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.)

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

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.

NGC5253

(HST-ACS, I+H+B,

program 10609, P.I.: Vacca)

• 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

First look: Where are we?

F814W

F656N

(HST-ACS, program 10609, P.I.: Vacca)

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

+0.7

+0.0

+1.4

+0.8

+0.9

+1.4

c1+c2

HII-2

HII-1

UV-1

• 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

Diagnostic diagrams +0.9

-0.4

-0.5

-1.4

-0.7

-1.5

[OIII]/H

[SII]/H

[NII]/H

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.

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

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).

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?

The He abundance (II)

-1.8

-2.5

He+/H~0.08-0.09

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

Kinematics (I)

Kinematics (II)

Ionization in the kinematic components:

+1.10

+0.40

-0.55

-1.70

-0.75

-1.70

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.

The end

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

Next step

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.

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

+0.7

+0.0

+0.7

+0.0

Extinction in NGC5253: gas vs. stars

+0.7

+0.0

+0.3

-0.5

E(B-V)stars ~0.33 E(B-V)gas

Electronic density

+1.4

+0.8+0.9

+1.4

• 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

c1+c2

HII-2

HII-1 UV-1

FLAMES@VLT

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]…

• texp = 5x1500 s each configuration

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

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

An sketch for the giant HII region

The issue of the d.a.r. (III)

H

H

The issue of the d.a.r. (II)

H H

1.75-1.54 1.54-1.39 1.39-1.28

1.28-1.19 1.19-1.13

1.11-1.07 1.07-1.04 1.04-1.02

1.02-1.00 1.00-1.01

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