FIGGS: Faint Irregular Galaxies GMRT Survey – overview, observations and first results

Monthly Notices of the Royal Astronomical Society, May 2008

The Faint Irregular Galaxies GMRT Survey (FIGGS) is a Giant Metrewave Radio Telescope (GMRT) based H i imaging survey of a systematically selected sample of extremely faint nearby dwarf irregular galaxies. The primary goal of FIGGS is to provide a comprehensive and statistically robust characterization of the neutral interstellar medium properties of faint, gas-rich dwarf galaxies. The FIGGS galaxies represent the extremely low mass end of the dwarf irregular galaxies population, with a median MB∼−13.0 and median H i mass of ∼3 × 107M⊙, extending the baseline in mass and luminosity space for a comparative study of galaxy properties. The H i data are supplemented with observations at other wavelengths. In addition, distances accurate to ∼10 per cent are available for most of the sample galaxies. This paper gives an introduction to FIGGS, describes the GMRT observations and presents the first results from the H i observations. From the FIGGS data, we confirm the trend of increasing H i to optical diameter ratio with decreasing optical luminosity; the median ratio of DH i/DHo for the FIGGS sample is 2.4. Further, on comparing our data with aperture synthesis surveys of bright spirals, we find at best marginal evidence for a decrease in average surface density with decreasing H i mass. To a good approximation, the discs of gas-rich galaxies, ranging over three orders of magnitude in H i mass, can be described as being drawn from a family with fixed H i average surface density.

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FIGGS: Faint Irregular Galaxies GMRT Survey – overview, observations and first results

Ayesha Begum 2 S. S. Kaisin 0 Jayaram N. Chengalur 1 I. D. Karachentsev 0 M. E. Sharina 0 0 Special Astrophysical Observatory , Nizhnii Arkhys 369167 , Russia 1 National Centre for Radio Astrophysics , Post Bag 3, Ganeshkhind, Pune 411 007 , India 2 Institute of Astronomy, University of Cambridge , Madingley Road, Cambridge CB3 0HA A B S T R A C T The Faint Irregular Galaxies GMRT Survey (FIGGS) is a Giant Metrewave Radio Telescope (GMRT) based H I imaging survey of a systematically selected sample of extremely faint nearby dwarf irregular galaxies. The primary goal of FIGGS is to provide a comprehensive and statistically robust characterization of the neutral interstellar medium properties of faint, gas-rich dwarf galaxies. The FIGGS galaxies represent the extremely low mass end of the dwarf irregular galaxies population, with a median MB 13.0 and median H I mass of 3 107 M , extending the baseline in mass and luminosity space for a comparative study of galaxy properties. The H I data are supplemented with observations at other wavelengths. In addition, distances accurate to 10 per cent are available for most of the sample galaxies. This paper gives an introduction to FIGGS, describes the GMRT observations and presents the first results from the H I observations. From