PH600 14-15 Project
Prof Michael D. Smith
Centre for Astrophysics & Planetary Science
University of Kent
Towards a resolution of a burning issue in Astrophysics, from the fields of solar
system, galactic or extragalactic astronomy.
Recent problems between observational data and theory provide a rich source
of issues to be investigated. This project will focus on a specific phenomenom
of high interest and motivation, in one of extragalactic astronomy, galactic
astronomy, or solar system astronomy. The study will begin with a review of
recent publications which address the issue and an evaluation of possible
solutions. To achieve this, all major physical processes involved will be
understood in depth and detail. Then, data will be obtained from an appropriate
source and analysed in order to generate, in an original way, fresh evidence for
or against the available solutions. The study will then consider new or hybrid
solutions before considering how these can be tested. The relevance of new
ground-based telescopes or space missions will be discussed.
To understand the nature and importance of planetary nebula.. What are they,
how do they form and disappear?
http://messier.seds.org/planetar.html
Interesting with good references:
http://www.astroscu.unam.mx/apn6/PROCEEDINGS/Santander-Garcia.pdf
To identify the current major issues in this field. To suggest solutions. To
determine the future prospects for progress in this field.
Stage 1. Knowledge.
Do literature review on PN and PPN. What shapes them? What parameters do we
need to model them? Density, wind speed, size? Spherical? Jet? Slow wind? Fast
wind? Superwind?
Use ADS system to perform literature review.
http://adsabs.harvard.edu/abstract_service.html
or to browse latest papers:
http://arxiv.org/list/astro-ph/recent
Stage 2: Understand them.
What are the issues that still need resolving? How do they evolve?
What do they look like at different wavelengths?
Is there a single path or does it depend on some initial consitions such as angular
momentum, magnetic field,…..
PH600 HOMEPAGE:
http://astro.kent.ac.uk/mds/Modules/1415/PH600/
These notes
Kieran Forde thesis on observations)…..
http://star.herts.ac.uk/~kforde/Phd.html
http://www.star.herts.ac.uk/~kforde/phd.pdf
Igor Novikov’s Euromasters Thesis
Chapter 7 .1 of my book is also there: 7.1 PPN
Stage 3: One problem each. The problem – choose one (or more?) from :Physics Project. Are PN in binaries? Are some in binaries? How can we tell? See:
http://www.astroscu.unam.mx/apn6/PROCEEDINGS/Santander-Garcia.pdf
What do PN and PPN contain? Composition? Are the surrounding molecular H2 or
atomic H, and Helium. Dust, magnetic field and metal content and distribution in
environment and in the winds? Radiation processes at different stages?
Gather and plot data from published sources.
Observational Project. How can we recognize a PPN or a PN? Could it be a
protostellar outflow instead? How can we be certain? Projection effects? Where are
they in the galaxy? How many types are there? Use Aladin/AIP software,
http://adsabs.harvard.edu/abs/2012IAUS..283....9P
http://arxiv.org/pdf/1203.1694v1.pdf
http://adsabs.harvard.edu/abs/2014apn6.confE..47K
http://arxiv.org/pdf/1407.4617v1.pdf
Evolution Project. How do PPN evolve from post-AGB to PN? Dynamics: is there
evidence for pulses, precession in the wind or are the winds smooth or explosive?
What does a very young PPN look like? How do PN decay? Can we observe this
phase? Use Aladin/AIP software. Do they become rounder in time?
Stage 4: Develop Hypothesis, try to test by looking for evidence or counterevidence.
Stage 5: Use IDL or MATLAB to analyse simulation of PNe. TBC
Stage 6.Unlikely to be reached. Performing hydrodynamic simulations with
Pluto or ZEUS codes on Mac or UNIX machine using fortran/C and IDL.
Protoplanetary nebula:
Interaction of jets and winds with molecular environments.
