Download How the quasars (lower right) are different than brown dwarfs

Astrometry
Check that the
image is correct
from the point
of view of
astrometry.
It is assumed
that you know
the rough centre,
orientation and
image scale.
Check that the
image is correct
from the point
of view of
astrometry.
It is assumed
that you know
the rough centre,
orientation and
image scale.
The next stage is
to get some
reference
positions from an
on-line
catalogue.
Check that the
image is correct
from the point
of view of
astrometry.
You should get a list of
positions that are
displayed as circles with
interior crosses over your
image.
Check that the
image is correct
from the point
of view of
astrometry.
You should get a list of
positions that are
displayed as circles with
interior crosses over your
image.
If you're good or lucky then
you should be able to spot
the pattern between the
catalog positions and your
image.
Check that the
image is correct
from the point
of view of
astrometry.
You should get a list of
positions that are
displayed as circles with
interior crosses over your
image.
If you're good or lucky then
you should be able to spot
the pattern between the
catalog positions and your
image.
The next stage is to use
these positions to fit a
proper solution: drag the
magenta circles in the right
positions.
Light curves
How is a specific source discovered?
(TDE, SN, etc)
Spectral energy distributions
(SEDs)
Spectrum and spectral energy distribution
Spectral energy
distributions for typical
galaxies - an old
elliptical galaxy, two
types of spiral galaxies
(Sb in green and Sd), an
AGN (Markarian 231,
solid black), a QSO
(dotted black), and a
merging and starbursting galaxy Arp 220.
For a starbursting galaxy
that is undergoing a
merging event, such as
Arp 220 (purple line), the
SED shows that the
galaxy is very bright in the
infrared compared to its
optical emission and
compared to normal starforming galaxies like the
two spiral galaxies. That is
why Arp 220 belongs to
the class of ultra-luminous
infrared galaxies.
AGN on the other hand
show themselves in the
ultraviolet, optical, X-ray,
and sometimes also at
radio wavelengths.
The overall shape of an
AGN SED (shown here is
that of Mrk 231) is similar
to that of a power law,
meaning the black line is
very flat at optical and IR
wavelengths.
The SED of a QSO, a
quasi stellar object, an
object for which the AGN
outshines the host galaxy
in which it resides, is very
steep and shows emission
lines in the UV and optical.
If dust is present in a
galaxy then some of the
ultraviolet and blue optical
light is absorbed and reemitted in the infrared
which can be seen as
bumps in the purple, blue
and green curves (around
a wavelength of 5 to 110
micron).
You might have also
noticed the "spikes" of
emission in the SEDs
around about 5 to 12
micron, these are caused
by so-called polycyclic
aromatic hydrocarbons
(PAHs), which are a class
of organic molecules.
They give important clues
towards the structures of
dust in galaxies, star
formation, and the merger
histories of galaxies.
Emitting sources and emission processes at different wavelengths
Diagrams
There is a relationship between the luminosity
& surface temperature based upon:
- the initial mass of a star
- its age
- its composition (usually a small effect)
H-R diagram (L-T)
H-R diagram (L-Spectral classes)
To first order, the light emitted
by a star is a black body.
Thus, rather than actually
measure & plot (in Kelvin) the
temperature of every star, it is
MUCH easier and quicker to
simply measure & plot the ratio
of the intensity of the star in
two spectral bands. This ratio
is then directly related to the
black body function and hence
temperature.
For primarily historical reasons,
the ratio is usually expressed
as the difference (in
magnitudes) between two
standard (optical/IR) spectral
bands and is known as the
color. Traditionally, the most
commonly used color is the
difference between the B and V
bands (centered at 440 & 550
nm, respectively) and usually
written as simply B – V.
Similarly, rather than actually
measure & plot (in W/m^2)
the total flux of every star, it
is MUCH easier to simply
measure & plot the flux in a
standard spectral band.
Again since the emitted
spectra are black bodies, this
is directly related to the total
flux.
Traditionally, the most
commonly used band is the V
band (550 nm) and usually
written as simply V.
Hence, typically CM diagrams
are used rather than HR
diagrams. For example
- if the distances to all the
stars have been determined,
then this might be a plot of B -V
versus absolute V band
magnitude.
