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A detailed 2D spectroscopic study of the Central Region of NGC 5253

A detailed 2D spectroscopic study of the Central Region of NGC 5253. Ana Monreal Ibero (1). Jos é Vílchez (1) , Jeremy Walsh (2) , Casiana Muñoz-Tuñón (3) (1) IAA, (2) ESO, (3) IAC. (based on Monreal-Ibero et al. 2010, A&A, 517, 27 and Monreal-Ibero et al. 2011, Ap&SS, in prep.).

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A detailed 2D spectroscopic study of the Central Region of NGC 5253

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  1. A detailed 2D spectroscopic study of the Central Region of NGC 5253 Ana Monreal Ibero(1) José Vílchez(1), Jeremy Walsh(2), Casiana Muñoz-Tuñón(3) (1)IAA,(2)ESO,(3)IAC (based on Monreal-Ibero et al. 2010, A&A, 517, 27 and Monreal-Ibero et al. 2011, Ap&SS, in prep.)

  2. Starburst galaxies • Starburst: ~hundreds M yr-1 of gas are transformed into stars in an small region in the nuclei of galaxies • Important impact on the host galaxy. Main contributors to the enrichment of the ISM. • Some of them expell material into the IGM: the SGW • Nuclear starburst • Blue Compact Dwarfs • (U)LIRGs HII galaxies • Gas rich • Metal poor • “simple”

  3. What do we want to do? We want to determine the detailed physical link between SSCs and the ionized gas in starburst galaxies. • Analyse the physical (extinction, ionization and electron density structure…) and chemical conditions of the ionized gas. • Analyse the kinematics of the gas using v and  maps from H (or H) and [OIII]5007, etc. • Identify the SSCs responsible of the gas structure.

  4. NGC5253 • Very near; z=0.001358, D=3.8 Mpc • Scale=18.4 pc/” • Z~0.30 Z • MB=-17.13 • M(HI)=1.4x108 M • Filamentary structure • Hints of inflows/outflows • Observed in every spectral range Let´s look at it with FLAMES • scaling: 0.52”/spa; f.o.v.: 11.5”x7.3” • L479.7 (R=12000)  Hβ+[OIII]… • L682.2 (R=13700)  Hα+[NII]+[SII]… • texp = 5x1500 s each configuration (HST-ACS, I+H+B, program 10609, P.I.: Vacca)

  5. First look: Where are we? F814W F656N (HST-ACS, program 10609, P.I.: Vacca)

  6. Extinction and electron density +0.7 Peak of extinction doesn´t coincide with optical nucleus but with the dominant source in IR, the very reddened C2 from Alonso-Herrero (Contours: HST-NICMOS, F160W, Alonso-Herrero 2004) +0.0 • mean = 130 cm-3 • median = 90 cm-3 • range = 30 - 790 cm-3 • giant HII region -> ~400 cm-3 • integrated = 180 cm-3 +1.4 +0.9 • c1+c2-> 6200 cm-3 • HII-2 -> 6100 cm-3 • HII-1 -> 4200 cm-3 • UV1-> 3300 cm-3 • Integrated = 4520 cm-3 HII-2 +1.4 c1+c2 UV-1 +0.8 HII-1

  7. Diagnostic diagrams +0.9 [OIII]/H -0.4 -0.5 [SII]/H -1.4 -0.7 [NII]/H -1.5

  8. Where do we have extra Nitrogen? The area of nitrogen enrichment covers the giant HII region + the tongue-shaped extension towards SE + the tongue-shaped extension towards the NW.

  9. The Wolf-Rayet population (I) • WR: Very bright objects with broad emission line in their spectra • WN: lines of Helium and Nitrogen • WC: lines of Helium, Carbon and Oxygen • Result of the evolution of O-stars • They date very precisely the age of the stellar population where they are found Blue bump  Red bump  The WR population in NGC5253 has already been studied in specific areas (e.g. Schaerer et al. 1997, 1999) For the moment they are the best candidates for causing the Nitrogen enhancement. Other possibilities: LBVs, PNe, late O-stars We can map the location of the WR population without any bias due to the slit position to check if it does coincide with the “N-enhanced” area

  10. The Wolf-Rayet population (II) WR features are distributed in an irregular manner in an area much larger than and not always coincident with the one enriched with Nitrogen In general, WR are not necessarily the cause of this N-enrichment. (Possible exception: the SSCs at the nucleus and the two extensions).