Catalogues:
http://heasarc.gsfc.nasa.gov/W3Browse/nebula-catalog/plnebulae.html
http://adsabs.harvard.edu/abs/2014arXiv1407.0109S
Papers on PPN parameters:
http://adsabs.harvard.edu/abs/2009ApJ...698..439D
We present high angular resolution observations of the HC3N J = 5-4 line from
the Egg nebula, which is the archetype of proto-planetary nebulae (PPNs). We
find that the HC3N emission in the approaching and receding portion of the
envelope traces a clumpy hollow shell, similar to that seen in normal carbonrich envelopes. Near the systemic velocity, the hollow shell is fragmented into
several large blobs or arcs with missing portions correspond spatially to
locations of previously reported high-velocity outflows in the Egg nebula. This
provides direct evidence for the disruption of the slowly expanding envelope
ejected during the AGB phase by the collimated fast outflows initiated during
the transition to the PPN phase. From modeling the HC3N distribution, we
could reproduce qualitatively the spatial kinematics of the HC3N J = 5-4
emission using a HC3N shell with two pairs of cavities cleared by the collimated
high-velocity outflows along the polar direction and in the equatorial plane.
http://adsabs.harvard.edu/abs/2005ApJ...624..331H
Observations made with the Heinrich Hertz Telescope of CO millimeter and
submillimeter emission toward a sample of 22 proto-planetary nebula (PPN)
candidates resulted in detections of 12 sources in the CO J=2-1 line. Of these
12, seven sources were also detected in the J=4-3 line. These 4-3 transitions
are the highest yet observed in all but one of these PPNs. Statistical
equilibrium/radiative transfer models were calculated for the CO emission in the
circumstellar envelopes (CSEs), assuming various power-law density
distributions. These models were compared with the intensity and profile shape
of the observed spectra. For the region of the CSE probed by CO emission, the
density laws must be steeper than inverse squared and are consistent with
power laws between ρ~r-3 and r-4. These radial density distributions imply that
the mass loss was not constant but increased during the last part of the
asymptotic giant branch (AGB) phase. Mass-loss rates at the end of the AGB
for the three best-constrained sources are found to be 7.7×10-5 Msolar yr-1
(IRAS 22272+5435), 2.3×10-5 Msolar yr-1 (IRAS 07134+1005), and 1.3×10-5
Msolar yr-1 (IRAS 17436+5003) for the case of ρ~r-3. These time-varying
mass-loss rates can be integrated to calculate the enclosed envelope masses
ejected in the past ~10,000 yr. The ejected envelope masses close to the star
lie in the range 0.02-0.30 Msolar these values are consistent with theoretical
models, which indicate that <20% of the stellar mass loss occurs in the last
10,000 years of the AGB. These results are in contrast to some recent dust
studies based on infrared emission, however, in which much higher envelope
masses are determined. The density laws, mass-loss rates, and enclosed
envelope masses that we derive furnish important constraints for evolutionary
models of stars in the late AGB and during the transition to the planetary nebula
phase.
PPN PHASES ???
with two types of mass loss : an AGB wind (D 10 km
s~1 ) mass-loss phase followed by a briefer but supposedly
more violent superwind (D 20 km s~1 ) mass-loss phase
(Renzini 1981).
In the AGB wind phase, an AGB star loses its mass through
a dust-driven AGB wind (Salpeter 1974; Kwok 1975;
Netzer & Elitzur 1993) in a largely spherically symmetric
manner, creating a spherically symmetric circumstellar
AGB wind shell.
The axisymmetric superwind dumps the envelope
material of the central AGB star preferentially on the equatorial
plane, and a superwind shell with a torus-like density
enhancement develops deep within the spherically symmetric
AGB wind shell. The equatorial density enhancement
in the superwind shell is further strengthened as the
star evolves.