- if the distances to all the
stars have NOT been
determined (say for a star
cluster), then this might be a
plot of B - V versus apparent V
band magnitude.
These are both equivalent to
plots of luminosity vs.
temperature.
In order to compare CM diagrams of two different clusters at two different
distances, you need to know the distance to each cluster in order to
calculate the absolute magnitude from the apparent magnitude.
In order to compare CM diagrams of two different clusters at two different
distances, you need to know the distance to each cluster in order to
calculate the absolute magnitude from the apparent magnitude.
But what if you don't know the distances to the clusters?
Wouldn't it be nice to still be able to learn something about the clusters,
even if you don't know the distances?
The magnitude of a star is related to the log of the flux.
Therefore, a color (or the difference of two magnitudes) is related to the
ratio of the fluxes. When you take the ratio of the fluxes of the same star,
the distance cancels out.
The magnitude of a star is related to the log of the flux.
Therefore, a color (or the difference of two magnitudes) is related to the
ratio of the fluxes. When you take the ratio of the fluxes of the same star,
the distance cancels out.
The point is that colors are independent of distances!
So a color-color plot is also independent of distance.
The magnitude of a star is related to the log of the flux.
Therefore, a color (or the difference of two magnitudes) is related to the
ratio of the fluxes. When you take the ratio of the fluxes of the same star,
the distance cancels out.
The point is that colors are independent of distances!
So a color-color plot is also independent of distance.
Example: by studying main-sequence clusters, we can determine the
locations of "normal" stars (or other objects) in nearly any color-color
space. Then, stars (or other objects) that have colors different than these
normal objects stand out.
The relationship between two colors (U-V
and V-I) for normal stars is indicated by the
line marked "ZAMS Relation." Normal stars
are clumped along this line.
Stars significantly above this line are
brighter than expected in U-V given their
observed color in V-I.
Color-color plots can be used to
separate objects of different types,
such as distinguishing galaxies
from stars.
i*-z* and z*-J
color-color
diagram
How the quasars
(lower right) are
different than brown
dwarfs (top) and
more boring objects
(cluster of points).
T dwarf
L dwarf
Quasar
BAL quasar
http://iopscience.iop.org/article/10.1086/324111/pdf
i*-z* and z*-J
color-color
diagram
How the quasars
(lower right) are
different than brown
dwarfs (top) and
more boring objects
(cluster of points).
T dwarf
L dwarf
Quasar
BAL quasar
http://iopscience.iop.org/article/10.1086/324111/pdf
i*-z* and z*-J
color-color
diagram
How the quasars
(lower right) are
different than brown
dwarfs (top) and
more boring objects
(cluster of points).
T dwarf
L dwarf
Quasar
BAL quasar
http://iopscience.iop.org/article/10.1086/324111/pdf
i*-z* and z*-J
color-color
diagram
How the quasars
(lower right) are
different than brown
dwarfs (top) and
more boring objects
(cluster of points).
T dwarf
L dwarf
Quasar
BAL quasar
http://iopscience.iop.org/article/10.1086/324111/pdf
SDSS
The Sloan Digital Sky Survey has created
the most detailed three-dimensional maps of
the Universe ever made, with deep multicolor images of one third of the sky, and
spectra for more than three million
astronomical objects.
eBOSS (Extended Baryon Oscillation
Spectroscopic Survey) will map the
distribution of galaxies and quasars from
when the Universe was 3 to 8 billion years
old, a critical time when dark energy
started to affect the expansion of the
Universe.
eBOSS concentrates its efforts on the
observation of galaxies and in particular
quasars, in a range of distances (redshifts)
currently left completely unexplored by
other three-dimensional maps of largescale structure in the Universe. In filling
this gap, eBOSS will create the largest
volume survey of the Universe to date.
SDSS: camera and filters
The Sloan Digital Sky Survey has created
the most detailed three-dimensional maps of
the Universe ever made, with deep multicolor images of one third of the sky, and
spectra for more than three million
astronomical objects.
SDSS camera
The imaging camera collects photometric
imaging data using an array of 30
SITe/Tektronix 2048 by 2048 pixel CCDs
arranged in six columns of five CCDs each,
aligned with the pixel columns of the CCDs
themselves. SDSS r, i, u, z, and g filters cover
the respective rows of the array, in that order.