the environment of nearby blue compact dwarf galaxies

The environment of nearby BCDGs – Granada, May 12, 2009 Ángel R. López-Sánchez The environment of nearby BCDGs – Granada, May 12, 2009 Ángel R. López-Sánchez

The environment of nearby Blue Compact Dwarf GalaxiesThe environment of nearby Blue Compact Dwarf Galaxies

Ángel R. López-SánchezÁngel R. López-SánchezCSIRO /Australia Telescope National Facility (ATNF, Australia)

Bärbel Koribalski (CSIRO/ATNF), César Esteban (IAC), Bärbel Koribalski (CSIRO/ATNF), César Esteban (IAC), Janine van Eymeren (U. Manchester), Attila Popping (CSIRO/ATNF) & John Janine van Eymeren (U. Manchester), Attila Popping (CSIRO/ATNF) & John

Hibbard (NRAO)Hibbard (NRAO)

Galaxies in Isolation – Granada, Spain – 12 May 2009

Ángel R. López-SánchezÁngel R. López-SánchezCSIRO /Australia Telescope National Facility (ATNF, Australia)

Bärbel Koribalski (CSIRO/ATNF), César Esteban (IAC), Bärbel Koribalski (CSIRO/ATNF), César Esteban (IAC), Janine van Eymeren (U. Manchester), Attila Popping (CSIRO/ATNF) & John Janine van Eymeren (U. Manchester), Attila Popping (CSIRO/ATNF) & John

Hibbard (NRAO)Hibbard (NRAO)

Galaxies in Isolation – Granada, Spain – 12 May 2009


Blue Compact Dwarf Galaxies (BCDGs)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.

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)


Á.R. López-Sánchez PhD Thesis (2006) supervised by C. Esteban (IAC)

Á.R. López-Sánchez PhD Thesis (2006) supervised by C. Esteban (IAC)

Massive star formation in Wolf-Rayet galaxies

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.).

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.

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.

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.


Multiwavelength observations of BCDGsMultiwavelength observations of BCDGs

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.

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.

NGC 2915 – HI (blue) + B (green) + R (red)

II Zw 40 - B + HI contours

van Zee et al 1998

Meurer et al. 1996


Observations of BCDGs using the ATCAObservations 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 1924-416– ESO 108-G017

– Tol 1924-416– 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 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!

Full 12h x 4 arrays: 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!


BCDGs in different environmentsBCDGs in different environments

In galaxy groups:– Tol 9– Tol 30– NGC 5253

In galaxy groups:– Tol 9– Tol 30– NGC 5253

Tol 1924-416Tol 1924-416

ESO 338-004BESO 338-004B

In galaxy pairs:– Tol 1924-416

– NGC 1510

In galaxy pairs:– Tol 1924-416

– NGC 1510

Apparently isolated– IC 4662

– IC 4870

– ESO 108-G017

Apparently isolated– IC 4662

– IC 4870

– ESO 108-G017

– He 2-10

– POX 4

– He 2-10

– POX 4

Tol 9 within Klemola 13 group

Tol 9 within Klemola 13 group

Galaxy pair Tol 1924-416 & ESO 338-004B

Galaxy pair Tol 1924-416 & ESO 338-004B

IC 4870IC 4870


Klemola 13 group (HIPASS J1034-28)

Located at 43.3 Mpc

Tol 9 (ESO 436-42) is a starburt WR 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

Klemola 13 group (HIPASS J1034-28)

Located at 43.3 Mpc

Tol 9 (ESO 436-42) is a starburt WR 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

WR galaxy Tol 9 within the Klemola 13 groupWR galaxy Tol 9 within the Klemola 13 group

López-Sánchez & Esteban (2008, 2009)López-Sánchez & Esteban (2008, 2009)


Our new deep images reveal a bridge towards a dwarf companion object at 10 kpc.

– Composed by an OLD pop.




