9.12 –17.5 SB(r)dm NGC 1879 UGCA 110 05:19:48.2 −32:08:34 16.3 (P) 2.5 × 1.7 11.9 1079 9.04 –18.1 SB(s)m UGC 4151 08:04:18.7 +77:49:00 30.7 (P) 1.4 × 1.3 12.5 2220 8.97 –19.4 Sdm: NGC 2537 UGC 4274 08:13:14.7 +45:59:26 5.9 (f) 1.7 × 1.5 2.9 4810 8.23 –16.8 SB(s)m pec NGC 2730 UGC 4743 09:02:15.9 +16:50:18 51.3 (P) 1.7 × 1.3 25.4 1996 9.67 –20.3 SBdm: NGC 3057 UGC 5404 10:05:39.1 +80:17:08 20.4 (H) 2.2 × 1.3 13.1 1397 9.06 –18.3 SB(s)dm NGC 3246 UGC 5661 10:26:41.8 +03:51:43 28.6 (H) 2.4 × 1.3 20.0 1574 9.67 –19.5 SABdm NGC 3445 UGC 6021 10:54:35.9 +56:59:24 27.3 (P) 1.6 × 1.5 12.7 2960 9.50 –19.3 SAB(s)m NGC 3659 UGC 6405 11:23:45.4 +17:49:06 17.4 (P) 2.1 × 1.1 10.6 4073 9.28 –18.7 SB(s)m? NGC 3664 UGC 6419 11:24:25.0 +03:19:34 18.4 (P) 2.0 × 1.9 10.7 1962 9.27 –18.4 SB(s)m pec NGC 3839 UGC 6700 11:43:54.3 +10:47:06 78.9 (H) 1.0 × 0.5 23.0 7169 10.24 –20.4 Sdm: NGC 3879 UGC 6752 11:46:49.8 +69:22:59 19.2 (H) 2.6 × 0.5 14.5 1030 9.24 –18.7 Sdm: NGC 3991 UGC 6933 11:57:30.4 +32:20:03 42.8 (P) 0.6 × 0.27.5<11 150 10.00 –19.9 Sm NGC 4234 UGC 7309 12:17:09.2 +03:40:59 20.0 (V) 1.3 × 1.3 7.6 4068 8.50 –18.2 (R’)SB(s)m NGC 4299 UGC 7414 12:21:40.9 +11:30:03 20.0 (V) 1.7 × 1.69.9 <8086 9.20 –18.8 SAB(s)dm: NGC 4523 UGC 7713 12:33:48.0 +15:10:05 20.0 (V) 2.0 × 1.9 11.6 1303 9.26 –17.5 SAB(s)m IC 3521 UGC 7736 12:34:39.5 +07:09:36 20.0 (V) 1.3 × 0.9 7.6 2301 8.13 –17.6 SBm pec NGC 4625 IC 3675 12:41:52.6 +41:16:26 8.3 (P) 2.2 × 1.9 5.3 3575 8.71 –16.7 SAB(rs)m pec NGC 5238 UGC 8565 13:34:42.7 +51:36:51 5.2 (d) 1.7 × 1.4 2.6 1213 7.64 –14.8 SAB(s)dm DDO 180 13:38:10.3 −09:48:05 17.3 (P) 2.3 × 1.9 11.6 2075 9.14 –18.6 SB(s)m NGC 5433 UGC 8954 14:02:36.0 +32:30:38 57.5 (H) 1.6 × 0.4 26.8 11 110 9.79 –20.4 Sdm: NGC 5486 UGC 9036 14:07:25.2 +55:06:11 18.2 (P) 1.9 × 1.2 10.1 1138 9.08 –17.7 SA(s)m: NGC 5630 UGC 9270 14:27:36.7 +41:15:27 35.6 (H) 2.2 × 0.7 22.8 3536 9.68 –19.8 Sdm: NGC 6570 UGC 11137 18:11:07.3 +14:05:35 30.7 (H) 1.8 × 1.1 16.1 6250 9.44 –20.1 SB(rs)m: NGC 7162A 22:00:35.7 −43:08:30 30.3 (H) 2.6 × 2.3 22.9 1122 9.64 –19.1 SB(s)m UGC 12082 DDO 213 22:34:10.9 +32:51:44 10.8 (H) 2.6 × 2.2 8.2 1911 8.94 –16.3 Sm Notes: (a): Clemens et al. (1999), (b): Heydari-Malayeri et al. (1990), (c): Ho et al. (1997), (d): Makarova & Karachentsev (1998), (e): Meurer et al.