the FIGGS data, we confirm the trend of increasing H I to optical diameter ratio with decreasing optical luminosity; the median ratio of DH I/DHo for the FIGGS sample is 2.4. Further, on comparing our data with aperture synthesis surveys of bright spirals, we find at best marginal evidence for a decrease in average surface density with decreasing H I mass. To a good approximation, the discs of gas-rich galaxies, ranging over three orders of magnitude in H I mass, can be described as being drawn from a family with fixed H I average surface density. 1 I N T R O D U C T I O N 00 36 38.00 00 42 32.30 00 43 03.80 00 49 49.30 01 07 22.30 01 34 51.60 01 44 42.70 02 24 35.00 02 27 27.00 04 25 15.60 04 32 00.30 04 53 06.90 05 59 41.20 06 37 56.60 07 00 29.30 07 13 51.80 07 28 17.20 07 42 31.20 07 57 01.80 08 32 56.00 08 34 06.50 08 52 50.70 09 42 59.80 09 45 04.20 10 07 19.70 10 21 25.20 11 05 35.00 11 28 00.60 11 33 29.10 11 36 06.40 11 47 11.20 11 50 53.00 11 54 43.00 12 13 22.70 12 13 49.60 12 14 07.40 12 15 46.70 12 16 28.60 12 25 17.90 12 25 27.90 12 27 41.80 12 28 39.00 12 56 04.00 12 58 40.40 13 08 03.60 13 13 22.80 13 21 08.20 13 24 36.00 13 30 44.40 13 36 30.80 13 39 19.40 13 39 53.80 13 40 18.10 13 50 51.10 13 54 48.70 14 07 10.70 14 15 56.50 14 28 03.70 16 13 47.60 20 03 57.40 32 34 28 +40 34 19 22 15 01 21 00 58 +16 41 02 +52 5 30 +27 17 16 +56 0 42 +57 29 16 +72 48 21 +63 36 50 +67 05 57 +73 25 39 25 59 59 04 12 30 +10 31 19 +40 46 13 +16 33 40 +14 23 27 +71 01 46 +66 10 45 +33 47 52 +33 15 52 +32 14 18 +10 21 44 +71 06 58 01 51 49 +78 59 29 +49 14 17 +45 17 7 +43 40 19 +38 52 50 33 33 29 +29 55 18 38 13 53 +66 05 32 +52 23 15 +52 13 38 +26 42 53 +28 28 57 +43 29 38 +35 43 05 +03 48 41 +14 13 03 +46 49 41 +46 19 11 31 31 45 30 58 20 +54 54 36 29 14 11 +24 46 33 +40 44 21 28 53 40 +38 01 16 +35 50 15 +35 03 37 +23 03 19 46 18 06 +54 22 16 31 40 54 8.39 12.23 14.17 12.5 14.31 12.42 12.13 13.35 13.03 14.06 15.65 11.85 12.30 14.46 12.6 14.90 14.75 14.29 14.27 11.49 13.37 12.76 12.98 13.15 15.08 11.83 13.14 14.03 13.71 13.13 9.73 13.52 12.31 15.30 12.70 14.06 13.25 12.27 15.55 12.59 14.16 13.53 15.49 12.11 12.26 12.70 11.76 11.96 12.98 13.3 13.68 13.03 13.90 13.17 12.42 9.55 12.51 11.83 9.96 13.69 B V (mag) Distance (Mpc) D estimate 13, 17 Table 1 continued. 20 30 15.30 20 30 32.60 20 46 53.00 23 26 27.50 23 45 34.00 +60 26 25 +60 21 13 12 50 57 32 23 26 +38 43 4 14.54 13.72 11.09 12.94 10.78 B V (mag) Distance (Mpc) 5.6 5.6 D estimate telescopes on La Palma and 6-m Russian BTA telescope, respectively. This paper is organized as follows. In Section 2, we describe the design and the properties of the galaxy sample. The main science drivers for FIGGS are described in Section 3. The GMRT observations are described in Section 4 and the results of the survey are presented and discussed in Section 5. 2 F I G G S : S A M P L E D E F I N I T I O N A N D P R O P E R T I E S (i) absolute blue magnitude, MB > 14.5; (ii) H I flux integral >1 Jy kms1; and (iii) optical B-band major-axis >1.0 arcmin. 