A multiwavelength analysis of BCDGs – Sydney, June 24, 2009 Ángel R. López-Sánchez A multiwavelength analysis of Blue Compact Dwarf Galaxies Ángel R. López-Sánchez Ángel R. López-Sánchez CSIRO /Australia Telescope National Facility (ATNF, Australia) Bärbel Koribalski (CSIRO/ATNF), César Esteban (IAC), Janine van Eymeren (U. Manchester), Attila Popping (CSIRO/ATNF) & John Hibbard (NRAO) Galaxy Metabolism – Sydney – 24 June 2009 Ángel R. López-Sánchez Ángel R. López-Sánchez CSIRO /Australia Telescope National Facility (ATNF, Australia) Bärbel Koribalski (CSIRO/ATNF), César Esteban (IAC), Janine van Eymeren (U. Manchester), Attila Popping (CSIRO/ATNF) & John Hibbard (NRAO) Galaxy Metabolism – Sydney – 24 June 2009

A multiwavelength analysis of BCDGs – Sydney, June 24, 2009 Ángel R. López-Sánchez Blue Compact Dwarf Galaxies (BCDGs) Subset of low-luminosity (M B  -18) and low metallicity (~10 % solar) galaxies undergoing a strong and short-lived episode of star formation. Quickly gas consumption – unlike spirals, star formation occurs in transient, sporadic bursts. Compact, irregular morphologies Intense narrow emission lines superposed on a blue continuum (i.e. Thuan 1991). – Sometimes, Wolf-Rayet features! The starbust and a very young stellar population dominate the optical light (Cairós et al. 2001), very often masking all evidence of the underlying older stellar population, – NIR photometry is sometimes needed to separate both components (Noeske et al. 2003). However, the origin and peculiar nature of their starburts is still poorly understood. Subset of low-luminosity (M B  -18) and low metallicity (~10 % solar) galaxies undergoing a strong and short-lived episode of star formation. Quickly gas consumption – unlike spirals, star formation occurs in transient, sporadic bursts. Compact, irregular morphologies Intense narrow emission lines superposed on a blue continuum (i.e. Thuan 1991). – Sometimes, Wolf-Rayet features! The starbust and a very young stellar population dominate the optical light (Cairós et al. 2001), very often masking all evidence of the underlying older stellar population, – NIR photometry is sometimes needed to separate both components (Noeske et al. 2003). However, the origin and peculiar nature of their starburts is still poorly understood. SBS NOT, U + B + V) IC 4662 NTT, B + R + H  )

A multiwavelength analysis of BCDGs – Sydney, June 24, 2009 Ángel R. López-Sánchez Á.R. López-Sánchez PhD Thesis (2006) supervised by C. Esteban (IAC) Massive star formation in Wolf-Rayet galaxies See López-Sánchez & Esteban, 2008, paper I (A&A 491, 131) and II (2009, in rev.) and III (2009, in prep.). We completed a detailed analysis of a sample of 20 Wolf-Rayet galaxies (many of them BCDGs) combining deep optical and NIR broad band and H  imaging together with optical spectroscopy (long slit and echelle) data + UV, HI, FIR from literature. Our multiwavelength analysis revealed that the majority of studied objects (16 up to 20) shows features such as plumes, tails, TDGs, regions with very different chemical abundances inside galaxies, perturbed kinematics of the ionized gas or lack of neutral hydrogen gas, suggesting that interactions have played an important role in the triggering mechanism of the observed star-formation bursts. Our multiwavelength analysis revealed that the majority of studied objects (16 up to 20) shows features such as plumes, tails, TDGs, regions with very different chemical abundances inside galaxies, perturbed kinematics of the ionized gas or lack of neutral hydrogen gas, suggesting that interactions have played an important role in the triggering mechanism of the observed star-formation bursts.

