From X-ray to Infrared

Today, from the CANDELS blog, I get this amazing animation, which include the images from X-ray to infrared bands. It is obvious that the HST optical image has the highest quality. What's more, you can see that different emissions come from different part of the galaxies due to their different origins. It is quite interesting that the Herschel has a high detection threshold but low resolution, so the objects are blended with each other.This is the reason why Herschel cannot do deep field observations.

This animation starts with an X-ray image from the Chandra telescope,
showing two sources which probably harbor central black holes. It then
transitions to the Hubble images, where you can see that some of the
galaxies have spiral features and others don't. It then transitions to the
infrared images from the Spitzer, and finally the Herschel observatory.
You can see that the resolution of the infrared images is much poorer
than the Hubble images -- the galaxies are all blended together.
Nevertheless, you can make out that some galaxies are "bluer" than
others at infrared wavelengths. Looking at the last image, you can convince
yourself that the brightest source of far-infrared radiation in this image
(which comes primarily from heated dust) is probably the galaxy just
below the center, which is also an X-ray sources.

From http://candels-collaboration.blogspot.com/2013/07/the-end-is-just-beginning.html

How to get the luminosity function from a lensed field

I just want to try to recall the discussion in last week. However, there are still things I have lost.

There could be two methods to complete this job in my knowledge.

(1)  The luminosity function can be described as a formula with several parameters, so you just need to estimate the values to solve the problem. By comparing the lensed luminosity function based on the lensing map and  the observed number density of galaxies, you can get the best fit parameters.

(2)  for each point in the lensed field, you have already known the magnification and you can obtain the volume and the magnitude limit. So you can repeat this process for the whole field to get the real volume for a particular magnitude range. You may know what to do next. Just use the simple equation desity = N/V.

 

A good example of HOW is Neutral Hydrogen in the Universe

Today the website of astrobites introduces the work of Harvard graduate student Yuan-Sen Ting.
I do not want to say too much about the Neutral Hydrogen, but I 'd like to mention the website created by the author ( https://www.cfa.harvard.edu/~yuan-sen.ting/lyman_alpha.html).

Every day, we should face several bytes of data. Many of them are just numbers, so is there any way to make it better? This author give us a good example to show the results. In fact the website is just one part of the Harvard course. But if we also plot such beautiful plots in our work our just display  our work in such a hommized way. Won't it be fun?

http://astrobites.org/2013/07/14/astrophysical-classics-neutral-hydrogen-in-the-universe-part-1/