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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)

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Presentation on theme: "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)"— Presentation transcript:

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 Gas rich Metal poor “simple” HII galaxies

3 What do we want to do? 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. We want to determine the detailed physical link between SSCs and the ionized gas in starburst galaxies.

4 NGC5253 (HST-ACS, I+H+B, program 10609, P.I.: Vacca) Very near; z= , D=3.8 Mpc Scale=18.4 pc/” Z~0.30 Z  M B = M(HI)=1.4x10 8 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]… t exp = 5x1500 s each configuration

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

6 Extinction and electron density (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 c1+c2 HII-2 HII-1 UV-1 mean = 130 cm -3 median = 90 cm -3 range = 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

7 Diagnostic diagrams [OIII]/H [SII]/H [NII]/H

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 (Kobulnicky et al. 1997) How much Helium do we have?

12 The He abundance (II) He + /H~ And what about the He ++ ? Once what detected but not any more. (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. Not enough

13 Kinematics (I)

14 Kinematics (II)

15 Ionization in the kinematic components:

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.

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

19 Next step

20 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 n e from the HII region (790 cm -3 ) outwards. [ArIV] lines trace the areas of highest n e ( 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.

21 Extinction in NGC5253 (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

22 Extinction in NGC5253: gas vs. stars E(B-V) stars ~0.33 E(B-V) gas

23 Electronic density mean = 130 cm -3 median = 90 cm -3 range = 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 c1+c2 HII-2 HII-1 UV-1

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25 GIRAFFE: The spectrograph OzPoz: The fiber positioner 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]… t exp = 5x1500 s each configuration

26 What do we want to do? 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. We want to determine the detailled physical link between SSCs and the ionized gas in 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

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

28 An sketch for the giant HII region

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

30 The issue of the d.a.r. (II) HHHH

31 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 We might lose light at some s Or we have to observe at parallactic angle With an IFU The information is recorded but, maybe, in a different spaxel


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