3 S C I E N C E D R I V E R S F O R F I G G S DDO 226 DDO 6 UGC 685 KKH 6 KK 14 KKH 11 KKH 12 UGCA 92 KK 41 KKH 34 E490-17 UGC 3755 DDO 43 KK 65 UGC 4115 KK 69 UGC 5186 UGC 5209 UGC 5456 HS 117 UGC 6145 UGC 6456 UGC 6541 KK 109 DDO 99 E379-07 KK 127 E321-014 UGC 7242 UGC 7505 KK 144 DDO 125 UGC 7605 UGC 8055 UGC 8215 DDO 167 KK 195 KK 200 UGC 8508 E444-78 UGC 8638 DDO 181 I4316 DDO 183 UGC 8833 DDO 187 P51659 KK 246 KKH 98 2004 July 8 2004 February 1 2004 June 18 2004 July 9 2004 June 19 2004 November 25 2004 July 16 2005 June 6 2004 July 8 2004 June 9 2004 June 17 2004 January 11 2005 January 16 2004 November 25 2004 July 10 2005 January 3 2004 November 26 2005 January 15 2004 July 9 2005 August 8 2005 February 11 2004 June 19 2004 November 29 2005 June 6 2005 June 30 2005 January 19 2004 July 9 2005 October 7 2004 February 3 2004 November 28 2004 July 12 2005 June 6 2004 February 1 2005 June 13 2004 November 29 2004 July 10 2005 January 4 2004 November 26 2004 January 31 2004 June 20 2004 July 9 2005 June 6 2005 August 7 2004 January 31 2004 June 16 2004 June 16 2005 January 14 2004 June 16 2004 July 10 257469 189401 51263 45166 317529 205415 36176 2057 15260 5216 404616 209421 248460 173385 235447 357569 445657 432644 438650 14369 634846 2083 144356 106318 136348 534746 46.0258 507719 37174 210422 377589 89301 204416 512724 112324 57269 460672 381593 44167 475686 168380 96308 474686 86298 121333 47259 285497 255469 24332 Synthesized beam (arcsec2) 52 46, 26 21, 19 17 50 45, 26 21, 16 12 42 40, 36 25, 27 19 41 33, 30 20, 16 11 41 38, 28 24, 16 13 46 36, 21 14, 13 10 47 37, 32 26, 16 11 42 40, 26 21, 16 14 53 52, 31 22, 20 16 53 50, 34 27, 22 18 49 46, 35 25, 24 14 42 40, 28 25, 18 16 46 42, 32 21, 15 12 41 37, 27 25, 19 17 42 41, 34 26, 18 14 56 51, 42 35, 28 24 41 37, 27 24, 15 13 41 37, 27 24, 18 15 41 36, 34 25, 22 20 46 42 42 37, 34 27, 20 14 53 39, 23 20, 16 15 42 33, 28 23, 21 15 49 41, 27 21, 18 13 45 37, 28 23, 19 16 54 47, 33 24, 19 18 49 44 51 45, 28 18, 15 10 45 37, 27 23, 18 15 45 39, 28 27, 24 18 41 40, 28 24, 19 14 45 36, 31 22, 20 14 43 38, 29 24, 16 12 40 37, 27 25, 19 17 46 39, 28 22, 17 14 51 38, 29 23, 19 16 62 54, 30 24, 18 16 48 47, 32 23, 21 17 42 38, 32 24, 18 15 48 47, 26 21, 18 11 44 36, 25 17, 16 11 50 41, 26 21, 17 14 48 46, 26 20, 15 11 42 38, 31 24, 17 13 41 39, 30 25, 21 18 46 37, 30 25, 19 13 48 41, 26 20, 15 14 61 39, 36 21, 15 11 42 41, 32 28, 15 14 Noise (mJy) 3.2, 2.4, 2.1 3.4, 1.7, 1.4 4.0, 3.5, 3.1 3.0, 2.6, 2.2 3.0, 2.5, 2.1 3.0, 2.1, 1.8 1.6, 1.3, 1.0 5.5, 4.2, 3.5 1.9, 1.3, 1.1 4.0, 2.8, 2.4 6.0, 5.8, 4.0 3.8, 3.0, 2.6 3.2, 2.6, 2.2 3.0, 2.3, 1.9 3.4, 3.2, 2.7 4.0, 3.0, 2.5 3.0, 2.2, 1.6 3.2, 2.6, 2.1 4.0, 3.2, 2.6 3.8 2.4, 2.0, 1.8 5.0, 3.4, 3.0 3.8, 3.0, 2.4 4.8, 3.5, 2.7 3.8, 3.0, 2.7 3.0, 2.0, 1.7 3.0 3.9, 2.7, 2.3 2.2, 1.9, 1.6 4.0, 3.2, 2.8 4.0, 3.2, 2.7 4.2, 3.8, 3.0 2.3, 2.0, 1.7 3.3, 2.7, 2.4 3.6, 2.7, 2.4 6.0, 4.7, 4.1 3.9, 2.7, 2.1 2.9, 2.1, 1.8 2.6, 2.2, 1.8 6.0, 4.0, 3.5 4.0, 2.6, 2.0 5.2, 3.4, 2.7 3.6, 2.8, 2.3 2.7, 2.0, 1.7 3.7, 2.8, 2.3 5.0, 4.1, 3.4 3.4, 2.6, 2.2 4.2, 3.5, 2.9 3.2, 2.7, 2.4 