,______ _ _ ____ __ _ __ ____ -./ ___ ______ ___ ______)_ _
_____ __ ' __ __
___' (__ _
__
Huarte-Espinosaet al 2012: for PN:
10,000 yr simulation
AGB wind 10 km/s 10-5 M/yr 500K
Jet, 200 km/s 500K 5 10-6 m/yr for just 100years
After jet is turned off:
Fast wind starts. 5 -10-7 down to 5 10-9 over 10,000 yr
Speed increases from 200 to 2000
rho v2 = constant (ram pressure is const)
Identifying PN:
http://adsabs.harvard.edu/abs/2014apn6.confE..98S
PROJECT 141030
The three recent papers described belowmay provide the keys to understand
the chemistry during the transition from AGB to PN. Can we reconstruct what is
happening with these shell/rings? How many ejections are there really? Can we
measure them off images?
Elements C N and O are enhanced. But not sure how we can approach
chemistry systematically, especially when it is so dependent on precise
evolutionary stage. Fascinating papers –use arXiv e-print link on the
following pages to get the pdf files even when not at the Uni.
http://adsabs.harvard.edu/abs/2013ApJ...773...71Z
Through comparisons of molecular line strengths in asymptotic giant branch
stars, PPNs, and planetary nebulae, we discuss the evolution in circumstellar
chemistry in the late stages of evolution.
First paragraph of Introduction is excellent!
Stage AGB: CSE rich molecular chemistry
in the AGB stage have simi- lar chemical compositions
Stage PPN: just 1000 yr ? chemistry?
Different carbon-to-oxygen abundance ratio sets up different reaction routes.
Stage Pn: molecules dissociated, atoms ionised
In the PN stage, the chemical composition changes dramatically
They study a PPN: AFGL 2688, with the goal of investigating the chemical
transition in the short evolutionary timescale between the AGB and PN stages.
This is interesting because shock-chemistry – collisional-triggered chemistry
after heating from a shock wave – should be dominant.
http://adsabs.harvard.edu/abs/2012ApJ...745..188B
(a) We present four-color images of CRL 2688 (Same object!)
(b) The rings were ejected every 100 yr for ~4 millennia until the lobes formed
250 yr ago.
© the rings were ejected at ~18 km s-1 with very little variation
the mass and momentum of the AGB winds and their rings have increased over
time.
http://adsabs.harvard.edu/abs/2012MNRAS.425..997I
Yttrium is also enhanced (wonderful ‘pointless’ element)
Analysis of the molecular features, presumably originating from circumstellar
matter, provides further constraints on the chemistry and velocity of the
expanding shell, expelled as a consequence of the strong mass loss
experienced by the central star.
http://adsabs.harvard.edu/abs/2014apn6.confE..18D
There is no quantitative theory to explain why a high 80% of all planetary
nebulae are non-spherical. The Binary Hypothesis states that a companion to
the progenitor of a central star of planetary nebula is required to shape nebulae
whose shapes are not spherical or mildly elliptical, implying that many single
post-AGB stars do not make a PN at all. A way to test this hypothesis is to
estimate the binary fraction of central stars of planetary nebula and to compare
it with that of the main sequence population. Preliminary results from the
infrared excess technique indicate that the binary fraction of central stars of
planetary nebula is higher than that of the main sequence, implying that PNe
could preferentially form via a binary channel. I will present new results from a
search of red and infrared flux excess in an extended sample of central stars of
planetary nebula and compare the improved estimate of the PN binary fraction
with that of main sequence stars.
REVIEW
http://adsabs.harvard.edu/abs/2012IAUS..283..180S
http://adsabs.harvard.edu/abs/2014apn6.confE..39H
http://adsabs.harvard.edu/abs/2014A%26A...567A..12G
REVIEW:
http://adsabs.harvard.edu/abs/2014apn6.confE..87S
OPACOS: OVRO Post-AGB CO (1-0) Emission Survey. I. Data and Derived
Nebular Parameters
http://adsabs.harvard.edu/abs/2012ApJS..203...16S
http://www.astro.keele.ac.uk/AGBnews/view.html
Millar:
http://adsabs.harvard.edu/abs/2005ESASP.577..229M