NGC 1530
By Cole Treyturik
SECTION 1
Introduction
2
• Name: NGC 1530
• Type: Barred Spiral Galaxy[1]
•
SBb
• Co-Ords:[2]
•
•
•
J2013.04 (January 15th, 2013):
Right Ascension: 4h 25m 5s
Declination: +75º 19' 46”
J2013.13 (February 15th, 2013):
Right Ascension: 4h 25m 5s
Declination: +75º 19' 47”
J2013.20 (March 15th, 2013):
Right Ascension: 4h 25m 6s
Declination: +75º 19' 47”
Introduction
3
• Apparent Magnitude: m=12.00[2]
• Size: 0º 4' 54” [2]
• Angular Size:[1]
•
•
•
Major Axis: 3.287' = 197.2”
Minor Axis: 1.315' = 78.9”
Area (A): 15560.7”2
• Surface Brightness:
•
= 22.5 (mag / ”2)
• Physical Size:[3]
•
•
Major Axis: 36.65 kpc
Minor Axis: 14.66 kpc
Introduction
4
NGC 1530 is located within
the constellation of
Camelopardalis[4]
Image taken using Stellarium
Introduction
5
NGC 1530 is located within
the constellation of
Camelopardalis[4]
Image taken using Stellarium
Introduction
6
Optics
24-inch RC Optical Systems Telescope[5]
Camera
SBIG STL11000 CCD Camera[5]
Filters
Custom Scientific[5]
Dates
November 20th 2009[5]
Location
Mount Lemmon SkyCenter[5]
Introduction
7
Optics
FS-128 (ag, ST-4)[6]
Camera
ST-2000XM LRGB 15 minute subs[6]
Filters
Unknown
Dates
December 2006[6]
Location
Penryn, California[6]
Introduction
8
• Over 100 million light-years away[7]
• One of the largest barred spiral galaxies in the Northern
Hemisphere[7]
• One of the “strongest” bars observable[7]
• Rare double-spiral formation[7]
Introduction
9
SECTION 2
Data + Observations
10
• Observations were made on the night of 28/02/2013 – 01/03/2013
• Conditions for the night were quite good
•
•
•
•
•
•
•
•
•
•
Temperature: -9ºC
Darkness: 4/5
Seeing: 4.5/5
Transparency: 4/5
SQM Readings: 20.12, 20.13, 20.12
Clouds: ~10% cover
Wind: Little-to-none
Humidity: Low
Moon phase: Waning Gibbous, mostly full (did not rise until ~23:00 CST)
Start of Astronomical Twilight: 19:57 CST[8]
Data + Observations
11
Master bias frame from
the night, created using
ImageJ
Data + Observations
12
Master dark frame from
the night, created using
ImageJ
Data + Observations
13
Master flat frame from
the night, created using
ImageJ
Data + Observations
14
Processed image from
the night, created using
ImageJ
Data + Observations
15
Processed image from
the night, created using
ImageJ
Data + Observations
16
Processed image from
the night, created using
ImageJ
Data + Observations
17
• Creation of the final image followed the normal steps, for the most
part:
• Subtraction of the master bias, master dark from the individual images
• Division of the individual images by the master flat
• Around 1/3rd of the frames were significantly brighter than the rest,
likely due to a wandering cloud
• All images were then averaged out to an average pixel value of 900.
• Images were aligned using the “StackReg” plugin
• Images were then cropped, and combined using the “Average
Intensity” setting of Z-Project.
Data + Observations
18
Final, fully processed
image from the night,
created using ImageJ
Data + Observations
19
SECTION 3
Research + Knowledge
20
• Paper: “The Mass Inflow Rate in the Barred Galaxy NGC 1530”
•
Michael W. Regan, Stuart N. Vogel, Peter J. Teuben
• University of Maryland
• Submitted to the Astrophysical Journal Letters on July 17, 1996[9]
•
Accepted on March 31 1997[9]
• Published online on April 1, 1997[10]
• In print June 20, 1997 in Volume 482, Issue 2 of Ap J Letters[9]
• http://arxiv.org/abs/astro-ph/9704009
Research + Knowledge
21
“Mass inflow in barred galaxies has been invoked to account for a wide variety of phenomena, but
until now direct evidence for inflow has been lacking. We present Fabry-Perot H-alpha observations of
the barred spiral galaxy NGC 1530 from which we determine velocities of the ionized gas for the entire
region swept by the bar. We compare the velocity field to models of gas flow in barred spirals and
show that it is well reproduced by ideal gas hydrodynamic models. Inspection of the models and
observations reveals that gas entering the bar dust lanes streams directly down the dust lanes toward
the 2 kpc radius nuclear ring. The models predict that approximately 20% of the gas flowing down the
dust lane enters the nuclear ring; the remaining gas sprays around the ring to the other bar dust lane.
