BULGES
NGC 4594 NGC 4710 ESO 498-G5
ESO 1129 NGC 7457 NGC 4565 FORMATION AND EVOLUTION OF BULGES Classical bulge Presents in early type galaxies: lenticular, Sa
Very similar to elliptical : Mg2 - ; Dn - ; FP; SSP, R(1/4)
Some differences: fotometry shows young stellar populations
Formation trough dissipative collapse or merger events (theoretical)
Pseudobulge
Presents in late type galaxies: Sb and later type
Luminosity profile is exponential
They are flat component, with a disk kinematic
Star formation
Formed trough secular evolution slow rearrangement of disk material indicate no major merger (theoretical)
Boxy/peanuts bulge
boxy/peanut bulges are parts of bars seen edge-on, have their origin in vertical instabilities of the disc and are somewhat shorter in extent than bars.
Their stellar population is similar to that of the inner part of the disc from which they formed. FORMATION AND EVOLUTION OF BULGES
Eggen et al. 1962 Kauffmann 1996 Sandage 1990 Baugh et al. 1996 Gilmore & Wyse 1998 Cole et al. 2000 Classical Bulges
Aguerri et al. 2001 Disk-like Bulges Fu et al. 2003 Athanassoula 1992 Eliche-Moral et al. 2006 Heller & Shlosman 1994 Shen & Sellwood 2004
Boxy/Peanut Bulges Raha et al. 1991 Debattista et al. 2004 Martínez-Valpuesta et al. 2006 FORMATION AND EVOLUTION OF BULGES
IN THE CURRENT PARADIGM… Dissipative collapse Merging events Secular evolution
Classical Bulges Disk-like Bulges Which is the relative importance of different mecchanism (is one dominant?) Different formation mechanism leave differences in the stellar populations and in their radial profiles Model predictions… Absent (or very shallow) Gradients eventualy present could Presence of metallicity and gradients in bulges (Bekki either be amplified (change of α/Fe gradient (Kobayashi & Shioya 1999) scalelength) or erased (disc heating) 2004). (Moorthy & Holtzman 2006) metallicity gradient rarely Presence of metallicity enhanced by secondary gradient with flat profile of events of star formation More constraints from comparison α/Fe (Pipino et al. 2008). (Hopkins et al. 2009). of stellar populations of disk and bulge ENVIRONMENT
STELLAR POPULATION RELATED WITH THE ENVIRONMENT WHERE THE GALAXY FORM AND EVOLVE
CLUSTER
Potential wheel formation stop the merging in cluster (Z >2) Bought et al 1996
FIELD Merging continue (Z < 1)
FIELD GALAXIES YOUNGER THAN CLUSTER COUNTERPART
OBSERVATION (elliptical and early type): EXTENDED DATA FIELD YOUNGER AND HIGHER METALLICITY De la rosa et al. 2001 , Collobert et al 2006
CENTRAL VALUES NO DIFFERENCES BETWEEN CLUSTER AND FIELD GROUP Bernardi et al. 1998 Central values and Environment Late type gradients …STEP BY STEP……
GALAXIES SAMPLE SELECTION
14 BRIGHT, NEARBY, CLUSTER, GALAXIES
OBSERVATION AND DATA REDUCTION
STANDARD REDUCTION FOR LOW RESOLUTION DATA AQUIRED WITH [email protected]
PHOTOMETRIC ANALYSIS 2D PHOTOMETRIC DECOMPOSITION TO DISENTAGNGLE BULGE FROM DISK
KINEMATIC AND LINESTRENGTH ANALYSIS 1) ROTATION GALAXY VELOCITY AND ROTATION VELOCITY DISPERSION MEASURED 2) LINE STRENGTH OF LICK INDICES MEASUERED USING WORTHEY ET AL. 1994 DEFINITION
RESULTS…… Consistency of results
Comparison with the lick system..
Comparison with litterature MAJOR AXIS KINEMATICS AND LINE-STRENGTH
Rbd Rbd Rbd Nuclear region
Bulge dominated region POPULATIONSSTELLAR THE OF ANALISYS
Disc dominated region …RESULTS……
CENTRAL VALUES
AGE METALLICITY AND /ENHANCEMENT
RADIAL PROFILES
AGE METALLICITY and /ENHANCEMENT
PSEUDOBULGES
NGC 1292 CONCLUSIONS
LINE STRENGTH CENTRAL VALUES 1) The value of /
LINE STRENGTH PROFILES 1) Most of the sample galaxies show no gradient in age (merging events ) but a negative gradient of metallicity. (dissipative collapse) 2) no gradient was measured in the [α/Fe] radial profiles for all the galaxies (No inside-out scenario expected from merging)
Star formation fast and homogeneus in the bulge CENTRAL VALUES: H, Mg2,
IN ELLIPTICAL GALAXIES STRUCTURAL PROPERTIES CORRELATE
CHEMICAL PROPERTIES Mg2, H, Fe
IN LATER TYPE ?
