MNRAS 000, 000{000 (2016) Preprint 5 October 2017 Compiled using MNRAS LATEX style file v3.0 H i debris in the IC 1459 galaxy group? Juliana Saponara,1;2y B¨arbel S. Koribalski,3 Paula Benaglia,1;2 and Manuel Fern´andez L´opez1 1Instituto Argentino de Radioastronom´ıa, (CONICET; CICPBA), C.C. No. 5, 1894,Villa Elisa, Argentina 2Facultad de Ciencias Astron´omicas y Geof´ısicas, Universidad Nacional de La Plata, Paseo del Bosque s/n, 1900 La Plata, Argentina 3CSIRO Astronomy & Space Science, Australia Telescope National Facility, P.O. Box 76, Epping, NSW 1710, Australia Received date; accepted date ABSTRACT We present H i synthesis imaging of the giant elliptical galaxy IC 1459 and its surround- ings with the Australia Telescope Compact Array (ATCA). Our search for extended H i emission revealed a large complex of H i clouds near IC 1459, likely the debris from 9 tidal interactions with neighbouring galaxies. The total H i mass (∼ 10 M ) in the detected clouds spans 250 kpc from the north-east of the gas-rich spiral NGC 7418A to the south-east of IC 1459. The extent and mass of the H i debris, which shows rather irregular morphology and kinematics, are similar to those in other nearby groups. Together with H i clouds recently detected near two other IC 1459 group members, namely IC 5270 and NGC 7418, using Phased-Array Feeds (PAFs) on the Australian Square Kilometer Array Pathfinder (ASKAP), the detected debris make up a signifi- cant fraction of the group's intergalactic medium. Key words: galaxies: groups: individual: IC 1459 | galaxies: interactions | radio lines: galaxies 1 INTRODUCTION (Serra et al. 2012). While most of the detections consist of H i discs or rings, H i debris in form of filaments and clouds Gravitational interactions between galaxies and their envi- are typical in rich groups. ronment play an important and on-going role in galaxy evo- lution, affecting their local and global properties such as gas The high density of galaxies in clusters together with content, kinematics and star formation rate. Physical pro- their high velocity dispersion typically lead to significant cesses like gas accretion, tidal effects and ram pressure strip- gas stripping, particularly from the outer discs of gas-rich ping shape the outskirts of galaxy discs, most noticeably spirals, resulting in mainly H i-deficient galaxies near the their H i extent and morphology (Westmeier et al. 2011). cluster centre (Chung et al. 2007, 2009). The observed H i Furthermore, the kinematics of the H i gas associated with filaments in, for example, Virgo and Ursa Major (Oosterloo galaxies and/or tidal debris can highlight the past orbits of & van Gorkom 2005; Boselli & Gavazzi 2006; Verheijen & their interactions. Though galaxy transformations can hap- Zwaan 2001; Wolfinger et al. 2013) hint at the disruptive pen in lower density environments (Cappellari et al. 2011), processes under way, while providing fuel for the formation arXiv:1710.01399v1 [astro-ph.GA] 3 Oct 2017 they occur more often in dense groups and clusters. Sub- of new dwarf galaxies from the tidal debris (Duc et al. 2004; stantial H i debris are typically detected near massive, often Lee-Waddell et al. 2016). early-type galaxies (Schneider 1989; Ryder et al. 2001; Bekki The galaxy group environment is less dense, and inter- et al. 2005a,b; Chung et al. 2009; English et al. 2010; Struve actions occur at much lower speeds than in clusters, allowing et al. 2010). In particular, we highlight the ATLAS-3D H i re- us to study tidal interactions, ram pressure stripping, minor sults for a large sample of nearby early-type galaxies, which mergers and gas accretion. Many detailed H i studies, rang- show a 40% H i detection rate for the non-cluster targets ing from galaxies in close pairs (e.g., Gordon et al. 2001; Ko- ribalski & Dickey 2004; Koribalski & L´opez-S´anchez 2009; Sengupta et al. 2015), compact groups (Gordon et al. 2003; ? The radio data presented here were obtained with the Aus- Koribalski et al. 2003; Serra et al. 2012), Hickson compact tralia Telescope Compact Array (ATCA) -through the Australia Telescope Online Archive- and the 64-m Parkes telescope, which groups (Hickson 1982; Verdes-Montenegro et al. 2001), loose are funded by the Commonwealth of Australia for operation as a groups (Kilborn et al. 2009; Pisano et al. 2011) and clusters National Facility managed by CSIRO. (Chung et al. 2009) have been carried out. The stripped y E-mail: [email protected] gas may be found as tidal tails, filaments, and plumes near © 2016 The Authors 2 J. Saponara et