Beta Peg
For the range in background values, see
2MASS Confusion Noise
Halo/spike Masking Radius
northern hemisphere
JHK mag vs. masking radius, low backgrounds
JHK mag vs. masking radius, mid backgrounds
JHK mag vs. masking radius, high backgrounds
white = halo radius, green = spike radius, red = linear fit
southern hemisphere
JHK mag vs. masking radius, low backgrounds
JHK mag vs. masking radius, mid backgrounds
JHK mag vs. masking radius, high backgrounds
white = halo radius, green = spike radius, red = linear fit
Halo Masking Radius vs. Density
Jmag vs. Density, low background, south
Jmag vs. Density, low background, north
Jmag vs. Density, low background, north&south, w/different solution
Hmag vs. Density, low backgrounds, south
Hmag vs. Density, low backgrounds, north&south
Kmag vs. Density, low backgrounds, south
Kmag vs. Density, low backgrounds, north&south
different colors represent separate mag bins, with the bright
mags demarked with dashed white lines
orange = fit
Fit equation:
J only:
alpha = 0.165
zoff = -0.75
term = (density-zoff*alpha) ** 7
ratio = (exp (-term) / exp(-t0) )
term = (density*alpha) ** 7
t0 = (2.5-zoff * alpha ) ** 10
H and K, only
alpha = 0.21
term = (density*alpha) ** 10
t0 = (2.5 * alpha ) ** 10
ratio = (exp (-term) / exp(-t0) )
For H, add 0.05 to the density,
For K, add 0.25 to the density
Stripes
Horizontal stripes are more difficult to
predict. We can use results from my old analysis
on striping. See for example
Automated Bright Star Masking
Horizontal Stripe SNR & Rating
This plot shows both the measured SNR for primary (white filled points) and secondary
(blue triangles) stripes. A quadratic has been fit to the points. Shown in green (dashed
lines) are the horizontal stripe "rating" determined independently of the SNR business.
A high rating means that the stripe should be blanked, a low rating means it should not
be blanked. Notice that the SNR and the rating are correlated. It appears that an SNR
limit of 2-sigma corresponds to the point where the rating falls off sharply. Thus a limit
of 1 or 2-sigma should be applied to the data (stripes).
For low backgrounds, we see primary striping for stars
brighter than K=6.5 (J=7.5), corresponding to a halo length
of 40 arcsec. For secondary striping, the thrshold is closer
to 4th mag at K, corresponding to a halo radius of 70 arcsec.
Hence, after correction for confusion noise effects, we can look at
the halo radius to predict the presence of hori stripes.
UPDATE: Masking for R1-Saturated Stars
The previous analysis relied upon PIPELINE V2 photometry for bright stars.
Very bright stars that saturate in R1 will not have reliable mags
(nor by association, masking radii) for V2 reduction. The improved
PIPELINE V3 estimates the integrated flux of R1-saturated stars by
integrating and extrapolating the radial profile. Very bright stars
will have reliable mags under most conditions. Analysis of the bright star
masking for these types of stars reveals underestimation of the halo radius.
A slight scaling adjust is therefore made for the bright end of the halo-radius masking
scale.
- Adjust J Halo Masking Radius
Where the faint end (J > 5th mag) follows the masking radius
relation defined above, and the bright end (J < 5th mag) follows
the power law:
Radius = A * 10^(B * mag)
where A and B are constant coefficients, fit to the
faint end and at mag = 0.0.
The same power law is used for the spike length adjustment.
-
Example of a R-1 saturated star, Jmag = 2nd mag,
shown with the masking radii, including halo, spike, stripes, glints and persistence.
