Circumstellar Environments
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Circumstellar Environments. The Team. Historical Group (from IRA-Noto): G.Umana, C.S. Buemi INAF-OACt C. Trigilio INAF-OACt and Università di Catania P. Leto INAF-IRA, Noto. PhD students: L. Cerrigone, CfA-Università di Catania

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Circumstellar Environments

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Circumstellar environments

Circumstellar Environments


Circumstellar environments

The Team

Historical Group (from IRA-Noto):

G.Umana, C.S. Buemi INAF-OACt

C. Trigilio INAF-OACt and Università di Catania

P. Leto INAF-IRA, Noto

PhD students:

L. Cerrigone, CfA-Università di Catania

S. Dolei, P. Manzitto, C. Siringo Università di Catania

Collaborators:

F. Leone, Università di Catania

J. Hora, G. Fazio, M. Marengo SAO-CfA

C. Burigana INAF-IASF

H. Olofsson OSO, G. Giardino (ESA), R. Paladini (JPL)


Circumstellar environments

The project

The study of circumstellar environments

by means of radio observations

  • Radio techniques very useful in multi-frequency

    approaches

  • Unique for some classes of Galactic objects

  • Circumstellar environments:

    • Coronae around active stellar systems

    • Stellar Magnetosphere

    • Stellar ejecta, late stage of stellar evolution


Circumstellar environments

The project

Funds (since 2004):

Besides normal (small) INAF science funding….


Circumstellar environments

Radio Emission from CP stars

  • Anomalous abundances

  • Strong (>3000 G) dipolar magnetic field

  • Variability (continuum, lines, B)

  • - Oblique Rotator Model

radio

Explained in terms of oblique rotator model

Radio emission (also variable ) consistent with

Gyrosynchrotron plus a coherent component


Circumstellar environments

Radio Emission from CP stars

Goal

Understanding the origin of variable radio emission from CP

Method

By modeling the radio flux density light-curve

VLA and ATCA project (multi-frequency, multi-configuration)

Principal Results:

  • Full coverage of radio curve at different frequency for

  • 3 stars

  • Development of a 3D code to reconstruct the

  • magnetosphere of CP and modeling of radio light curve

  • Discovery of a new component in the radio emission

  • Use of coherent emission as a period marker


Circumstellar environments

The 3D code for radio emission

-Gyrosynchrotron from the magnetosphere

18 cm, 4 cm, 1 cm

Good agreement with observations

Trigilio C., Leto, P., Umana, G., Buemi, C., Leone, F., 2004

Leto P., Trigilio, C., Buemi, C. Umana, G., Leone, F. ,2006


Circumstellar environments

CU Vir: the coherent radio component

Discovery of a new component of radio emission:

  • occurring only at particular rotational phases

  • 100% circularly polarized

  • highly directive

  • persistent over years

Consistent with

Cyclotron Maser Emission


Circumstellar environments

CU Vir: the coherent radio component

Consistent with

Cyclotron Maser Emission

  • occurring only at particular rotational

  • phases

  • persistent over years

Marker of the rotational period

CU Virginis is slowing down

dP/dt ~ 10-9 s yr-1

Trigilio C., Leto, P., Umana, G., Buemi, C., Leone, F., 2008


Circumstellar environments

Stellar Ejecta

Observed around stellar objects in late evolutionary phases:

-AGB PNe

Mass-loss  CSE

-LBV

  • Open questions:

  • Shaping: mass-loss (asymmetric) or evolution in an asymmetric

  • environment?

  • Mass and T (gas & dust content)

  • Multiple components (different mass-loss episodes?)

  • Chemistry and its evolution with time (photodissociation, shocks)

  • Chemical evolution of Galaxy (processed material return to ISM)

  • Ideal laboratory to study wind/shocks interaction with ISM


Circumstellar environments

O B A F G K M

MMS 1 -8 Mo

Stellar Ejecta: AGB PNe

104 L

102 L

1 L

10-2 L

10-4 L

yrs

~800

~1000

UV

* Visible

IR

IR-farIR

IR-radio


Circumstellar environments

Hunting for Young PNe

Goal

Understanding the shaping of PNe, through observation of YPNe where the shaping mechanism is still active

Method

Select a sample of TO (AGBPNe) objects; Detect radio to find YPNe

  • far-IR characteristics (excess)

  • Optical characteristics

    • B spectral type

    • spectral and photometric variability

-The onset of ionization can be marked by the presence of free-free emission…

VLA and ATCA project (multi-frequency, multi-configuration) 42 objects

Principal Results:

  • Detected 17 sources; Established their evolutionary status (YPNe)

  • Other 25 objects are genuine hot post-AGB stars.