  11. The He abundance (I) “WR causing the N-enrichement” only consistent with a given quantity of Helium We need He/H~0.12 How much Helium do we have? (Kobulnicky et al. 1997)

  12. The He abundance (II) Not enough He+/H~0.08-0.09 -1.8 And what about the He++? Once what detected but not any more. -2.5 (Campbell et al. 1986) We have found some (He++/H<0.005!) BUT • It is not enough • It does not always spatially coincide with the WR emission and/or the “N-enhancement” areas.

  13. Kinematics (I)

  14. Kinematics (II)

  15. Ionization in the kinematic components: +1.10 +0.40 -0.55 -1.70 -0.75 -1.70

  16. Summary of the GHIIR • Larger extinction in the upper part of the f.o.v. • Larger density in the upper part of the f.o.v. • 2 narrow components in the lower part of the f.o.v. • 1 narrow component in the upper part of the f.o.v. • 1 broad component relatively symetric with respect to the central clusters. • Offsets in velocity in [NII] (and [SII]) for the broad component. Also “reversed” offsets for the narrow component. • The broad components seems to have ~1.5 times more excess in N than the narrow one.

  17. The end (based on Monreal-Ibero et al. 2010, A&A, 517, 27 and Monreal-Ibero et al. 2011, Ap&SS, in prep.)

  18. Next step

  19. Summary • The largest extinction is associated with the giant HII region. The peak of extinction is offset by 0.5” from the peak of emission in the continuum. • [SII] lines indicate a gradient of ne from the HII region (790 cm-3) outwards. [ArIV] lines trace the areas of highest ne (4200-6200 cm-3). • N-enhancement is located in the whole HII region peaking (more or less) at the peak of extinction. • WR population is distributed over a much wider area. • The He that we find is not enough to explain the N-enhancement with WRs.

  20. +0.7 +0.0 Extinction in NGC5253 +0.7 +0.0 (Contours: HST-NICMOS, F160W, Alonso-Herrero 2004) Peak of extinction doesn´t coincide with optical nucleus but with the dominant source in IR, the very reddened C2 from Alonso-Herrero

  21. +0.7 +0.0 +0.3 -0.5 Extinction in NGC5253: gas vs. stars E(B-V)stars~0.33 E(B-V)gas

  22. Electronic density +1.4 +1.4 HII-2 c1+c2 UV-1 HII-1 +0.9 +0.8 • mean = 130 cm-3 • median = 90 cm-3 • range = 30 - 790 cm-3 • giant HII region -> ~400 cm-3 • integrated = 180 cm-3 • c1+c2-> 6200 cm-3 • HII-2 -> 6100 cm-3 • HII-1 -> 4200 cm-3 • UV1-> 3300 cm-3 • Integrated = 4520 cm-3

  23. GIRAFFE: The spectrograph OzPoz: The fiber positioner FLAMES@VLT • MEDUSA • IFU • ARGUS + several gratings We used ARGUS • scaling: 0.52”/spa; f.o.v.: 11.5”x7.3” • L479.7 (R=12000)  Hβ+[OIII]… • L682.2 (R=13700)  Hα+[NII]+[SII]… • texp = 5x1500 s each configuration

  24. What do we want to do? • Starburst: ~hundreds M yr-1 of gas are transformed into stars in an small region in the nuclei of galaxies • Important impact on the host galaxy. Main contributors to the enrichment of the ISM. • Some of them expell material into the IGM: the SGW We want to determine the detailled physical link between SSCs and the ionized gas in starburst galaxies. • Analyse the physical conditions (extinction, ionization and electronic density structure…) of the ionized gas. • Analyse the kinematics of the gas using v and  maps from H (or H) and [OIII]5007. • Identify the SSCs responsible of the gas structure. • Putting all this together to try to understand under which conditions a SGW is created.

  25. Integral Field Spectroscopy Allington-Smith et al. 2000 • Homogeneity • Shorter exposure times Records simultaneously three variables (α, β and ) in two dimensions (x and y)

  26. An sketch for the giant HII region

  27. The issue of the d.a.r. (III) H H

  28. The issue of the d.a.r. (II) 1.39-1.28 1.11-1.07 1.07-1.04 1.04-1.02 1.75-1.54 1.54-1.39 1.28-1.19 1.19-1.13 1.02-1.00 1.00-1.01 H H

  29. The issue of the d.a.r. (I) Differential atmospheric refraction: change of the position of the image of an object in the focal plane with wavelenght due to atmosphere With a slit With an IFU • We might lose light at some s • Or we have to observe at parallactic angle • The information is recorded but, maybe, in a different spaxel

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