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The environment of nearby Blue Compact Dwarf Galaxies

The Local Volume HI Survey. The environment of nearby Blue Compact Dwarf Galaxies. Ángel R. López-Sánchez CSIRO /Australia Telescope National Facility (ATNF, Australia)

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The environment of nearby Blue Compact Dwarf Galaxies

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  1. The Local Volume HI Survey The environment of nearby Blue Compact Dwarf Galaxies 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) Galaxies in Isolation – Granada, Spain – 12 May 2009

  2. Blue Compact Dwarf Galaxies (BCDGs) • Subset of low-luminosity (MB  -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, even Wolf-Rayet features are detected! • 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, • High spatial resolution 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. II Zw 40 (ALFOSC @ NOT, B + V + R) SBS 1054+365 (ALFOSC @ NOT, U + B + V)

  3. Massive star formation in Wolf-Rayet galaxies Á.R. López-Sánchez PhD Thesis (2006) supervised by C. Esteban (IAC) 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. 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.

  4. Multiwavelength observations of BCDGs NGC 2915 – HI (blue) + B (green) + R (red) We are obtaining deep multi-wavelength data of a sample of BCDGs combining • Optical and NIR broad-band imagery, • H imagery, • Optical spectroscopy (long slit, echelle, IFU), • 21-cm radio continuum and HI observations • Single-dish HI surveys(i.e. Thuan et al. 1999; HIPASS, Koribalski et al. 2004; Huchtmeier et al. 2005; 2007), • But still not many high-resolution HI studies! And giving unexpected surprises. Importance of interferometric HI observ.: • Estimation of neutral gas mass, • 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 such as the absolute luminosity, star formation rate, stellar and dust content or oxygen abundance, provide powerful clues about the nature and evolution of BCDGs. Meurer et al. 1996 II Zw 40 - B + HI contours van Zee et al 1998

  5. Observations of BCDGs using the ATCA • POX 4 • He 2-10 • IC 4662* • IC 4870 • Tol 1924-416 • ESO 108-G017 • Tol 9 • Tol 30 • 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* • Full12h x 4arrays: EW 367m, 750m, 1.5km, 6 km • Velocity resolution of 4 km/s • HI column density: • ~ 5 x 1019 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, see TALK ON THURSDAY!

  6. Tol 1924-416 ESO 338-004B BCDGs in different environments • In galaxy pairs: • Tol 1924-416 • NGC 1510 • Apparently isolated • IC 4662 • IC 4870 • ESO 108-G017 • He 2-10 • POX 4 • In galaxy groups: • Tol 9 • Tol 30 • NGC 5253 Tol 9 within Klemola 13 group Galaxy pair Tol 1924-416 & ESO 338-004B IC 4870

  7. WR galaxy Tol 9 within the Klemola 13 group • Klemola 13 group (HIPASS J1034-28) • Located at 43.3 Mpc • Tol 9 (ESO 436-42) is a starburtWR galaxy • ESO 436-46 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 López-Sánchez & Esteban (2008, 2009)

  8. Deep V image, ALFOSC @ 2.56m NOTLópez-Sánchez (2006) López-Sánchez & Esteban (2008) WR galaxy Tol 9 within the Klemola 13 group • Our new deep images reveal a bridge towards a dwarf companion object at 10 kpc. • Composed by an OLD pop.

  9. WR galaxy Tol 9 within the Klemola 13 group • 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. Continuum-substractedH image, ALFOSC @ 2.56m NOTLópez-Sánchez (2006) López-Sánchez & Esteban (2008)

  10. Tol 9 and surroundings López-Sánchez & Esteban (2008)

  11. WR galaxy Tol 9 within the Klemola 13 group • The kinematics of the ionized gas was studied via the analysis of emission line profiles of our spectra. Tol 9 • 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 49º PA 109º López-Sánchez & Esteban (2009)

  12. WR galaxy Tol 9 within the Klemola 13 group • HIPASS reveals a considerable amount of atomic gas, probably mostly associated with ESO 436-46. • 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.