A multiwavelength analysis of BCDGs – Sydney, June 24, 2009 Ángel R. López-Sánchez Interferometric H I observations of BCDGs H I observations of BCDGs: Single-dish HI surveys (i.e. Thuan et al. 1999; HIPASS, Koribalski et al. 2004; Huchtmeier et al. 2005; 2007) Still not many high-resolution HI studies! And giving unexpected surprises. Importance of interf. HI observations: H I morphology and estimation of neutral gas mass globally and locally (clumps), Analysis of the H I kinematics (rotation or turbulence behaviour, total mass, dark matter), Neutral hydrogen gas is the best tracer for galaxy-galaxy interactions !!! Combining H I results with other parameters (absolute luminosity, SFR, stellar and dust content, oxygen abundance...) provide powerful clues about the nature and evolution of BCDGs. H I observations of BCDGs: Single-dish HI surveys (i.e. Thuan et al. 1999; HIPASS, Koribalski et al. 2004; Huchtmeier et al. 2005; 2007) Still not many high-resolution HI studies! And giving unexpected surprises. Importance of interf. HI observations: H I morphology and estimation of neutral gas mass globally and locally (clumps), Analysis of the H I kinematics (rotation or turbulence behaviour, total mass, dark matter), Neutral hydrogen gas is the best tracer for galaxy-galaxy interactions !!! Combining H I results with other parameters (absolute luminosity, SFR, stellar and dust content, oxygen abundance...) provide powerful clues about the nature and evolution of BCDGs. II Zw 40 - B + HI contours van Zee et al 1998 NGC 2915 – HI (blue) + B (green) + R (red) Meurer et al. 1996

A multiwavelength analysis of BCDGs – Sydney, June 24, 2009 Ángel R. López-Sánchez Observations of BCDGs using the ATCA Australia Telescope Compact Array, 6 x 22m dishes, Narrabri, NSW, Australia Deep H I line & 20 cm radio continuum observations for a sample of BCDGs – NGC 1510* – NGC 5253* Australia Telescope Compact Array, 6 x 22m dishes, Narrabri, NSW, Australia Deep H I line & 20 cm radio continuum observations for a sample of BCDGs – NGC 1510* – NGC 5253* – POX 4 – He 2-10 – POX 4 – He 2-10 – Tol 9 – Tol 30 – Tol 9 – Tol 30 – IC 4662* – IC 4870 – IC 4662* – IC 4870 – Tol – ESO 108-G017 – Tol – ESO 108-G017 Full 12h x 4 arrays: EW 367m, 750m, 1.5km, 6 km – Velocity resolution of 4 km/s – HI column density: ~ 5 x cm -2 (for 40” beam) – Angular resolution of ~20” Observations were completed on Feb 2009 * Belonging to the Local Volume HI Survey (LVHIS) project, PI B. Koribalski Full 12h x 4 arrays: EW 367m, 750m, 1.5km, 6 km – Velocity resolution of 4 km/s – HI column density: ~ 5 x cm -2 (for 40” beam) – Angular resolution of ~20” Observations were completed on Feb 2009 * Belonging to the Local Volume HI Survey (LVHIS) project, PI B. Koribalski

A multiwavelength analysis of BCDGs – Sydney, June 24, 2009 Ángel R. López-Sánchez The galaxy NGC 5253 D Hel = 4.0 Mpc (Karachentsev et al. 2004) Scale: 19 pc / arcsec Optical size: 5.0’  1.9’ Classified as Im pec, H II starburst (NED), BCDG One of the closest starbursts, observed at all wavelengths It belongs to the M83 subgroup of the Centaurus Group Deep analysis of its ionized gas using López-Sánchez et al D Hel = 4.0 Mpc (Karachentsev et al. 2004) Scale: 19 pc / arcsec Optical size: 5.0’  1.9’ Classified as Im pec, H II starburst (NED), BCDG One of the closest starbursts, observed at all wavelengths It belongs to the M83 subgroup of the Centaurus Group Deep analysis of its ionized gas using López-Sánchez et al NGC 5253 – B (blue) + V (green) + I (red) 2.5m du Pont telescope, Las Campanas Observatory, combined by Á.R. López-Sánchez 8.8’ NGC 5253 – V (blue) + I (green) + H  (red) 2.5m du Pont telescope, LCO (V, I) + 1.5m CTIO (H  ) combined by Á.R. López-Sánchez

