# AKARI-NEP: Validation Report (FULL)

AKARI-NEP: Validation Report (FULL)¶

master_catalogue_akari-nep_20171211.fits
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Master catalogue used: __master_catalogue_akari-nep_20180205.fits__<br>Number of rows: 531,746<br>Surveys included:<br>​​| Survey | Telescope / Instrument  | Filters (detection band in bold)  | Location        ||--------|-------------------------|:---------------------------------:|-----------------|| AKARI-NEP-OptNIR | CFHT/Megacam/WIRCAM | u*g'r'i'z'YJK        | dmu0_AKARI-NEP-OptNIR |  | PanSTARRS-3SS | GPC1             | grizy                          | dmu0_PanSTARRS-3SS |     | NEP-Spitzer | Spitzer/IRAC             |  IRAC12                    | dmu0_NEP-Spitzer | ​__NB: Megacam and WIRCAM do not have aperture magnitudes for AKARI-NEP__

Master catalogue used: master_catalogue_akari-nep_20180205.fits
Number of rows: 531,746
Surveys included:

Survey	Telescope / Instrument	Filters (detection band in bold)	Location
AKARI-NEP-OptNIR	CFHT/Megacam/WIRCAM	u*g'r'i'z'YJK	dmu0_AKARI-NEP-OptNIR
PanSTARRS-3SS	GPC1	grizy	dmu0_PanSTARRS-3SS
NEP-Spitzer	Spitzer/IRAC	IRAC12	dmu0_NEP-Spitzer

NB: Megacam and WIRCAM do not have aperture magnitudes for AKARI-NEP

## I. Caveats

I. Caveats¶

### I.a. Magnitude errors

I.a. Magnitude errors¶

 
At faint magnitudes (mag > 24), some surveys have very large errors on the magnitude. These objects may be unreliable for science puposes.<br>This includes __PAn-STARRS aperture and total__ (at mag > 23). <br>​​<img src="help_plots/AKARI-NEP_magVSmagerr_GPC1_g_mag_total.png" />​

At faint magnitudes (mag > 24), some surveys have very large errors on the magnitude. These objects may be unreliable for science puposes.
This includes PAn-STARRS aperture and total (at mag > 23).

## II. Flags

II. Flags¶

 
### II.a. Pan-STARRS aperture and total magnitudes​Few Pan-STARRS sources have exactly the same error (of <font color='blue'>0.0010860000038519502</font>) on the __aperture and total__ magnitudes in all the grizy bands. The corresponding aperture magnitude should not be trusted for these objects.<br>​<img src="help_plots/AKARI-NEP_gpc1Issues_GPC1_i_mag_aperture.png" />

II.a. Pan-STARRS aperture and total magnitudes¶

Few Pan-STARRS sources have exactly the same error (of 0.0010860000038519502) on the aperture and total magnitudes in all the grizy bands. The corresponding aperture magnitude should not be trusted for these objects.

 
### II.c IRAC aperture magnitude​IRAC1 and IRAC2 bands are available in this field, but there are __no__ sources with exactly the same magnitude (as it is the case in other fields with IRAC observations).

II.c IRAC aperture magnitude¶

IRAC1 and IRAC2 bands are available in this field, but there are no sources with exactly the same magnitude (as it is the case in other fields with IRAC observations).

 
### II.b. Outliers​By comparing magnitude in the same band between different surveys, we can see that some magnitudes are significanlty different could not be trusted. <br>The outliers are identified to have a large weighted magnitude difference (equivalent of the $chi^2$).​$$chi^2 = \frac{(mag_{1}-mag_{2})^2}{magerr_{1}^2 + magerr_{2}^2}$$ <br>We used the 75th and 25th percentile to flagged the objects 5$\sigma$ away on the large values tail of the $chi^2$ ditribution. (__NB:__ bright sources tend to have their errors underestimated with values as low as $10^{-6}$, which is unrealistic. So to avoid high $chi^2$ due to unrealistic small errors, we clip the error to get a minimum value of 0.1% (i.e. all errors smaller then $10^{-3}$ are set to $10^{-3}$).)<br><br>$$outliers == [chi^2 >  (75th \;percentile + 3.2\times (75th \;percentile - 25th \;percentile))]$$​<img src="help_plots/AKARI-NEP_outliers_Megacam_r_total_-_GPC1_r_total.png"/>

II.b. Outliers¶

By comparing magnitude in the same band between different surveys, we can see that some magnitudes are significanlty different could not be trusted.
The outliers are identified to have a large weighted magnitude difference (equivalent of the $chi^2$ ).

c h i^{2} = \frac{(m a g_{1} - m a g_{2})^{2}}{m a g e r r_{1}^{2} + m a g e r r_{2}^{2}}

$chi^2 = \frac{(mag_{1}-mag_{2})^2}{magerr_{1}^2 + magerr_{2}^2}$
We used the 75th and 25th percentile to flagged the objects 5

σ

$\sigma$ away on the large values tail of the

c h i^{2}

$chi^2$ ditribution. (NB: bright sources tend to have their errors underestimated with values as low as

10^{- 6}

$10^{-6}$ , which is unrealistic. So to avoid high

c h i^{2}

$chi^2$ due to unrealistic small errors, we clip the error to get a minimum value of 0.1% (i.e. all errors smaller then

10^{- 3}

$10^{-3}$ are set to

10^{- 3}

$10^{-3}$ ).)

o u t l i e r s == [c h i^{2} > (75 t h p e r c e n t i l e + 3.2 \times (75 t h p e r c e n t i l e - 25 t h p e r c e n t i l e))]

$outliers == [chi^2 > (75th \;percentile + 3.2\times (75th \;percentile - 25th \;percentile))]$

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