Nitrogen excess in starburst galaxies chemical enrichment via winds of wolf rayet stars
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The Local Volume HI Survey. Nitrogen excess in starburst galaxies: chemical enrichment via winds of Wolf-Rayet stars?. Ángel R. López-Sánchez César Esteban (IAC), Jorge García-Rojas (IA-UNAM), Adal Mesa Delgado (IAC) & Luis López-Martín (IAC).

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Nitrogen excess in starburst galaxies: chemical enrichment via winds of Wolf-Rayet stars?

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Nitrogen excess in starburst galaxies chemical enrichment via winds of wolf rayet stars

The Local Volume HI Survey

Nitrogen excess in starburst galaxies:chemical enrichment via winds of Wolf-Rayet stars?

Ángel R. López-Sánchez

César Esteban (IAC), Jorge García-Rojas (IA-UNAM), Adal Mesa Delgado (IAC) & Luis López-Martín (IAC)

CSIRO /Australia Telescope National Facility (ATNF, Australia)

The Cosmic Odyssey of the Elements – Aegina – Greece – 23 Jun 2008


Chemical evolution of galaxies

Chemical evolution of galaxies

  • a elements (S, Ne, Ar): const. with O/H

    • Primary production in massive stars (Izotov & Thuan 1999; Izotov et al. 2006)

  • N/O is not so evident!

Dlog (N/O) ~ 0.5

  • Constant for 12+log O/H < 7.6 Primary production

  • Dispersion for 7.6 < 12+log O/H < 8.3 Delay in N production & loss via galactic winds

  • Increases for 12+log O/H > 8.3 Secondary production

    Kobulnicky et al.1997;

    Izotov et al. 2006


Starburst galaxies with high n o

Starburst galaxies with high N/O

HS 0837+4717: Dlog (N/O) = +0.8

  • Dlog (N/O) ~ 0.5 for the typical O/H value

    • Pustilnik et al. 2004

  • Common feature: Wolf-Rayet galaxies!

    • Winds of the WR stars may produce a N enrichment

    • However, the N enrichment should be very localized and a short episode

  • Observational problem:

    • [N II] ll6548,6583 are very close to Ha.

    • + broadening effects (kinematics)

New data with enough spectral resolution and a systematic study is needed !!

  • ISIS @ 4.2m WHT : 0.36 A/pix

  • UVES @ 8.2m VLT: 0.024 A/pix

Gaussian fit for Ha and [N II] in HS 0837+4717 using long-slit spectroscopic data from 6m BTA and a spectral resolution of 2.38 A/pix (Pustilnik et al. 2004).


Wolf rayet galaxies

WN

WC

Emission lines of WR stars

Wolf-Rayet galaxies

A subset of emission-line and H II galaxies whose integrated spectra show broad emission features attributed to the presence of Wolf-Rayet stars.

Blue WR Bump ~ 4650 Å WNL stars

Blue WR Bump ~ 5800 Å WC stars

  • The number of WR stars with respect O stars is high, the burst shoud be short.

  • IMF extended to HIGH masses

  • Short-lived starburst(< 6 Myr)

  • Emission lines :

  • Recombination lines (RL) of H y He

  • Collisionally excitedlines (CEL) of O, N, S, Ne, Ar, Cl, Fe ...

Last catalogue of WR galaxies140 objects(Schaerer et al. 1999),nowadays ~250 WR galaxies known


Nitrogen excess in starburst galaxies chemical enrichment via winds of wolf rayet stars

III Zw 107

SBS 0948+532

  • NGC 1741

  • Mkn 1087

  • Haro 15

  • Mkn 1199

  • Mkn 5

  • POX 4

  • UM 420

  • III Zw 107

  • IRAS 08339+6517

  • IRAS 08208+2816

  • NGC 1741

  • Mkn 1087

  • Haro 15

  • Mkn 1199

  • Mkn 5

  • POX 4

  • UM 420

  • III Zw 107

  • IRAS 08339+6517

  • IRAS 08208+2816

  • SBS 0926+606

  • SBS 0948+532

  • SBS 1054+365

  • SBS 1211+540

  • SBS 1319+579

  • SBS 1415+437

  • Tol 9

  • Tol 1457-262

  • Arp 252

  • NGC 5253

  • SBS 0926+606

  • SBS 0948+532

  • SBS 1054+365

  • SBS 1211+540

  • SBS 1319+579

  • SBS 1415+437

  • Tol 9

  • Tol 1457-262

  • Arp 252

  • NGC 5253

SBS 1054+365

SBS 1415+437

UM 420

Mkn 5

Main aim: Study the massive star formation activity in WR galaxies and the role that interactions with dwarf objects have in the triggering mechanism of starbursts.

SBS 1211+540

SBS 0926+606

IRAS 08339+6517

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

Massive star formation in WR galaxies

We have performed a detailed analysis of a sample of 20 WR galaxies combining deep optical and NIR broad band and H imaging together with optical spectroscopy (long slit and echelle) data.

The sample:

See López-Sánchez & Esteban, 2008, paper I (in rev.) and II & III (in prep.)


