Comparison with Pan-STARRS in the VST Dec<-25 area
Please note that the Pan-STARRS data used here have not been ubercal'd, and the VST data have not been corrected for atmospheric extinction.
r-band magnitude offsets before illumination correction:
 |
After illumination correction:
 |
Stacked VST r-band pointings - before correction:
 |
After correction:
 |
Comparison with APASS in the VST Dec<-25 area
Colour scale spans 0.3 mags. This is APASS-(-2.5*log10(aper_flux_5)-apcor5+zeropt) (illumination corrected). The APASS i-band appears to have problems. VST atmospheric extinction corrections have been applied to g,r & i. Note that APASS is in AB and VST is in Vega.
g-band magnitude offsets: rms scatter is -0.06+/-0.10 (14<g<17)
r-band magnitude offsets: rms scatter is +0.11+/-0.11 (13.5<r<16)
i-band magnitude offsets: rms scatter is +0.34+/-0.15 (12.5<i<15). Obviously the APASS errors contribute.
u-band magnitude offsets: rms scatter is +0.96+/-0.21 (12.5<B<16) actually B_apass - u_vst, empirically corrected by +1.75*(B-V)_apass, as there is a large colour term.
Galaxy counts in the Dec<-25 area
(These are the old zeropoints, i.e. not corrected for atmospheric extinction)
U-band
 |
g_ab
 |
r_ab
 |
i_ab
 |
z_ab
 |
|
Comparison with WHDF
Note the magnitudes are not corrected for colour terms between VST and WHDF, nor for atmospheric extinction.
| Kron | Petrosian |
|---|
| U |  |  |
| U |  |  |
| B |  |  |
| R |  |  |
| I |  |  |
| Z |  |  |
These are WHDF counts of all objects (blue), and those with a match
in the VST catalgoue (red), plotted as a function of WHDF magnitude:
Comparison with Stripe82 around the WHDF area
Comparison with CDFS ESO EIS deep2c data (http://www.eso.org/sci/activities/projects/eis/old_eis/eis_proj/public/summary_dps.html)
Empirical colour equations have been applied, as EIS is in Johnson BRI. No colour equation was used for u'. The x-axis is the colour-corrected EIS magnitude. EIS goes to beyond 24th mag in each band.
| u | g | r | i | z |
|---|
| VST Seeing | 1.1" | 1" | 0.8" | 0.8" | 0.8" |
| VST 5 sigma | 20.68 | 23.15 | 22.43 | 21.75 | 20.19 |
| Bands | Aperture 3 | Aperture 3 EIS stars only | Kron | Petrosian |
|---|
| u(list)/u' |  |  |  |  |
| g/B |  |  |  |  |
| r/R |  |  |  |  |
| i/I |  |  |  |  |
Comparison with MUSYC ECDFS Subaru data (http://www.astro.yale.edu/MUSYC/)
Empirical colour equations have been applied, as MUSYC is in Johnson UBRI (z needs no correction). The x-axis is the colour-corrected Subaru magnitude. Subaru goes to at least 24th mag in each band. See table in previous section for VST image details.