The fraction of the gas entering the ring is relatively insensitive to the shape or size of the bar. Our
observations of the velocity field and dust optical depth yield a mass inflow rate into the nuclear ring
of 1 solar mass per year.”
Research + Knowledge
22
• To summarize the abstract, mass flowing into the centre of barred
galaxies had been used as an explanation for several phenomena,
but without any direct observations
• By comparing models of the velocity of gasses within and without
the bar to observations of such, the rate of gas flow into the centre
can be calculated
Research + Knowledge
23
• What is a “bar?”
• Galaxies come in several different types
• Elliptical, spiral, irregular
• The “spiral” classification contains two subtypes
• Barred and non-barred
• A spiral galaxy is classified as “barred” when its spiral arms sprout
out of a “rectangular” formation rather than the nucleus
• This formation is known as the “bar” of a galaxy
• It is thought that these bars fuel star formation via channeling
gasses inwards
Aside
24
• Because of its highly pronounced bar and the angle it makes to us,
NGC 1530 makes a great target for such observations
• Using Fabry-Perot measurements of the galaxies’ Hα lines, it was
possible for the authors to obtain kinematic values for the galaxy
Research + Knowledge
25
• What is “Fabry-Perot?”
• A Fabry-Perot interferometer (sometimes referred to as an etalon) is
a highly sensitive optical system
• They are commonly used in astronomy as a spectrometer, due to the
fact that they are able to easily view single atomic transition lines – such
as the Hα line
• They use interference to enhance the subtle difference in
wavelengths of detected light
Aside
26
• The observations used for this report were made on the night of
30/09/1994 – 01/10/1994, at the Palomar Observatory
• Telescope used was the 1.5m reflector
• Detector instrument used was the Maryland-Caltech Imaging FabryPerot Interferometer
• Angular resolution for the night ranged from 4” to 15”
Research + Knowledge
27
• The results from comparing the observations to the model were
very favourable - despite the model not being adjusted for the mass
or shape of NGC 1530
• It is found that mass is indeed flowing towards to nucleus, along the
bars, at speeds of between 85 and 200 km/s
• Velocity increases closer to the nuclear ring
• The rate of mass flow was calculated to be 1 (+2 / -0.5) solar masses
per year
Research + Knowledge
28
SECTION 4
Focus Area
29
• Not a widely studied galaxy
• arXiv search for “NGC 1530” returns only 16 results
• Only four of those have the galaxy as their main focus
• Chosen paper focuses primarily on kinematics, which cannot be
measured with our data
• Other topics are touched on, however:
• Axial ratio (ratio of the major axis to the minor axis) of the bar
• Physical size of the bar, nuclear ring
Focus Area
30
• The axial ratio would be rather simple to measure
• In ImageJ, measuring the length of the of the bar vs. the width of the bar
• This, combined with the given nuclear ring radius, could be used to
find the physical size of the galaxy
• This could then be used to find the distance to the galaxy
• Compare the angular size to the obtained physical size
• Axial ratio could also be used to find the incline of the galactic plane
w.r.t. our field of view
• Measure the axial ratio of our images, compare to given ratio in paper
Focus Area
31
•
•
•
•
•
•
•
•
•
•
[1]: Simbad Astronomical Database
[2]: Stellarium: Free Planetarium
[3]: NASA/IPAC Extragalactic Database
[4]: DeepSkyPedia
[5]: University of Arizona’s Mount Lemmon
SkyCenter
[6]: Astrophotos.net
[7]: Mano Prieto Observatory
[8]: US Naval Observatory
[9]: IOP Science
[10]: arXiv.org
References
32