al. Table 1. Optical properties of IC 1459 group members in the observed area. Galaxy name type centre position vopt mB DB25 i P A offset from IC 1459 α; δ(J2000) [km s−1] [mag] [arcmin] [deg] [deg] [arcmin] IC 5269B SBcd 22:56:36.5, {36:14:57 1659 13.2 4.1 78 96 14.5 IC 5269A SBm 22:55:55.7, {36:20:52 2870 13.9 1.3 41 35 16.5 IC 1459 E3 22:57:11.5, {36:27:44 1691 11.0 4.9 42 47 | dE1 dE0/Im 22:57:07.6, {36:37:15 | 15.5 0.04 | | 9.5 dE2 dE0,N 22:57:10.6, {36:40:09 1838 17.3 0.32 | | 12.4 IC 5264 Sab 22:56:52.6, {36:33:15 2043 13.7 2.5 77 82 6.5 NGC 7418A SAd 22:56:41.8, {36:46:21 2102 13.8 1.8 56 83 19.5 h;m;s ◦ 0 00 Notes: Cols. (2{8) give the galaxy type, its centre position [ , ], centre velocity (vopt), blue magnitude (mB), diameter (DB25) measured at the 25th blue magnitude and the corresponding disc inclination (i) and position angle (PA). | References: ESO LV Lauberts & Valentijn(1989), de Vaucouleurs et al.(1991), da Costa et al.(1991), and Vader & Chaboyer(1994). Table 2. ATCA H i observations of the IC 1459 galaxy group. ATCA configuration H214 375 750A 6A Project C1154 C530 C1027 C689 Date 04-03-05 19-09-96 08-01-02 03-02-98 23-09-97 08-02-98 09-02-98 Time on-source [min.] 87 396 554.3 163.5 651 40 80 Primary calibrator PKS 1934{638 (14.95 Jy) Phase calibrator 0008{421 0008{421 2259{375 2259{375 Centre frequency [MHz] 1412 1412 1413 1413 Bandwidth [MHz] 8 16 8 8 No. of channels 512 512 1024 512 Channel width [km s−1] 3.3 6.6 1.6 3.3 Velocity resolution [km s−1] 4 8 2 4 Table 3. HIPASS properties of IC 1459 group members in the observed area. Galaxy name HIPASS name vsys w50 w20 FHI Reference offset from [km s−1] [km s−1] [km s−1] [Jy km s−1] optical position IC 5269B HIPASS J2256{36b 1667 ± 4 226 242 21:5 ± 3:3 (1) 1:05 IC 1459 debris HIPASS J2257{36∗ 1802 ± 12 80 111 3.0 (2) 3:05 IC 5269A HIPASS J2255{36 2872 ± 8 124 147 6.0 (2) 1:03 IC 5264 | ∼1950 ∼300 here NGC 7418A HIPASS J2256{36a 2115 ± 5 173 209 23:5 ± 3:3 (1) 1:00 Notes: Cols. (3{6) give the H i systemic velocity (vsys), 50% and 20% velocity width (w50, w20) and integrated H i flux density (FHI). | ∗ HIPASS J2257{36 encompasses some of the H i debris detected near IC 1459. | References: (1) Koribalski et al.(2004) (HIPASS BGC); (2) Meyer et al.(2004) (HICAT). the interacting galaxies, e.g. in the Abell 1367 cluster (Scott rounded by at least 15 neighbours (Walsh et al. 1990; Kil- et al. 2010) and nearby groups (e.g., Higdon 1996; Koribalski born et al. 2009). This group was recently observed by Serra et al. 2003; Koribalski & Dickey 2004; English et al. 2010). et al.(2015) using the first six PAF-equipped antennas of These extended H i structures can be difficult to detect, re- the Australian Square Kilometre Array Pathfinder1 (Hotan quiring high sensitivity single-dish observations to measure et al. 2014, ASKAP). The wide-field ASKAP H i data, ini- the low-surface brightness emission and long interferometric tially obtained with nine ∼1 deg PAF beams, resulted in observations with emphasis on short baselines such as not the detection of 11 galaxies and three H i clouds, two in the to resolve out the diffuse H i emission. The IC 1459 loose galaxy group provides a particularly 1 The wide field-of-view (30 sq degrees) delivered by the ASKAP interesting environment to study the displacement of neu- Phased-Array Feeds (PAFs) with all 36 beams is particularly suit- tral hydrogen (H i) due to tidal interactions and ram pres- able to study the H i emission in nearby galaxy groups and clus- sure stripping, since IC 1459 is a giant elliptical galaxy sur- ters. MNRAS 000, 000{000 (2016) HI debris in the IC 1459 galaxy group 3 7 proximity of the edge-on spiral galaxy IC 5270 and one close et al.(2001). They give a molecular mass limit of 2×10 M to the spiral galaxy NGC 7418 (Serra et al. 2015). Here we and suggest the emission originates from a giant molecular explore the area around IC 1459 using single-beam Australia association, possibly a merger residual. Telescope Compact Array (ATCA) archival H i data. The IC 1459 galaxy itself has a number of peculiar features, hinting at disturbances due to interactions and/or merging: twisted isophotes first noticed by Williams & Schwarzschild(1979) and Franx et al.(1989), a fast 1.1 The IC 1459 galaxy group counter-rotating stellar core (Franx & Illingworth 1988), IC 1459 is an early-type galaxy located in the centre of a faint stellar shells (Malin 1985) and a large H + N[iii] loose group at an approximate distance of 29 Mpc (Blakeslee emission-line disc showing a weak spiral structure (Goud- et al.