  • Radio spectra consistent with a PN in the early stage of its

  • evolution

  • High-resolution mapping Bi-polar morphology


Circumstellar environments

YPNe: sub-arc observations

Radio morphology: bi-polar

shaping is already active!

VLA-A, 3.6cm

1

Cerrigone,L., Umana, G., trigilio, C., Buemi, C., Leto, P. ., 2008


Circumstellar environments

IRAS 22568+6141

Umana, G., Trigilio, C., Cerrigone, L., Buemi, C., Leto, P., 2008

VLA-A, 3.6cm

VLA-C, 3.6cm

1

Total flux= 32mJy

Central component 1.65 0.05 mJy

Consistent with stellar wind? (Mass-loss)

new VLA, high resolution, multi-frequency data already available (AU119), waiting for reduction!

H-alpha


Circumstellar environments

CSE: the dust component

Goal

Understanding the dust contribution to the shaping

Method

Inspecting the dust properties of envelope in TO (AGBPNe) objects:

-systematic differences between radio detected (YPNe) and post-AGB?

SST project on YPNe, part of the SST-GTO on Stellar ejecta (PI G. Fazio)

IRAC + IRS observations of 42 TO (with radio infos)

Principal Results:

  • CSE around TO generally very compact (not resolved by IRAC)

  • IRS spectra dominated by thermal dust emission plus spectral

  • structures due to dust (crystalline silicates)

  • besides recombination lines, no evident differences between radio (YPNe)

  • and not radio detected (hot post-AGB) objects.

  • about 50% of the sample shows mixed chemistry

  • necessity to introduce big grains to fit SEDs


Circumstellar environments

Silicates

[NeII]

[ArII]

PAH

PAH

Silicates

The dust component: Results

When SED (up to mm) are modeled:

- necessity to consider multi-component CSE

- big grains (0.05-100 m)

- IRS spectra dominated by thermal dust emission plus spectral

structures due to crystalline silicates

- part of the sample shows mixed chemistry: not consistent with evolution theory

-Consistent with a reservoir of O-rich material, probably

an equatorial disk (PPNe Red Rectangle)

 strong clue for stellar ejecta being collimated by

such structures!

Cerrigone, L., Hora, J., Umana, G., Trigilio, C., 2007

Cerrigone, L., PhD Thesis, 2008


Circumstellar environments

MMS > 25 Mo

Stellar Ejecta: LBV

  • log L/L ~ 5.0-6.3

  • strong mass-loss

    ~ 10-6÷10-4 Myr-1

  • Variability

  • Outbursts ΔV ~ 1-2 mag


Circumstellar environments

LBVs: the ionized gas

Understanding the LBV phenomenon through the study of their ejecta (morphology and physics of the nebula)

Goal

Determine the properties of the radio emission, tracing the ionized gas component of the ejecta

-Symmetric versus Asymmetric morphology

- Mass-loss of the central objects (current-day mass-loss)

Method

VLA Multi-frequency, multi-configuration project

Principal Results:

  • Radio morphologies in general asymmetric and structured

  • High-resolution allows to resolve the core component

  • High-resolution, multi-frequency allows to determine mass-loss

  • Radio observations more efficient than usual H (no extinction)

  • essential to probe the ionized component in strongly reddened object


Circumstellar environments

IRAS 18576+0341

LBVs in Radio

Probing the ionized component in a very dusty environment

Strongly reddened object: no optical counterpart

VLA-A, C-band

-Multi-frequency, high resolution VLA observations:

-a core component (LBV’s wind)

-an extended, asymmetric nebula

Current day mass-loss

3.7 10-5Myr-1

B0-B0.5 I, Teff ~ 2.6 104 K

Umana, G., Buemi, C.S., Trigilio, C. , Leto, P. et al., 2005


Circumstellar environments

LBVs: the dust component

Understanding the LBV phenomenon through the study of their ejecta (morphology and physics of the nebula)

Goal

Determine the properties of the mid-IR emission, tracing the dust component of the ejecta

-Symmetric versus Asymmetric morphology

- Comparison with ionized gas component to derive clues for shaping

Method

[email protected] project

multi-frequency sub-arcsec imaging

Principal Results:

  • Ejecta morphologies: highly structured

  • Thermal dust morphologies DIFFERENT from radio.


Circumstellar environments

11.26 m

12.27 m

17.65 m

IRAS 18576+0341

Mapping with [email protected] scale 0.075

[email protected]


Circumstellar environments

IRAS 18576+0341

Comparison between ionized gas and dust: sub-arcsec mapping

4

VLA-A, 5 GHz (6cm)

VISIR 12.25 m

-4

Clues on mass-loss and shaping:

A) Mass-loss can occur asymmetrically; outflows may be shaped by dusty structures

B) dust distribution not homogeneous

dust competes with gas in absorbing UV radiation: holes in dust allow gas to glow!