  13. 78” x 32” WR galaxy Tol 9 within the Klemola 13 group H I distribution • Total HI mass: • MHI: 3.1  109 M • Tol 9 cloud (W): • MHI: 2.2  109 M • MHI/LB = 0.21 • MDyn/LB = 18.8 • ESO 436-46: • MHI: 8.7  108 M • MHI/LB = 0.07 • MDyn/LB = 10.4 • Tail: • MHI: 6.0  107 M • H1032-2819: • MHI: 3.5  107 M Tail ESO 436-46 Tol 9 H 1032-2819

  14. 78” x 32” WR galaxy Tol 9 within the Klemola 13 group H I kinematics • ESO 436-46: • MDyn: 1.7  1011 M • MDyn/LB = 10.4 • Tol 9 cloud (W): • Disturbed kin. at E • MDyn: 2.0  1011 M • MDyn/LB = 18.8 • Tail: - – Cte velocity PA 192º Tail ESO 436-46 PA 273º Tol 9 H 1032-2819

  15. 5º The M 83 subgroup Koribalski 2006 Koribalski et al. 2009 (in prep)

  16. 8.8’ The galaxy NGC 5253 • DHel= 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 UVES@VLT López-Sánchez et al. 2007 NGC 5253 – B (blue) + V (green) + I (red) 2.5m du Pont telescope, Las Campanas Observatory, combined by Á.R. López-Sánchez 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

  17. NGC 5253: H I radio data 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)  107 M • Dynamical mass: ~108 M López-Sánchez, Koribalski & Esteban 2007 NGC 5253 – H I map (blue) + R (green) + H (red)

  18. NGC 5253: H I radio data Rotation? H I velocity field: Rotating about the optical MAJOR axis? Optical major axis NGC 5253 ATCA H I velocity field

  19. 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? •  López-Sánchez, Koribalski & Esteban 2007 and Kobulnicky & Skillman 2008 NGC 5253 ATCA H I velocity field

  20. 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 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!

  21. H I in NGC 1512 / 1510 • ATCA observ. using 7arrays • Mosaicusing 4 pointings • Total int. time:3.11 days • Huge amount of neutral gas! • Two extended spiral arms • Two TDG candidates • NGC 1512: • NGC 1510: TDG NGC 1512 NGC 1510 • MHI = 5.7109 M • MDyn~ 4 x 1011 M • MHI/LB = 1 • MHI ~ 4x107 M • MHI/LB ~0.07 TDG • Koribalski & López-Sánchez (2009, MNRAS, in rev.)

  22. 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 1510. • 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, in rev. NGC 1512 / 1510 also include in the THING project, with higher spatial resolution (Deane & de Blok, in prep)

  23. Apparently isolated BCDGs • IC 4662 van Eymeren 2008, PhD, van Eymeren+ 2009 (in prep) • BCDG included in The Local Volume HI Survey(Koribalski et al. 2009, in prep) • D = 2.44 Mpc, • Opt. size = 3.0’ x 1.6’ • H I morphology: • H I size= 15’ x 12’ • H I mass: 1.6  108 M • H I distribution has 2 parts: inner high column density and lower column density ending in a kind of tail. • Distorted H I velocity field • Velocity gradient runs from NE with 220 km s-1 to SW with 380 km s-1. • There is a change of ~90º in its center. • Intringuing H kinematics, outflows • Chemical properties may indicate two objects! (Hidalgo-Gámez et al. 2001)

  24. Apparently isolated 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 • H I is +5 times optical s.! • 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?

  25. Conclusions • Detailed multiwavelength analysis of BCDGs • Optical / NIR imagery • H imagery • Deep optical spectroscopy (long slit and echelle) • H I and 20cm observations • H Idata are fundamental to understand thedynamical evolutionof 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? • Are BCDGs real isolated systems? • Many surprises will come from HI surveys (i.e. using ASKAP,Australia SKA Pathfinder)

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