We found good Mg2, H still correlate correlation for
Hint they are steeper… AGE AND METALLICITY CENTRAL VALUES
3 Gyr 12 Gyr
Model grids from Thomas et al. 2003 AGE AND METALLICITY CENTRAL VALUES
Hint that early type are older and metal richer than later type Very young
Young
Old
3 Gyr 12 Gyr T ≤ 0 Model grids from Thomas et al. 2003 T > 0 AGE AND METALLICITY CENTRAL VALUES
Fornax No relation found with Pegasus morphological type NGC 7582 No relation found with the membership
3 Gyr 12 Gyr
Model grids from Thomas et al. 2003 AGE AND METALLICITY CENTRAL VALUES
No relation found with morphological type Young No relation found with the membership Very young 3 clear different classes of ages
Relation age-metallicity
Most of objects show solar value of /Fe while few have super solar /Fe Old
Important correlation with the central velocity rotation dispersion
More massive bulges are older, more metal rich AGE AND METALLICITY RADIAL PROFILES
Metallicity is Bulges Jabloka et al. 2007 decreasing with Early-type Mehlert et al. 2003 the radius
Age shows no gradient
Grad[Z/H] = [Z/H] (center)- [Z/H] (1Rbd) (Mehlert et al. 2003)
Grad(Age) = Age (center)-Age (1Rbd) (Mehlert et al. 2003) Collapse model produce metallicity gradient AGE AND METALLICITY RADIAL PROFILES
No gradient found with the radius
Solar to super-solar value (result from central value)
Grad( /
Merger model do not produce gradient and produce solar /
BRIGHT (BT < 15.5 Mag) NEARBY GALAXIES (cz<4500 km s-1)
MORPHOLOGICAL TYPE: SPIRAL GALAXIES
14 CLUSTER GALAXIES ( Ferguson 1989; Garcia 1983) Fornax, Eridanus, Pegasus, N7582 SPECTROSCOPIC OBSERVATIONS 2 RUNS AT [email protected] TELESCOPE
WAVELENGTH RANGE = 4700-6700 Å
DISPERSION = 1.98 Å/PIXEL
INSTRUMENTAL FWHM 6 Å
SPATIAL RESOLUTION = 0.314 ARCSEC
Calibration and Observation
BASIC CALIBRATION (bias, flat, HeAr calibration lamp)
SPECTRA TAKEN ALONG THE MAJOR AXIS
TYPICAL EXPOSURE TIME 2x3600 s S/N>35-40
2-5 LICK/VELOCITY STANDARD STARS (G, K spectral type) KINEMATICS AND LINESTRENGTH
KINEMATICAL MEASUREMENTS We measured the profiles along the major axis of the values of the rotation velocity (v), rotation velocity dispersion ()
LINE STRENGTH MEASUREMENTS We measured the values of the indices defined in the LICK/IDS system for all the those present in our range
They are => H, Fe5015, Mg1, Mg2, Mgb, Fe5270,Fe, 5335, NaD Worthey et al.1994 Molecular indices Atomic indices
2 2 1 F FI I EW 1 d EW 2.5log 1 d 1 2 FC F 1 1 C LICK INDICES OVERVIEW Lick indices related with age metallicity and /Fe
Balmer lines (H, H …) Stellar population age
The iron and magnesium lines Metallicity
Mg/
Possible way to break the degeneracy…
MgFe Mgb (0.72 Fe5270 0.28 Fe5335 (Whortey et al. 1994, Thomas et al.2003) PSEUDOBULGES - THE CASE OF NGC 1292
PSEUDO-BULGES CLASSICAL BULGES
Flattened disk like structures, may resemble little ellipticals
have secondary bars, rings, and/or whic happen to have a spiral structure disc
Dynamically cold – rotation dynamically hot - dominated dispersion dominated
Formed from slow rearrangement of formed via violent disk material – indicate no major relaxation during major merger merger
Secular evolution evolution Secular Usually in types Sbc and later in types S0-Sbc
In globally blue galaxies in globally red galaxies Merging/dissipative collapse Merging/dissipative Kormendy and Kennicut 2004 translate these general concepts in a list cookbook rules (The more apply, the safer the classification becomes) PSEUDOBULGES - THE CASE OF NGC 1292 APPLICATION OF KORMENDY RULES TO OUR SAMPLE S´ersic index (n < 2)
Most of the sample bulges have it (9/14) Ellipticity compared with Vmax/σ0
The apparent flattening of the bulge is PSEUDOBUGES similar to that of the disc NGC 1292, NGC 1351
Outsider in the FJ relation
NGC 1292 satisfy all the conditions
Forbes & Ponman (1999) pseudobulge PSEUDOBULGES - THE CASE OF NGC 1292
