Transcript M77 (NGC 1068)

M77 (NGC 1068)
By: Ryan Desautels
Messier 77
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A Brief History
General Information
Galactic Information
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Research Question
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AGN
Seyfert
Does M77 have a
barred structure?
Does the brightness
change, is it possible to
detect this change?
Summary
A Brief History
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October 29th, 1780;
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First observation made of NGC 1068 by M. Mechain.
He described it as a nebula
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December 17th, 1780;
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Observed by Charles Messier and catalogued as
“Cluster of faint stars, which contains nebulosity…” (Charles
Messier, Catalogue).
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http://www.seds.org/messier/m/m077.html
http://www.kopernik.org/images/archive/m77.htm
Other notable early observations;
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W. Hershel described M77 as a cluster of stars.
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http://www.kopernik.org/images/archive/m77.htm
Rosse was the first astronomer to recognize M77 as a galaxy
and not a star cluster.
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http://www.kopernik.org/images/archive/m77.htm
General Information
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Type
 What
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Size
 What
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type of galaxy is Messier 77?
are some of the dimensions of Messier 77?
Brightness
 What
is the brightness of Messier 77 and some of
its oddities?
Type
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NGC 1068 is a spiral galaxy (barred?).
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Type Sb using Hubble’s Tuning Fork Diagram.
 I will give an argument why this classification is no
longer accurate.
Part of a group of galaxies known as
Seyfert Galaxies.
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Seyfert Galaxies are a subset of galaxies and other
objects known as Active Galactic Nuclei (AGN).
M77 is the prototype galaxy for the Seyfert class.
Bar or no bar?
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Well, according to
Gilbert A.
Esquerdo and
John C. Barentine,
there is a barred
structure present,
at least in IR
wavelengths.
W
N
Bar in optical?
Size
M77 is slightly larger then our own Milky
Way.
 M77 has an extent of roughly 170 000 light
years with a core (brightest area) that
makes up about 71% of it’s total size
(120 000 light years).
 It is at a distance of approximately 60
million light years.
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Size
120 000ly
Brightness
Messier 77 has a brightness that varies
(most observatories and papers classify
the brightness somewhere in the range of
8.9 to 10.5).
 Brightness variations is a property of
Seyfert galaxies. Not only do they vary in
brightness, they can also vary in class.
 Messier 77 has a period of less then a
week.
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Brightness
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The core of M77 is very similar to that of a
star (point source). Which is a property of
Seyfert Galaxies.
Active Galactic Nuclei (AGN)
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A little background information on AGN’s
What are AGN’s
 Are there different types of AGN’s, if so, what
are they
 Basic properties of AGN’s
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What are AGN’s
As a group, they are the most active
galaxies out there.
 Galaxies who’s nuclei alone produce more
radiation then the rest of the galaxy.
 The widely accepted model of an AGN
galaxy is that it has a central super
massive black hole as it’s engine.
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Different types of AGN’s
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AGN’s are a general class of galaxies
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Seyfert Galaxies
 Type
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1, and 2
Radio Galaxies
 Radio
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Quasars
 Very
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luminosity > 1033 W
distant AGN’s
BL Lacertae Objects
Basic properties of AGN’s
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AGN’s as a group show all or most of the
following characteristics.
High luminosity greater then 1037 W.
 Nonthermal emission, with excessive UV, IR,
Radio and X-Ray flux (compared to most
galaxies).
 Small region of rapid variability.
 High contrast of brightness between nucleus
and other structures (large scale).
 Broad emission lines (sometimes).
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Seyfert Galaxies
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First discovered by Carl K. Seyfert.
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Messier 77 is the prototype Seyfert Galaxy.
What are Seyfert Galaxies?
 What are the different types?
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Type: 1,1.5,2
What do different Seyfert galaxies share in
common.
 How is M77 a Seyfert Galaxy.
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Carl K. Seyfert
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Pioneered research on nuclear emission in
spiral galaxies.
1943 he published a paper on galaxies with
bright nuclei that exhibit characteristically
broadened emission lines.
While at Warner Swasey Observatory and the
Case Institute, he obtained the first good colour
photographs of nebulae and stellar spectra.
Involved in instrumental innovations which
included the use of photomultiplier tubes and
television techniques in astronomy, and
electronically controlled telescope drives.
Different Types of Seyfert Galaxies
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There are two different types of Seyfert
Galaxies.
NGC 5548
Type 1
M77
Type 2
Type 1
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Type 1 galaxies have two sets of emission
lines in their spectra:
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Narrow lines, with widths of several hundred km/s
Broad lines, with widths of up to 104 km/s
Type 2
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Object has only narrow lines present.
Why different types
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Types 1 and 2 are only different because
of our point of view. It is thought that the
differences are due to a torus which is
preventing us from seeing the broad
regions in Seyfert 2 galaxies.
Messier 77’s variability
Is it possible to detect the variability?
 If it is possible, what is the range in
apparent magnitude?
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Variability
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To find the variability:
 Measure
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each individual object image.
Set the mean value of each object image ~ 0
 Measure
the FWHM of a non-variable star in the
field.
 Measure an area around the star .
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~ 4x FWHM.
 Adjust
each image so that the star brightness
(mean value) is the same in each object image.
Variability
 Measure
the FWHM of the galaxy.
 Measure an area around the core of the galaxy.
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~ 4x FWHM
 Using
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the formula:
m-n = (2.5)log(Fn/Fm),
 Where m-n = the change in brightness,
 Fn = the mean value of the star,
 Fm = the mean value of the galaxy.
Variability
Variability
Variability
Variability
Variability
Variability
We can see from the previous graph that
there is some variability.
 There is a change in variability of 0.07.
 This change is quite small, however; it is
greater then the error so I can say that
there is definitely a change in brightness.
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Summary
Messier 77 is a Sb Type 2 Seyfert Galaxy.
 It satisfies some of the criterion of the AGN
model.
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Summary
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Small region of rapid variability.
 Yes,
as shown in my graph the brightness does
change, and the period of M77 is roughly 1 week.
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http://www.kopernik.org/images/archive/m77.htm
Summary
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High contrast of brightness between
nucleus and other structures (large scale).
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Yes, it is only with special filters (Digital Development
Processing DDP), that we are able to make out the
central bulge area and the rest of the galaxy.
Summary
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Messier 77 is a galaxy who’s core has an
almost stellar output.
References
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Images:
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http://www.aao.gov.au/images/captions/aatccd012.html
http://archive.stsci.edu/cgi-bin/dss_form?target=m77&resolver=SIMBAD
http://cas.sdss.org/dr3/en/proj/advanced/galaxies/tuningfork.asp
http://www.noao.edu/outreach/aop/observers/m77.html
http://nedwww.ipac.caltech.edu/cgi-bin/nphimgdata?objid=58240&objname=MESSIER%20077
http://www.astrosurf.com/astroduvel/images/m77.html
Information:
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http://imagine.gsfc.nasa.gov/docs/science/know_l1/active_galaxies.html
http://www.astr.ua.edu/keel/agn/
http://www.noao.edu/outreach/aop/observers/m77.html
http://coolcosmos.ipac.caltech.edu/cosmic_classroom/multiwavelength_astronomy/
multiwavelength_museum/m77.html
http://seds.lpl.arizona.edu/messier/more/m077_hst.html
http://www.messiermarathon.com/new_page_83.htm
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Introductory Astronomy & Astrophysics 4th E., 1998
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http://www.ne.jp/asahi/stellar/scenes/object_e/m77.htm
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