A multiwavelength analysis of BCDGs – Sydney, June 24, 2009 Ángel R. López-Sánchez NGC 5253: Deep VLT echelle spectroscopy 4 independent regions analized in detail: Physical conditions: Ne, Te, reddening. Chemical abundances: O, N, Ne, S, Cl, Ar, Fe, He, C Kinematics of the ionized gas 169 emission lines identified in region B 2 main results: The confirmation of a localized chemical pollution, The detection of O and C recombination lines. 4 independent regions analized in detail: Physical conditions: Ne, Te, reddening. Chemical abundances: O, N, Ne, S, Cl, Ar, Fe, He, C Kinematics of the ionized gas 169 emission lines identified in region B 2 main results: The confirmation of a localized chemical pollution, The detection of O and C recombination lines. López-Sánchez, Esteban, García-Rojas, Peimbert & Rodríguez 2007, ApJ 656, 168 and López-Sánchez PhD Thesis López-Sánchez, Esteban, García-Rojas, Peimbert & Rodríguez 2007, ApJ 656, 168 and López-Sánchez PhD Thesis NGC 5253 – HST UV (blue) + H  (green) + [S II] (red) Combined by Á.R. López-Sánchez 12+log O/H = 8.28 log N/O = – log O/H = 8.18 log N/O = – 0.91

A multiwavelength analysis of BCDGs – Sydney, June 24, 2009 Ángel R. López-Sánchez New radio data of NGC 5253 from the LVHIS (Local Volume HI Survey) project using four different ATCA arrays Properties: H I flux: 31.1  1.5 Jy km/s H I mass: (8.0  0.4)  10 7 M  Dynamical mass: ~10 8 M  López-Sánchez, Koribalski & Esteban 2007 New radio data of NGC 5253 from the LVHIS (Local Volume HI Survey) project using four different ATCA arrays Properties: H I flux: 31.1  1.5 Jy km/s H I mass: (8.0  0.4)  10 7 M  Dynamical mass: ~10 8 M  López-Sánchez, Koribalski & Esteban 2007 NGC 5253: H I radio data NGC 5253 – H I map (blue) + R (green) + H  (red)

A multiwavelength analysis of BCDGs – Sydney, June 24, 2009 Ángel R. López-Sánchez NGC 5253: H I radio data ESO 154-G023 ATCA H I velocity field H I velocity field: Rotating about the optical MAJOR axis? Any kind of outflow? Formation of a polar ring? Interaction with M83 ~1 Gyr ago? Disruption/accretion of a gas-rich companion Kinematics of the ionized gas decopled from kinematics of stars? H I velocity field: Rotating about the optical MAJOR axis? Any kind of outflow? Formation of a polar ring? Interaction with M83 ~1 Gyr ago? Disruption/accretion of a gas-rich companion Kinematics of the ionized gas decopled from kinematics of stars? H I velocity field: Rotating about the optical MAJOR axis? H I velocity field: Rotating about the optical MAJOR axis?   López-Sánchez, Koribalski & Esteban 2007 and Kobulnicky & Skillman 2008 NGC 5253 ATCA H I velocity field

A multiwavelength analysis of BCDGs – Sydney, June 24, 2009 Ángel R. López-Sánchez Klemola 13 group (HIPASS J ) Located at 43.3 Mpc Tol 9 (ESO ) is a starburt WR galaxy ESO is a spiral at 20 kpc from Tol 9. Several objects surrounding Tol 9. 2 slit positions using 2.5m INT & 2.56m NOT. Chemical abundances using direct method: – 12+log O/H = 8.57±0.10 – log N/O = – 0.81 ± 0.11 Klemola 13 group (HIPASS J ) Located at 43.3 Mpc Tol 9 (ESO ) is a starburt WR galaxy ESO is a spiral at 20 kpc from Tol 9. Several objects surrounding Tol 9. 2 slit positions using 2.5m INT & 2.56m NOT. Chemical abundances using direct method: – 12+log O/H = 8.57±0.10 – log N/O = – 0.81 ± 0.11 WR galaxy Tol 9 within the Klemola 13 group López-Sánchez & Esteban (2008, 2009)

A multiwavelength analysis of BCDGs – Sydney, June 24, 2009 Ángel R. López-Sánchez Our new deep images reveal a bridge towards a dwarf companion object at 10 kpc. – Composed by an OLD pop. Our new deep images reveal a bridge towards a dwarf companion object at 10 kpc. – Composed by an OLD pop. WR galaxy Tol 9 within the Klemola 13 group Deep V image, 2.56m NOT López-Sánchez (2006) López-Sánchez & Esteban (2008)