0025260 0116208 0204+152 0136+473 3C48 0110+565 0110+565 0410+769 0410+769 0410+769 0608-223 0745+101 0713+438 0738+177 0745+101 0741+312 0958+324 0958+324 1008+075 1035+564 1150-003 1435+760 1035+564 1227+365 1227+365 1154-350 1227+365 1154-350 1313+675 1227+365 1221+282 1227+365 1227+365 1254+116 1227+365 1227+365 1018-317 1316-336 1400+621 1316-336 1330+251 3C286 1316-336 1331+305 3C286 3C286 1316-336 1923-210 0029+349 1.5, 0.9 1.3, 0.8 1.9, 1.0 1.3, 0.8 1.6, 0.8 1.9, 0.9 1.6, 0.8 2.9, 1.8 1.3, 0.8 1.7, 0.9 2.4, 1.2 1.9, 1.0 1.6, 1.0 1.7, 0.9 1.8, 1.1 1.9, 1.3 1.5, 0.8 1.6, 0.9 1.9, 1.2 1.8, 1.1 1.4, 1.0 2.0, 1.2 2.2, 1.0 2.3, 1.2 2.0, 1.1 1.8, 1.1 1.7, 1.1 1.8, 0.9 1.4, 0.8 1.6, 1.1 1.8, 1.0 1.8, 1.2 1.5, 0.9 2.0, 1.2 2.1, 1.2 2.5, 1.3 2.2, 1.1 1.8, 0.9 1.5, 0.8 2.3, 1.6 1.7, 1.0 2.1, 1.2 1.9, 1.0 1.5, 0.9 2.0, 1.5 2.4, 1.5 1.9, 1.1 2.2, 1.2 2.1, 1.2 Date of observations Velocity coverage (km s1) Phase calibrator Continuum noise (mJy) 3.2 Dark and visible matter in small galaxies -20 Kilo Wa0vlngth20 IMAGR. Figure 5 continued Figure 5 continued 5 R E S U LT S A N D D I S C U S S I O N FIGMRT (Jy km s1) 19.5 2.0 4.8 0.5 2.6 0.3 11.8 1.2 3.0 0.3 1.8 0.2 25.0 2.5 5.5 0.6 18.8 1.9 70.0 7.1 4.6 0.4 2.1 0.2 7.3 0.7 6.5 0.7 14.2 1.4 2.52 0.3 21.6 2.2 3.8 0.4 21.5 2.2 3.0 0.3 1.4 0.1 2.0 0.2 8.0 0.8 2.1 0.2 10.1 1.0 2.7 0.3 74.7 7.5 0.76 0.08 33.0 3.3 5.0 0.5 1.3 0.1 7.2 0.7 4.7 0.5 5.2 0.5 11.5 1.2 8.7 0.9 21.7 2.2 4.93 0.5 11.0 1.1 9.0 0.9 4.5 0.5 3.7 0.4 4.8 0.5 1.6 0.2 18.3 1.8 2.3 0.2 3.5 0.4 12.2 1.2 2.2 0.2 10.5 1.1 6.3 0.6 2.2 0.2 11.1 1.1 17.4 1.7 4.4 0.4 16.4 1.6 10.6 1.0 12.1 1.2 4.4 0.4 0.87 0.11 0.79 0.10 0.77 0.10 0.99 0.11 0.72 0.89 0.10 1.09 0.12 0.34 0.42 0.70 1.02 0.11 0.89 0.1 1.11 0.13 0.96 0.11 1.20 0.15 0.97 0.11 1.00 0.11 0.85 0.11 1.01 0.11 1.07 0.12 0.96 0.11 1.21 0.13 1.16 0.14 1.00 0.11 0.72 0.90 0.10 1.08 0.12 1.04 0.12 0.93 0.10 0.46 0.05 1.02 0.11 0.91 0.10 1.06 0.11 0.92 0.10 1.01 0.11 1.00 0.11 0.87 0.10 1.34 0.32 1.03 0.11 1.05 0.11 0.88 0.10 0.91 0.11 0.94 0.11 1.21 0.14 0.83 0.12 0.90 0.10 1.07 0.12 1.05 0.12 1.07 0.12 1.05 0.11 0.86 0.11 0.93 0.10 1.03 0.11 0.53 0.82 0.11 0.73 0.11 1.05 0.11 1.07 0.12 M H I /LB DH I/DHo FIGMRT/FISD Figure 6 continued Figure 6 continued makes it one of the darkest irregular galaxies known (Begum et al. 2005a, 2008). Fig. 9 shows a tight correlation between H I mass and the H I diameter, measured at NH I of 1 1019 cm2 for the FIGGS sample. The galaxies in FIGGS sample with accurate distances are shown as the solid points, whereas the remaining galaxies are shown as the open circles. The best fit to the whole FIGGS sample shown as a solid line gives = (1.31 0.18) log + (0.43 0.08). (2) AC K N OW L E D G M E N T S R E F E R E N C E S


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Ayesha Begum, Jayaram N. Chengalur, I. D. Karachentsev, M. E. Sharina, S. S. Kaisin. FIGGS: Faint Irregular Galaxies GMRT Survey – overview, observations and first results, Monthly Notices of the Royal Astronomical Society, 2008, 1667-1682, DOI: 10.1111/j.1365-2966.2008.13150.x