| Bands | Aperture 3 | Aperture 3 MUSYC stars only | Kron | Petrosian |
|---|
| u(list)/U |  |  |  |  |
| g/B |  |  |  |  |
| r/R |  |  |  |  |
| i/I |  |  |  |  |
| z |  |  |  |  |
Comparison with Pan_STARRS MD02 (53,-27.5)
Matched counts (red) cf MD02 count (blue) as a function of PS1 Kron mag:
g-band:
 | r-band:
 |
i-band:
 | z-band:
 |
Comparison with Pan_STARRS PV2 in the North
g-band: ps1-atlas_nightly, stars r<20 (no colour equations used):
r-band: ps1-atlas_nightly, stars r<19.5 (no colour equations used):
i-band: ps1-atlas_nightly, stars i<19:
z-band: ps1-atlas_nightly, stars z<19: (had to apply a 0.1mag offset)
As a check, here is SDSS - Pan-STARRS PV2:
g-band SDSS-PS1
r-band SDSS-PS1
i-band SDSS-PS1
z-band SDSS-PS1
Here is SDSS - APASS:
g-band SDSS-APASS
r-band SDSS-APASS
i-band SDSS-APASS: note the colour scale has changed to span 0.3 mags rather than 0.2
Here is Pan-STARRS PV3.0 - APASS DR9:
g-band PS1-APASS
r-band PS1-APASS
i-band PS1-APASS
Here is Pan-STARRS PV3.0 - 2MASS J:
z-band PS1-2mass J
Here is Pan-STARRS PV3.1 v ATLAS on a tile-by-tile basis (using Mike Irwin's July 2017 catalogues - should contain data for all tiles):
Note: only the latest exposure on each tile is used
| North | South |
|---|
| u-band: ( g-r<0.85: gPS1-uVST = -2.7(g-r)PS1 +0.02 ) ( (g-r)>=0.85: gPS1-uVST = -0.9(g-r)PS1-1.5) TO JULY 2017 |
 |  |
| g-band: (gPS1-gVST = -0.13(g-r)PS1-0.04) TO JULY 2017 |
 |  |
| g-band with abs(nightly-individual)>0.1 replaced with Individual zero-point (data to end of 2015 only): |
 |  |
| r-band: (rPS1-rVST = +0.03(r-i)PS1) TO JULY 2017 |
 |  |
| r-band with abs(nightly-individual)>0.1 replaced with Individual zero-point (PV3.0, data to end of 2015 only): |
 |  |
| i-band: (iPS1-iVST = 0.0PS1) TO JULY 2017 |
 |  |
| i-band with abs(nightly-individual)>0.1 replaced with Individual zero-point (PV3.0, data to end of 2015 only): |
 |  |
| z-band: (zPS1-zVST = +0.055(r-i)+0.10PS1) TO JULY 2017 |
 |  |
Here is Pan-STARRS PV3.1 v ATLAS on a tile-by-tile basis (using Mike Irwin's April 2017 catalogues - should contain all data to the end of 2016) but now with a wider colour scale (+/- 0.1 mag):
| North | South |
|---|
| u-band: (g-r<0.85: gPS1-uVST = -2.7(g-r)PS1-0.02) ((g-r)>=0.85: gPS1-uVST = -1.3(g-r)PS1-1.5) |
 |  |
| g-band: (gPS1-gVST = -0.13(g-r)PS1-0.04) |
 |  |
| r-band: (rPS1-rVST = +0.03(r-i)PS1) |
 |  |
| i-band: (iPS1-iVST = 0.0PS1) |
 |  |
| z-band: (zPS1-zVST = +0.055(r-i)+0.10PS1) |
 |  |
APASS Nightly - APASS individual (using Mike Irwin's April 2017 catalogues - should contain all data to the end of 2016):
| North | South |
|---|
| u-band: |
 |  |
| g-band: |
 |  |
| r-band: |
 |  |
| i-band: |
 |  |
| z-band: |
 |  |
APASS Nightly z-band v 2MASS J (using Mike Irwin's Aug 2016 catalogues):
Two different colour scales. To get the scatter down I have used a restricted z-J range, as a result of which, except for the two single squares, the blank regions are really black (i.e. off scale):
This is all classification=-1 objects with 12.5 < z < 16. The scatter is much worse.
