SPIRE-NEP
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# SPIRE-NEP: Validation Report (FULL)

SPIRE-NEP: Validation Report (FULL)¶

and extended objects.__
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Master catalogue used: __master_catalogue_spire-nep_20171122.fits__<br>Number of rows: 2,674<br>Surveys included:<br>​| Survey     | Telescope / Instrument      |      Filters (detection band in bold)      | Location                    ||------------|-----------------------------|:------------------------------------------:|-----------------------------|| PS1 3PSS   | Pan-STARRS1                 | grizy                                      | dmu0_PanSTARRS1-3SS         |​​__NB: On the SPIRE-NEP field, only PanSTARRS observations are available. We can then compared with other surveys to find outliers or look at the difference in aperture correction between point-source and extended objects.__

Master catalogue used: master_catalogue_spire-nep_20171122.fits
Number of rows: 2,674
Surveys included:

Survey	Telescope / Instrument	Filters (detection band in bold)	Location
PS1 3PSS	Pan-STARRS1	grizy	dmu0_PanSTARRS1-3SS

NB: On the SPIRE-NEP field, only PanSTARRS observations are available. We can then compared with other surveys to find outliers or look at the difference in aperture correction between point-source and extended objects.

## I. Caveats

I. Caveats¶

### I.a. Magnitude errors

I.a. Magnitude errors¶

ELAIS-N2_magVSmagerr_Megacam_u_mag_total.png
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At faint magnitudes (mag > 24), few __PanSTARRS__ sources have very large errors on their __aperture and total __magnitudes. These objects may be unreliable for science puposes.<br>​​<img src="help_plots/SPIRE-NEP_magVSmagerr_GPC1_g_mag_total.png" />​

At faint magnitudes (mag > 24), few PanSTARRS sources have very large errors on their aperture and total magnitudes. These objects may be unreliable for science puposes.

SPIRE-NEP
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### I.b. Aperture corrections​On SPIRE-NEP there are no sources with multiple aperture magnitudes. We then cannot look for difference in aperture correction between point-source and extended objects for different surveys.

I.b. Aperture corrections¶

On SPIRE-NEP there are no sources with multiple aperture magnitudes. We then cannot look for difference in aperture correction between point-source and extended objects for different surveys.

## II. Flags

II. Flags¶

ELAIS-N2_gpc1Issues_GPC1_g_mag_aperture.png
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### II.a. Pan-STARRS aperture magnitude​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/SPIRE-NEP_gpc1Issues_GPC1_g_mag_aperture.png" />

II.a. Pan-STARRS aperture magnitude¶

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.

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/ELAIS-N2_outliers_Megacam_g_total_-_GPC1_g_total.png"/>
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### II.c. Outliers​There are no bands with multiple observations, we then cannot flag outliers in this field.

II.c. Outliers¶

There are no bands with multiple observations, we then cannot flag outliers in this field.

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