Deep V image, ALFOSC @ 2.56m NOT López-Sánchez (2006)

López-Sánchez & Esteban (2008)




H image reveals on-going star formation activity and a filamentary structure.



H image reveals on-going star formation activity and a filamentary structure.


Continuum-substracted H image, ALFOSC @ 2.56m NOT López-Sánchez (2006)

López-Sánchez & Esteban (2008)


Tol 9 and surroundingsTol 9 and surroundings

López-Sánchez & Esteban (2008)López-Sánchez & Esteban (2008)



Tol 9

The kinematics of the ionized gas was studied via the analysis of emission line profiles of our spectra.

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 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 49ºPA 109º

López-Sánchez & Esteban (2009)López-Sánchez & Esteban (2009)


HIPASS reveals a considerable amount of atomic gas, probably mostly associated with ESO 436-46.

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

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.

Also cont. observations at 20, 13, 6 and 3 cm.



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

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

78” x 32” 78” x 32”

Tail

Tol 9

ESO 436-46

H 1032-2819



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

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

78” x 32” 78” x 32”

Tail

Tol 9

ESO 436-46

H 1032-2819

PA 273º

PA 192º

The M 83 subgroup

5º

Koribalski 2006Koribalski et al. 2009 (in prep)


The galaxy NGC 5253The 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

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

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


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

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 radio dataNGC 5253: H I radio data

NGC 5253 – H I map (blue) + R (green) + H (red)


NGC 5253: H I radio dataNGC 5253: H I radio data

Optical major axis

Rotation?

NGC 5253 ATCA H I velocity field NGC 5253 ATCA H I velocity field

H I velocity field:

Rotating about the optical MAJOR axis?

H I velocity field:



NGC 5253: H I radio dataNGC 5253: H I radio data ESO 154-G023 ATCA H I velocity field

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 companionKinematics 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 companionKinematics of the ionized gas decopled from kinematics of stars?

H I velocity field:


H I velocity field:


López-Sánchez, Koribalski & Esteban 2007 and Kobulnicky & Skillman 2008López-Sánchez, Koribalski & Esteban 2007 and Kobulnicky & Skillman 2008NGC 5253 ATCA H I velocity field NGC 5253 ATCA H I velocity field


The galaxy pair NGC 1512 / 1510The 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’


(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!



(740 x 550 pc)



(740 x 550 pc)


H I in NGC 1512 / 1510H 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, in rev.)Koribalski & López-Sánchez (2009, MNRAS, in rev.)

NGC 1512NGC 1512

NGC 1510NGC 1510

TDGTDG

TDGTDG

– MHI = 5.7109 M

– MDyn~ 4 x 1011 M

– MHI/LB = 1

– MHI ~ 4x107 M

– MHI/LB ~0.07

– MHI = 5.7109 M

– MDyn~ 4 x 1011 M

– MHI/LB = 1

– MHI ~ 4x107 M

– MHI/LB ~0.07


NGC 1512 / 1510 Rotation fit and residues

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

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)

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)


Apparently isolated BCDGsApparently 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 MH I distribution has 2 parts:

inner high column density and lower column density ending in a kind of tail.

– Distorted H I velocity fieldVelocity 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.

IC 4662van 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 MH I distribution has 2 parts:

inner high column density and lower column density ending in a kind of tail.

– Distorted H I velocity fieldVelocity 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)

– Intringuing H kinematics, outflows– Chemical properties may indicate two objects! (Hidalgo-Gámez et al. 2001)


Apparently isolated BCDGsApparently 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

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?

He 2-10: Extended HI emission perpendicular to rotation axis? POX 4: Independent HI cloud + strange HI kinematics?


ConclusionsConclusions

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?

Are BCDGs real isolated systems?

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?

Are BCDGs real isolated systems?

Many surprises will come from HI surveys (i.e. using ASKAP, Australia SKA Pathfinder)

the environment of nearby blue compact dwarf galaxies

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