Circumstellar environments

LBVs: ionized gas and dust comparison

VLA-A 3.6cm

VISIR 12.25 m

Different situation in HD168625

- The ionized gas appears contained by dust:

- Outflow channeled by a dusty equatorial torus??

kinematical information necessary!


Circumstellar environments

LBV: more on the dust component

Goal

Determine the characteristics of dust component: yield to ISM

Chemistry; mass-loss history

Method

Determine mid-IR spectral and morphological properties

Modeling the SEDs (CLOUDY)  Mass-loss history

-SST project on Galactic LBVs, part of the SST-GTO on Stellar ejecta (PI G. Fazio)

IRAC+IRS (low + high res) of nine Galactic LBV

-SAGE Collaboration on LBVs in MCs (IRAC+IRS+MIPS)

First Results:

  • Dusty CSE around Galactic LBV can be very extended

  • Both regular (spherical) and asymmetric morphology observed.

  • IRS spectra: dominated by emission lines and dust spectral features (PAHs)

  • [Fe II] mid-IR lines detected: possible diagnostics for shocks


Stellar ejecta

Stellar ejecta

Wray17-96

SST-IRAC mosaic

IRAC LBV GTO program


Circumstellar environments

Stellar ejecta: the future

In the next years new instrumentations will come on-line

ALMA: mm interferometer ( 30-900 GHz)

spectral and continuum capabilities (sub-mJy) ,

sub-arcsec imaging 2011

EVLA: cm interferometer (1.4-50 GHz) :

spectral and continuum capabilities (sub-mJy) ,

sub-arcsec imaging 2009


Circumstellar environments

Stellar ejecta:the future

Stellar ejecta possible foregrounds for CMB:

- from a feasibility study ~400 CSE will be detected

by PLANCK (Umana, G. Burigana, C., Trigilio, C.- 2006)

- PLANCK will provide flux measurements, between 30

and 900 GHz, for the radio brightest PNe SEDs

Umana, Leto, Trigilio, Buemi, Toscano, Manzitto, Dolei,

Cerrigone, 2008

(based on 43 GHz single dish INAF-IRA teleacope Obs)

PLANCK mission,

full sky coverage

(30 to 900 GHz)-end 2008


Circumstellar environments

Stellar ejecta:ALMA

  • ALMA will provide detailed (sub-arcsec, sub-mJy) maps of:

  • ionized gas continuum (30 GHz…..) morphology

  • molecular gas CO (100 GHz) morphology (Kinematic)

  • dust continuum (100 GHz…) morphology

Morphological and spectral studies of different components coexisting in the ejecta  CLUES on shaping

ionized gas continuum

continuum (1.4-50 GHz)

RRLs (1.4-50 GHz)

molecular gasCO

H2 (near-IR)

Dust continuum

continuum (mid-IR)

SYNERGIES

ALMA(sub-arc, sub-mJy)

[email protected] (sub-arc, mJy)

HST (sub-arc)

EVLA (sub-arc, sub-mJy)


Circumstellar environments

ALMA-2011+…… putting together the pieces

Radio jet that makes its way through the CO cocoon

Dusty disk/torus

Molecular Cocoon


Circumstellar environments

Stellar ejecta:ALMA

mm and submm observations provide strong constraints for SED modeling

Post-AGB stars

mm obs [email protected] 30m

+ SEDs modeling (DUSTY):

 = 0.9-1.6

R =1016 10 17 cm

dM/dt~ 10-6-10-5

ALMA: Detailed maps of CSE dimension, structure…

VERY strong constraints to the SED Modeling!

Buemi, C, Umana, G., Leto,P., Trigilio, C 2007


Circumstellar environments

The link to the Catania University

Radioastronomy (C. Trigilio) Undergraduate course (Physics)

Galactic Radiosources (G. Umana) Lectures for PhD program

All the students trained at INAF-IRA 32m Radiotelescope:

acquisition techniques,

data reductions …..

PhD students:

L. Cerrigone, Infrared and Radio properties of YPNe

CfA-Università di Catania Thesis defence next February

P. Manzitto, SEDs modeling of PNe

Università di Catania, III year

C. Siringo,SiO maser in CSE

Università di Catania, begin III year

S. Dolei, Radio modeling of PNe

Università di Catania, begin II year

Science for ALMA

Science for ALMA

PLANCK, HERSCHEL

Science for ALMA

Science for ALMA

PLANCK, HERSCHEL


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