Towards a complete census of
planetary nebulae, symbiotic stars
and related systems
in the Milky Way
Romano L. M. Corradi
Instituto de Astrofísica de Canarias
and the IPHAS collaboration
(L. Sabin, K. Viironen, E.R. Rodríguez-Flores, C. Giammanco, L. Ramirez, ...
A. Mampaso, Q. Parker, A. Zijlstra, M. Barlow, R. Morris, J. Drew, ...
D. Jones ...)
Planetary nebulae (PNe) as a stellar population
“Semi-final” stage of stellar evolution for the majority of stars in the
Universe (1 to 8 MΘ)
+
well-known atomic physics
+
characteristic spectrum detectable up to large distances (100 Mpc)
+
found in any stellar system
=
Excellent tracers of luminosity, distance, dynamics, and chemistry
of stellar populations in any galaxy
R. Corradi, "Milky Way Astrophysics from Wide-Field Surveys" London 31-3-20152
Luminosity tracers
Renzini & Buzzoni 1986, ApSpScLib 122,
p.195
Buzzoni, Arnaboldi & Corradi 2006, MNRAS
368, 877
NPN / Ltot = B x t
B = specific evolutionary flux
t = PN lifetime
Distance tracers
The Planetary Nebula Luminosity Function (PNLF) in the [O III]5007 nebular line has a
universal bright cutoff
at M[OIII] = -4.53 (600 LSUN!), with small metallicity dependence
Ciardullo et al. 1989 ApJ 339, 53
Crucial link between Pop I and II distance scales
M31
But...
The lower and upper limit of stars forming PNe are not well determined.
The question was raised on whether binary stars produce the majority of observed PNe, as:
- 2700 Galactic PNe known before IPHAS, estimated population 30000-50000: observed
Galactic PN population 1/5 of predicted by population synthesis models
Moe & De Marco 2006 ApJ 650, 916; Moe & de Marco 2012, IAU Symp 283, p. 111
- PN formation rate in the Galaxy is one third of the white dwarf formation rate
Soker 2006 ApJ 645, L57
Most recent estimates of binary fraction ~50-70%
Douchin et al. 2015, MNRAS, 448, 3132
There is no astrophysical explanation of the invariance of the PNLF cutoff. Theory requires
central stars masses >= 2 MSUN, but the number of these stars is too scarce to populate the
PNLF cutoff in old stellar systems. Binary evolution?
Ciardullo et al. 2005, ApJ, 629, 499
Soker 2006, ApJ, 645, L57
As the detailed study of PNe and their central stars in external galaxies is limited by the large
distances, investigation of the above issues requires a comprehensive census in our own
galaxy, and a good determination of distances (GAIA; Barlow this meeting).
R. Corradi, "Milky Way Astrophysics from Wide-Field Surveys" London 31-3-20155
The IPHAS (and VPHAS+) surveys
Systematic effort to make a complete SB-limited census of PNe in the Galactic Plane.
The survey characteristics largely improves the census of :
- compact (young) PNe
Viironen et al. 2009 A&A 502, 113; 504, 291
- extended faint (old) PNe (with ISM interaction)
Wareing et al. 2006 MNRAS 366, 387
- rare classes (e.g. post-CE PNe)
talk of David Jones
- or in specific Galactic regions (e.g. Anticentre for Galactic chemical gradients)
Viironen et al. 2011 A&A 530, 107,Galera et al. 2015 in preparation
Method: Automatic detection for compact sources in the IPHAS photometric catalogue +
(heroic) visual detection in binned mosaics. Spectroscopic follow-up confirmation required.
Results: ~500 PN candidates identified. A first release contains of 159 objects classified as
True (T, 113), Likely (L, 26) and Possible (P, 20) PNe
Sabin et al ,2014, MNRAS,443,3388
The search continues...
R. Corradi, "Milky Way Astrophysics from Wide-Field Surveys" London 31-3-20156
Examples
Sabin et al ,2014, MNRAS,443,3388
Examples: ISM interaction
Wareing et al 2006MNRAS 366, 387
Examples: compact/young
Ha
r
i
Viironen et al. 2009 A&A 502, 113; 504, 291
The Macquarie University GPNe database
Symbiotic stars
They are the interacting binary stars with the longest orbital periods.
Hot WD + a red giant (usually of M-type)
Red giant’s wind is partly ionized by WD -> ionized nebular core
WD accretes matter from the red giant’s wind
Mass accretion near steady-state hydrogen burning -> high luminosity -> (recurrent)
thermonuclear nova-like runaways -> ejecta (fast winds, jets, nebulae)
One of favourite channels to produce SNe Ia (“single-degenerate” scenario). Recurrent
(symbiotic) novae (e.g. RS Oph) provide most promising candidates.
Crucial test is the total population of symbiotic stars and their Galactic distribution
(population age). Estimated between 3000 and 400000
Munari & Renzini 1992 ApJ 397, L87
Before IPHAS, 173 symbiotic stars known, and only 11 in the IPHAS area.
IPHAS discovered another 19
Rodriguez-Flores et al. 2014, A&A 567, A49
New IPHAS symbiotic stars
S (RGB)
D (AGB)
Binary interactions: how nearby?
The Case of Mira. Porb~1000 yrs -> separation of ≥100 AUs, where mass transfer of its
wind onto a white dwarf companion (Mira B) is clearly visible.
IPHAS (VPHAS+) search
A combination of optical
(IPHAS) and NIR (2MASS)
colours has been used for
selection.
Additional constraints from IR
colours (WISE) are being
implemented.
Follow-up
spectroscopy
confirmation.
for
For VPHAS+, cross correlation
with VVV (variability) would
provide additional constraints
(but symbiotics hit the VVV
saturation limits).
E. Rodríguez-Flores 2012 PhD Thesis
IPHAS colour-colour diagram
Corradi et al. 2008,2010
CTT/YSO
Corradi et al. 2008, 2010
2MASS colour-colour diagram
T
CT
O
S
/Y
An additional “new” tool: IR colours (WISE)
Mampaso et al. in preparation
Galactic distribution
T CrB
S
TX CVn
87% in bulge
S-types in bulge, and in disc at large(r) heights
D-types younger disc population with lower scale height
D
R Aqr
Total population
No new S-type symbiotic
stars outside solar circle,
and very few promising
candidates left.
Galactic
Centre
Extrapolating to the whole
disc -> S-type total disc
population < 104
Considering
the
solar
neighborhood (Munari &
Renzini predict 400 within
1kpc)
->
S+D
disc
population <2 104
Perspective:
VPHAS+ should discover
many
symbiotics
in
bulge
Caution:
low number statistics for
extrapolation
10 kpc
Sun
14 kpc
Conclusions
•
19 new symbiotic stars from IPHAS survey. Some specially interesting
systems which deserve further study
•
•
Total number of symbiotic stars expected in the IPHAS area is only a few tens
Most systems in the inner galaxy, possibly belonging to the bulge population
We confirm that S-types seem to belong to a bulge population + disc
population with large(r) scale height than D-types
Paucity of systems outside solar circle -> small disc population (<104 for Stypes, perhaps 103)
VPHAS will provide strong constraints to Galactic distribution and
determination of both disc and bulge populations.
Besides counts, distances are the other essential ingredient: GAIA, extinction
distances (complicated by internal dust), precise calibration of absolute
magnitude of symbiotic red giants.
Caveat: with present search methods, only symbiotic stars with bright
emission lines confirmed as such. Symbiotic with low or zero level activity
missed.
•
•
•
•
•
How many symbiotic stars in the Galaxy?
Munari
Corradi
Gabriel García-Marquez “The general in his labyrinth”