A multiwavelength analysis of BCDGs – Sydney, June 24, 2009 Ángel R. López-Sánchez Our new deep images reveal a bridge towards a dwarf companion object at 10 kpc. – Composed by an OLD pop. H  image reveals on-going star formation activity and a filamentary structure. Our new deep images reveal a bridge towards a dwarf companion object at 10 kpc. – Composed by an OLD pop. H  image reveals on-going star formation activity and a filamentary structure. WR galaxy Tol 9 within the Klemola 13 group Continuum-substracted H  i mage, 2.56m NOT López-Sánchez (2006) López-Sánchez & Esteban (2008)

A multiwavelength analysis of BCDGs – Sydney, June 24, 2009 Ángel R. López-Sánchez Tol 9 and surroundings López-Sánchez & Esteban (2008)

A multiwavelength analysis of BCDGs – Sydney, June 24, 2009 Ángel R. López-Sánchez WR galaxy Tol 9 within the Klemola 13 group Tol 9 The kinematics of the ionized gas was studied via the analysis of emission line profiles of our spectra. – PA 49º: Strange velocity pattern that can not be attributed to rotation. – PA 109º: It crosses the filamentary H  structure, showing a very intriguing behaviour: a bipolar bubble expanding at about 80 km s -1 ? – PA 109º: It crosses the filamentary H  structure, showing a very intriguing behaviour: a bipolar bubble expanding at about 80 km s -1 ? PA 49º PA 109º López-Sánchez & Esteban (2009)

A multiwavelength analysis of BCDGs – Sydney, June 24, 2009 Ángel R. López-Sánchez HIPASS reveals a considerable amount of atomic gas, probably mostly associated with ESO WR galaxy Tol 9 within the Klemola 13 group We obtained ATCA H I ob- servations in 6 km, 1.5 km, 750m and 350m arrays Also cont. observations at 20, 13, 6 and 3 cm.

A multiwavelength analysis of BCDGs – Sydney, June 24, 2009 Ángel R. López-Sánchez WR galaxy Tol 9 within the Klemola 13 group H I distribution Total HI mass: – M HI : 3.1  10 9 M  Tol 9 cloud: – M HI : 2.2  10 9 M  – M HI /L B = 0.21 – M Dyn /L B = 18.8 ESO : – M HI : 8.7  10 8 M  – M HI /L B = 0.07 – M Dyn /L B = 10.4 Tail: – M HI : 6.0  10 7 M  H : – M HI : 3.5  10 7 M  H I distribution Total HI mass: – M HI : 3.1  10 9 M  Tol 9 cloud: – M HI : 2.2  10 9 M  – M HI /L B = 0.21 – M Dyn /L B = 18.8 ESO : – M HI : 8.7  10 8 M  – M HI /L B = 0.07 – M Dyn /L B = 10.4 Tail: – M HI : 6.0  10 7 M  H : – M HI : 3.5  10 7 M  78” x 32” Tail Tol 9 ESO H López-Sánchez et al. In prep.

A multiwavelength analysis of BCDGs – Sydney, June 24, 2009 Ángel R. López-Sánchez WR galaxy Tol 9 within the Klemola 13 group H I kinematics ESO : – M Dyn : 1.7  M  – M Dyn /L B = 10.4 Tol 9 cloud: – Disturbed kin. at E – M Dyn : 2.0  M  – M Dyn /L B = 18.8 Tail: - – Cte velocity H I kinematics ESO : – M Dyn : 1.7  M  – M Dyn /L B = 10.4 Tol 9 cloud: – Disturbed kin. at E – M Dyn : 2.0  M  – M Dyn /L B = 18.8 Tail: - – Cte velocity 78” x 32” Tail Tol 9 ESO H PA 273º PA 192º López-Sánchez et al. In prep.

A multiwavelength analysis of BCDGs – Sydney, June 24, 2009 Ángel R. López-Sánchez Tol 30 – B (blue) + R (green) + H  (red) 2.6m NOT WR galaxy Tol 30 Tol 30 – B (blue) + V (green) + R (red) 2.5m INTTol 30 – H I map (blue) + B (green) + R (red) D = 29.3 Mpc 1’ = 8.5 kpc Optical size: 1.2’  1’ Two intense star-forming regions in opposite places within the galaxy Optical imagery and ionized gas analysis using 2.56m NOT: – WR features – 12+log O/H = 8.07 – log N/O = – 1.5 Deep optical imagery using 2.5m INT – Detection of nearby and diffuse non-stellar objects D = 29.3 Mpc 1’ = 8.5 kpc Optical size: 1.2’  1’ Two intense star-forming regions in opposite places within the galaxy Optical imagery and ionized gas analysis using 2.56m NOT: – WR features – 12+log O/H = 8.07 – log N/O = – 1.5 Deep optical imagery using 2.5m INT – Detection of nearby and diffuse non-stellar objects López-Sánchez et al. In prep.