Um 420

UM 420

  • Located at 237 Mpc

  • At 16.5” from UGC 1809, located at 97 Mpc

  • It has very blue colors (U-B) = -0.8

  • and a lot of Ha emission, with SFR = 3.7 Mo/yr

UGC 1809

  • Disturbed morphology and kinematics

  • New optical spectra (4.2m WHT)

UM 420

López-Sánchez, 2006, PhD

López-Sánchez & Esteban, 2008


Um 4201

UM 420

  • New optical spectra (4.2m WHT)

    • We detect both the WR bump and the He II l4686 emission line

    • Very good estimation of Te, Ne and C(Hb)

    • Excellent estimation of [N II] and Ha fluxes

    • 12 + log (O/H) = 7.95± 0.05

    • log (N/O) = -1.11 ± 0.08

  •  0.4 dex higher than expected!


Ngc 1741 mkn 1089

NGC 1741 (Mkn 1089)

  • NGC 1741 is the main member (A+C) in Hickson Compact Group 31

  • A very luminous WR galaxy

  • A merger in progress!!

  • Optical spectrum ([email protected])

    • We detect the WR bump

    • Direct estimation of Te, Ne and C(Hb)

    • 12+log (O/H) = 8.22± 0.05

    • log (N/O) = -1.12 ± 0.10

  •  Typical values!

López-Sánchez, Esteban & Rodríguez (2004a), ApJS


The galaxy ngc 5253

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 [email protected]

    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


Ngc 5253 deep vlt echelle spectroscopy

A

B

C

D

NGC 5253: Deep VLT echelle spectroscopy

  • Four 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.

NGC 5253 – WFPC @ HST

UV (blue) + H (green) + [S II] (red) Combined by Á.R. López-Sánchez

H contours over the 2200 Å continuum image (Kobulnicky et al. 1997) and our VLT slit position.

López-Sánchez, Esteban, García-Rojas, Peimbert & Rodríguez 2007, ApJ 656, 168

and López-Sánchez PhD Thesis


Ngc 5253 deep vlt echelle spectroscopy1

12+log O/H = 8.18 log N/O = – 0.91

12+log O/H = 8.28 log N/O = – 1.50

NGC 5253: Deep VLT echelle spectroscopy

  • Our deep VLT spectra CONFIRM the strong N overabundance in a particular zone and also suggest He enrinchement.

  • The comparison of our empirical stellar yields with

    • those obtained by stellar evolution models(Meynet & Maeder 2002)

    • empirical yields for ring nebulae associated to Galactic WR stars (Esteban et al. 1992)

      indicates that few WR stars CAN PRODUCE the observed N and He pollution

  • The amount of enrichment material needed is consistent with the mass lost by the number of WR stars estimated.

López-Sánchez et al. 2007, ApJ 656, 168


Ngc 5253 deep vlt echelle spectroscopy2

NGC 5253: Deep VLT echelle spectroscopy

[O III]

Ha

[N II]


Ngc 5253 h i radio data

NGC 5253: H I radio data

New radio data of NGC 5253 from the LVHIS (Local Volume HI Survey) project using three 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)


Ngc 5253 h i radio data1

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

    López-Sánchez, Koribalski & Esteban 2007 and Kobulnicky & Skillman 2008

H I velocity field:

Rotating about the optical MAJOR axis?


Local starburst galaxy ic 10

Local starburst galaxy IC 10

  • Starburst in the Local Group at ~660 kpc

  • 12+log (O/H) = 8.26(Garnett 1990)

  • A lot of WR stars! (26 studied byCrowther et al. 2003)

  • A good place to look for localized N enrichment!


Local starburst galaxy ic 101

Local starburst galaxy IC 10

WR

  • Optical 3D spectra: PMAS@ 3.5m CAHA

    • 1”/pix, 0.8 A/pix

    • Detected WR signatures (WR-24 A, Crowther et al. 2003)

    • No detection of weak auroral lines (or affected by an ugly Hg emission line!)

    • But the maps do not show any evidence of localized N enrichment 

López-Sánchez, López-Martín, Mesa-Delgado & Esteban, 2008, in prep.


Nitrogen excess in starburst galaxies chemical enrichment via winds of wolf rayet stars

NGC 1512

NGC 1510

  • NGC 1512:

    • SB(r)ab,

    • Z ~0.7 Zo

    • D = 9.5 Mpc

    • Many SF regions (Ha and UV-rich)

  • NGC 1510:

    • S0, BCD, WR

    • 5’ = 13.8 kpc from NGC 1512

      12+log(O/H) ~ 7.95

      log(N/O) ~ -1.2

      Using data provided by Storch-Bergmann+ (1995)

  •  0.3 dex higher than expected!

  • ATCA H I mosaic(3.1 days integr. time)

  • Interaction features!!

  • Koribalski, López-Sánchez & McIntyre (2008, sub.)


Conclusions i

NGC 5253 A

Mkn 1089

UM 420

X

NGC 1510

NGC 5253 C

Conclusions (I)

Data of more galaxies with enough spectral and spatial resolution to get more definitive results (WORK IN PROGRESS)


Conclusions ii

Conclusions (II)

The multiwavelength analysis of a sample of Wolf-Rayet galaxies (López-Sánchez PhD, 2006; López-Sánchez & Esteban 2008) revealed that the majority of them (17 up to 20) show interaction features. New deep data are confirming this result in other WR galaxies.

  • Are interactions between dwarf objects the main triggering mechanism of starbursts, specially in BCDGs?

  • Is this fact related with the detection of N enrichment only in WR galaxies? (Very localized and short event consequence of the recent pollution of the WR winds?)


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