STELLAR POPULATION
Radius
CENTRAL REGIONS ARE: YOUNG AGE (T=3 Gyr)
LOW METAL CONTENTS ([Z/H] =-0.7)
OVERABUNDANCE [/Fe]=-0.12
DATING THE FORMATION OF THE COUNTER-ROTATING STELLAR DISC IN THE SPIRAL GALAXY NGC 5719 BY DISENTANGLING ITS STELLAR POPULATIONS COUNTER-ROTATIONS presence of stars/gas counter-rotating with respect to other stars and/or gas
NGC 7217 FEW GAS LOT OF GAS FORMATION OF GAS COUNTER-ROTATIONS
1) Acquisition of gas external origin gas disk built by retrograde acquisitions
internal origin Gas disk built by a bar Subsequent star formation in the acquired gas disk
2) Acquisition of already formed stars and gas external origin merger with other galaxies
internal origin secular evolution with disk instability FORMATION OF GAS COUNTER-ROTATIONS
NGC 2855 FORMATION OF GAS COUNTER-ROTATIONS
1) Acquisition of gas external origin gas disk built by retrograde acquisitions
internal origin Gas disk built by a bar Subsequent star formation in the acquired gas disk
2) Acquisition of already formed stars and gas external origin merger with other galaxies
internal origin secular evolution with disk instability
Expected observables
1) Age of the counter-rotating component is younger
2) Age of the counter rotating component younger in the 50% of case Metallicity of gas and stars possibly different
NGC 5719 – DISENTANGLING THE SPECTRA
Flux
wavelength NGC 5719 TEST CASE…
count-stars
gas co-stars NGC 5719 – OBSERVATIONS VIMOS - VIsible MultiObject Spectrograph @UT3
The integral-field spectroscopic observations in service mode
We used the 0.67 arcsec per fiber resolution
Spectral range 4150–6200 Å with a reciprocal dispersion of 0.54 Å/pixel
The instrumental spectral resolution measured at 5200 Å was 2.0 Å (FWHM)
NGC 5719 – DISENTANGLING THE SPECTRA NGC 5719 – 2D FIELD kinematic
count-stars gas
co-stars NGC 5719 – INDICES NGC 5719 – 2D FIELD STELLAR POPULATION
Age Metallicity A/Fe
Corotating
Counter
-
Corotating
NGC 5719 – CONCLUSIONS
5719 is decomposed into the contributions of three distinct kinematic components characterised by a regular disc-like rotation: one main and one secondary stellar component and a ionised-gas component.
The ionised gas is detected all over the observed field of view. It is characterised by a strong Hβ emission, which is concentrated in a twin-peaked morphology indicating an edge-on ring
The contributions of the 2 components to the total light is F(main) = 56% and F(secondary) = 44%
We prove that the mean age of the counter-rotating disc, which is associated to the neutral and ionised gas disc, is indeed younger than the main stellar disc. This result shows that counter-rotating disc has been recently assembled.
The scenario proposed by Vergani et al. (2007) that NGC 5719 hosts a counter-rotating stellar disc originated from the gas accreted during the ongoing merging with its companion NGC 5713, is finally confirmed. NGC 4550 NGC 3593 NGC 4550, NGC 3593 – STELLAR POPULATIONS NGC 5719, NGC 3593, NGC 4550 – CONCLUSIONS
NGC 3593 and NGC 4550 host a counter-rotating stellar disk, which rotates in the same direction as the ionized gas, and which is on average less massive, younger, metal poorer, and more α enhanced than the main stellar galaxy disk.
NGC 3593: counter rotating stellar disk is younger than the main disk
NGC 4550: counter rotating stellar disk is younger than the main disk
Our results support the scenario of external gas acquisition, followed by a subsequent outside-in star formation as the origin of the observed counter-rotation.
The merger scenario cannot be completely ruled out, given the low statistics available. Counterotation – next step
Large survey of the north and south sky to oberve all the galaxy with hints of counter rotations. Candidates for the north are chosen with [email protected] Asiago telescope. SOUTH NORTH
VIRUS-P@VLT
VIMOS@VLT