A multiwavelength analysis of BCDGs – Sydney, June 24, 2009 Ángel R. López-Sánchez WR galaxy Tol 30 Tol 30 – H I map (blue) + B (green) + R (red) H I distribution Total HI mass: – M HI : 1.4  10 9 M  Tol 30 MB: – M HI : 1.1  10 9 M  – M HI /L B = 1.2 – M Dyn /L B = 17.1 Northern tail: – M HI : 2.1  10 8 M  – 15% total HI mass Eastern tail: – M HI : 9.1  10 7 M  – 7% total HI mass TDG or dwarf obj?: – M HI : 2.3  10 7 M  – M HI /L B = 0.12 – It shows rotation! – M Dyn /L B = 7.3 H I distribution Total HI mass: – M HI : 1.4  10 9 M  Tol 30 MB: – M HI : 1.1  10 9 M  – M HI /L B = 1.2 – M Dyn /L B = 17.1 Northern tail: – M HI : 2.1  10 8 M  – 15% total HI mass Eastern tail: – M HI : 9.1  10 7 M  – 7% total HI mass TDG or dwarf obj?: – M HI : 2.3  10 7 M  – M HI /L B = 0.12 – It shows rotation! – M Dyn /L B = 7.3 López-Sánchez et al. In prep. Tol 30 ? Northern tail Eastern tail Tol 30 dwarf – B (blue) + R (green) + H  (red) 1 frame 150s per filter, not reduced Observations at 2.3m ANU 2 nights ago!

A multiwavelength analysis of BCDGs – Sydney, June 24, 2009 Ángel R. López-Sánchez The galaxy pair NGC 1512 / 1510 NGC 1512: – SB(r)ab, Z ~0.7 Zo – D = 9.5 Mpc – Bar ~ 3’ = 8.3 kpc – Ring ~ 3’ x 2’ = 8.3 x 5.5 kpc – Nuclear ring ~ 16” x 12” (740 x 550 pc) NGC 1510: – S0, BCD, WR, Z~0.2 Zo – Probable N enrichment – 5’ = 13.8 kpc from NGC 1512 H  images (Meurer et al. 2006) reveal many star forming regions – Sizes 2”–5” (90–230 pc) – Dozens in the ring – NGC 1510 – But also in external regions with no evident continuum emission! NGC 1512: – SB(r)ab, Z ~0.7 Zo – D = 9.5 Mpc – Bar ~ 3’ = 8.3 kpc – Ring ~ 3’ x 2’ = 8.3 x 5.5 kpc – Nuclear ring ~ 16” x 12” (740 x 550 pc) NGC 1510: – S0, BCD, WR, Z~0.2 Zo – Probable N enrichment – 5’ = 13.8 kpc from NGC 1512 H  images (Meurer et al. 2006) reveal many star forming regions – Sizes 2”–5” (90–230 pc) – Dozens in the ring – NGC 1510 – But also in external regions with no evident continuum emission! NGC 1512: – SB(r)ab, Z ~0.7 Zo – D = 9.5 Mpc – Bar ~ 3’ = 8.3 kpc – Ring ~ 3’ x 2’ = 8.3 x 5.5 kpc – Nuclear ring ~ 16” x 12” (740 x 550 pc) NGC 1512: – SB(r)ab, Z ~0.7 Zo – D = 9.5 Mpc – Bar ~ 3’ = 8.3 kpc – Ring ~ 3’ x 2’ = 8.3 x 5.5 kpc – Nuclear ring ~ 16” x 12” (740 x 550 pc)

A multiwavelength analysis of BCDGs – Sydney, June 24, 2009 Ángel R. López-Sánchez H I in NGC 1512 / 1510 ATCA observ. using 7 arrays Mosaic using 4 pointings Total int. time: 3.11 days Huge amount of neutral gas! Two extended spiral arms Two TDG candidates NGC 1512: NGC 1510: ATCA observ. using 7 arrays Mosaic using 4 pointings Total int. time: 3.11 days Huge amount of neutral gas! Two extended spiral arms Two TDG candidates NGC 1512: NGC 1510: Koribalski & López-Sánchez (2009, MNRAS) NGC 1512 NGC 1510 TDG – M HI = 5.7  10 9 M  – M Dyn ~ 4 x M  – M HI /L B = 1 – M HI ~ 4x10 7 M  – M HI /L B ~0.07 – M HI = 5.7  10 9 M  – M Dyn ~ 4 x M  – M HI /L B = 1 – M HI ~ 4x10 7 M  – M HI /L B ~0.07

A multiwavelength analysis of BCDGs – Sydney, June 24, 2009 Ángel R. López-Sánchez H I / UV comparison in NGC 1512/1510 Koribalski & López-Sánchez (2009, MNRAS, in rev.)

