The Tadpole Galaxy

The tadpole galaxy: HST data processed with

PixInsight

Mehdi Bozzo-Rey, [email protected]

About the tadpole galaxy● Other “names” :

○ UGC 10214- Uppsala General Catalog of Galaxies (12921 galaxies - northern hemisphere)○ Arp 188 - Atlas of Peculiar Galaxies, produced by Alton Arp (338 galaxies)○ PGC 57129 - Catalog of principal galaxies (73 197 galaxies)

● Distance: 420 million light years● redshift: z=0.031358

Mehdi Bozzo-Rey: [email protected]

about the tadpole galaxy - spitzer (Infrared)


Redshift and the police car● Doppler effect:

○ when the police car comes towards you at high speed : increased pitch (high frequency, which means shorter wavelength)

○ after the police car passes by : decrease in pitch (lower frequency, which means higher values for the wavelength)

● Sound and light : both waves, the same process applies● for the light: shorter wavelength = blue shift, if the wavelength has higher

values = red shift● If an object goes away from you: redshift. If it is going towards you: blueshift


http://www.space.com/25732-redshift-blueshift.html

http://www.space.com/25732-redshift-blueshift.html

What can you do when you know the redshift ?● You can calculate how fast a galaxy is moving away from you !● When z is small compared to 1 (which is our case) the velocity of the galaxy is

given by : v=c z, where c is the speed of light● v = 300 000 * 0.031358 = 9407 km/s !


How old is that picture, anyway ?● Distances in astronomy always relate to time as light travels at a finite speed

(300 000 km/s)● 425 Mly means … the light the HST caught left the galaxy before … we even

had dinosaurs on earth !


425 Mly … Silurian


425 Mly … arthropods


tadpole galaxy: how to get the data (1)


tadpole galaxy: how to get the data (2)


One last word about PixInsight and image processing From the PixInsight forum:


PixInsight : loading the data


STF - Autostretch


dynamic crop


STF - autostretch again


DBE - sample generation


DBE : tolerance


DBE: sample weight


DBE: not in background


DBE: image correction


DBE: extracted background


DBE: before / after


background neutralization: preview


background neutralization: using the preview as ROI


color calibration


autostretch again (unlink channels)


sampleformat conversion: convert to 64bit image


save STF process


rename STF icon


reinject STF process in histogram transformation (1)


reinject STF process in histogram transformation (2)


apply histogram transformation and disable stf (F12)


masks: luminance or lightness ? (1)Extracting lightness


masks: luminance or lightness ? (2)extracting luminance


masks: luminance or lightness ? (3)luminance vs lightness


Things to remember when creating masks● We need at least 2 masks: one for the structure, one for the background● What is black will stop the process from being executed in this area● What is white acts as an open window in front of the picture: the

process/transformation will be executed in this area● There are multiple ways of building masks, channel extraction for luminance /

lightness with histogram transformations is the easiest way● You may need more than 2 masks in order to achieve the best results !


clone luminance, invert and rename


histogram transformation - luminance mask


histogram transformation - inverted luminance mask


HDR multiscale transform - luminance mask


HDR multiscale transform - final


what happened ??? - tip of the day● if you apply a mask and then duplicate a preview, the mask is lost ! It is

equivalent to applying your process on the preview, using a white mask (i.e. no mask) the size of the preview

● the right way to test is to apply the transformation on the preview and then reset the preview (you can duplicate the transformed preview in order to “save” it)

● conclusion: we need a new mask :-)● The idea is that the original mask is “not white enough” for the core of the

galaxy


luminance “core” mask


HDR using our new “core” mask


you can play with the masks ...


curves transformation - inverted lum mask - readout


curves transformation - background final


curves transformation - core


Noise reduction:ACDNR - background - previews (1)


Noise reduction:ACDNR - background - previews (2)


ACDNR - background - full image


ACDNR - core- luminance mask (not lum_core)


color saturation - luminance mask


Histogram transformation - luminance mask


curves transformation - luminance mask - blue boost


the tadpole galaxy published by NASA


Our tadpole galaxy


details - NASA


Our tadpole core


saving the final image


The Tadpole Galaxy

Documents

Transcript of The Tadpole Galaxy