- Now tile by tile [z-H-2*(J-H)+0.5]:
| North | South |
|---|
 |
 |
PS1 V3.0 - Dave Murphy's ubercal with scale of +/-0.05 mags:
| North | South |
|---|
| u-band: |
 |  |
| g-band: |
 |  |
| r-band: |
 |  |
| i-band: |
 |  |
| z-band: |
 |  |
PS1 - Dave Murphy's ubercal with scale of +/- 0.1 mags:
| North | South |
|---|
| u-band: |
 |  |
| g-band: |
 |  |
| r-band: |
 |  |
| i-band: |
 |  |
| z-band: |
 |  |
Skymapper - ATLAS Nightly (to July 2017); scale +/-0.05 except for u
| North | South |
|---|
| u-band: (uSM - uvst +0.1(u-g-1.7)2SM+0.375) ** NOTE THE SCALE IS +/-0.1 for u ** |
 |  |
| g-band: (gSM - gvst +0.45(g-r)SM+0.01) |
 |  |
| r-band: (rSM - rvst -0.1(g-r)SM+0.01) |
 |  |
| i-band: (iSM - ivst +0.125(r-i)SM-0.02) |
 |  |
| z-band: (zSM - zvst +0.12(i-z)SM-0.08) |
 |  |
Gaia - ATLAS Nightly (to Sept 2017); scale +/-0.05 except for u
Note that small offsets have been applied to g and r to ensure the mean offset is zero in the North (i and z were already zero)
| North | South |
|---|
| u-band: (Bpgaia - uvst + 1.2(Bp-Rp)gaia+0.6(Bp-Rp)2gaia-0.4) [only valid for 0.7 < (Bp-Rp) < 1.4] |
 |  |
| g-band: (Ggaia - gvst + 0.35(Bp-Rp)gaia+0.3(Bp-Rp)2gaia-0.0085*(Bp-Rp)5gaia-0.08) [only valid for 0.2 < (Bp-Rp) < 2.4] |
 |  |
| r-band: (Rpgaia - rvst + 0.30(Bp-Rp)gaia-0.08(Bp-Rp)2gaia+0.072*(Bp-Rp)3gaia+0.25) [only valid for 0.4 < (Bp-Rp) < 2.4] |
 |  |
| i-band: (Rpgaia - ivst - 0.03(Bp-Rp)gaia+0.03(Bp-Rp)2gaia+0.33) |
 |  |
| z-band: (Rpgaia - zvst - 0.01(Bp-Rp)gaia-0.14(Bp-Rp)2gaia_0.022(Bp-Rp)3+0.30) |
 |  |
For comparison, here are the GAIA -PS1 object by object comparisons:
See plot axes for colour equations. Range is 15<Rpgaia<17
| North | South |
|---|
| g-band: (Ggaia - gmeanpsfmagPS1) |
 |  |
| r-band: (Rpgaia - rmeanpsfmagPS1 |
 |  |
| r-band: (Ggaia - rmeanpsfmagPS1 |
 |  |
| i-band: (Rpgaia - imeanpsfmagPS1) |
 |  |
| i-band: (Ggaia - imeanpsfmagPS1) |
 |  |
| z-band: (Rpgaia - zmeanpsfmagPS1) |
 |  |
| z-band: (Ggaia - zmeanpsfmagPS1) |
 |  |
After calibration to extinction corrected GAIA, here are the residuals with extinction corrected PS1. Ideally these should not show any residual extinction pattern.
| EB-V: (this is the whole VST area - remember that the PS1 maps only cover a portion of each) |
 |  |
| g-band: (Bpgaia - gmeanpsfmagPS1, all extinction corrected) |
 |  |
| r-band: (Ggaia - rmeanpsfmagPS1, all extinction corrected) |
 |  |
| i-band: (Rpgaia - imeanpsfmagPS1, all extinction corrected) |
 |  |
| z-band: (Rpgaia - zmeanpsfmagPS1, all extinction corrected) |
 |  |
VST NGC median colour distributions - before and after NMs corrections
Sample: 15 < g_corrected < 18, classification_g==-1
| u-g (Nightly) | g-r (Nightly) | r-i (Nightly) | i-z (Nightly) |
|---|
 |  |  |  |
| u-g (Nightly+correction) | g-r (Nightly+correction) | r-i (Nightly+correction) | i-z (Nightly+correction) |
|---|
 |  |  |  |
| The plots below show the colour distributions after removing the expected extinction (based on the values for the VST filters that Joe Findlay produced) |
|---|
| u-g (Nightly+correction-0.915*EBV) | g-r (Nightly+correction-1.017*EBV) | r-i (Nightly+correction-0.532*EBV) | i-z (Nightly+correction-0.42*EBV) |
|---|
 |  |  |  |
VST SGC median colour distributions - before and after NMs corrections
| u-g (Nightly) | g-r (Nightly) | r-i (Nightly) | i-z (Nightly) |
|---|
 |  |  |  |
| u-g (Nightly+correction) | g-r (Nightly+correction) | r-i (Nightly+correction) | i-z (Nightly+correction) |
|---|
 |  |  |  |
| The plots below show the colour distributions after removing the expected extinction (based on the values for the VST filters that Joe Findlay produced) |
|---|
| u-g (Nightly+correction-0.915*EBV) | g-r (Nightly+correction-1.017*EBV) | r-i (Nightly+correction-0.532*EBV) | i-z (Nightly+correction-0.42*EBV) |
|---|
 |  |  |  |
THE VST ATLAS SURVEY