A multiwavelength analysis of BCDGs – Sydney, June 24, 2009 Ángel R. López-Sánchez NGC 1512 / 1510 Rotation fit and residues The velocity field is mainly rotation, But we found some discrepances in the most external regions and in the position of NGC Star formation activity and the external HI structures seem to be consequence of the interaction that NGC 1512 and NGC 1510 are experiencing. Minor merger ~ 400 Myr The velocity field is mainly rotation, But we found some discrepances in the most external regions and in the position of NGC Star formation activity and the external HI structures seem to be consequence of the interaction that NGC 1512 and NGC 1510 are experiencing. Minor merger ~ 400 Myr Koribalski & López-Sánchez 2009, MNRAS NGC 1512 / 1510 also include in the THING project, with higher spatial resolution (Deane & de Blok, in prep) Koribalski & López-Sánchez 2009, MNRAS NGC 1512 / 1510 also include in the THING project, with higher spatial resolution (Deane & de Blok, in prep)

A multiwavelength analysis of BCDGs – Sydney, June 24, 2009 Ángel R. López-Sánchez Further tidal tails features in BCDGs IC 4870 – D = 10.2 Mpc – Optical prop: 35” compact core, Elliptical low-luminosity component 1.4’x0.4’ – H I reveals two long tails 3.7’ (N) and 4.2’(S) Knot in S tail has ~14% of the neutral mass. – Merger of two independent HI clouds? ESO 108-G017 – D = 28.2 Mpc – Faint optical tail – HI is +5 times optical size! – Elongated HI cloud with some disturbed kinematics IC 4870 – D = 10.2 Mpc – Optical prop: 35” compact core, Elliptical low-luminosity component 1.4’x0.4’ – H I reveals two long tails 3.7’ (N) and 4.2’(S) Knot in S tail has ~14% of the neutral mass. – Merger of two independent HI clouds? ESO 108-G017 – D = 28.2 Mpc – Faint optical tail – HI is +5 times optical size! – Elongated HI cloud with some disturbed kinematics He 2-10: Extended HI emission perpendicular to rotation axis? POX 4: Independent HI cloud + strange HI kinematics? He 2-10: Extended HI emission perpendicular to rotation axis? POX 4: Independent HI cloud + strange HI kinematics?

A multiwavelength analysis of BCDGs – Sydney, June 24, 2009 Ángel R. López-Sánchez Conclusions Detailed multiwavelength analysis of BCDGs – Optical / NIR imagery – H  imagery – Deep optical spectroscopy (long slit and echelle) – H I and 20cm observations H I data are fundamental to understand the dynamical evolution of these objects. Despite the environment, ALL studied BCDGs show interactions features, very evident in the majority of them, confirming the main result found in our analysis of a sample of Wolf-Rayet galaxies (López-Sánchez PhD, 2006; López-Sánchez & Esteban 2008, 2009a,b) Detailed multiwavelength analysis of BCDGs – Optical / NIR imagery – H  imagery – Deep optical spectroscopy (long slit and echelle) – H I and 20cm observations H I data are fundamental to understand the dynamical evolution of these objects. Despite the environment, ALL studied BCDGs show interactions features, very evident in the majority of them, confirming the main result found in our analysis of a sample of Wolf-Rayet galaxies (López-Sánchez PhD, 2006; López-Sánchez & Esteban 2008, 2009a,b) Are interactions between dwarf objects the main triggering mechanism of starbursts, specially in BCDGs? Many surprises will come from HI surveys, i.e. using ASKAP, Australia SKA Pathfinder!! Are interactions between dwarf objects the main triggering mechanism of starbursts, specially in BCDGs? Many surprises will come from HI surveys, i.e. using ASKAP, Australia SKA Pathfinder!!