<p>Say, if I downloaded the CMB frame redshifts of some galaxies from <a href="https://ned.ipac.caltech.edu/" rel="nofollow noreferrer">NED</a> database, then what is the procedure to correct it for coherent flows?</p>
<p>I'm using the <a href="https://csp.obs.carnegiescience.edu/data/snpy" rel="nofollow noreferrer">SNooPy</a>(snpy) Python package to analyze some Type Ia supernova data collected from <a href="https://csp.obs.carnegiescience.edu/data/CSP_Photometry_DR3.tgz/view" rel="nofollow noreferrer">CSP</a> archive. snpy provides a method called <a href="https://users.obs.carnegiescience.edu/cburns/SNooPyDocs/html/snpy.html?highlight=get_zcmb#snpy.sn.sn.get_zcmb" rel="nofollow noreferrer">sn.get_zcmb()</a> to collect the redshift of the SNe Ia host galaxy corrected to CMB frame from NED calculator. Now, for cosmological studies mere z_cmb isn't enough, we need to correct it for bulk coherent flow as per literature. But the procedure to correct for it isn't known to me.</p>

CC BY-SA 4.0
2022-04-19T12:36:07.363Z
Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking.
Community
CC BY-SA 4.0
2022-04-23T08:56:31.050Z
CMB frame redshifts are already corrected for large-scale flows; that’s why they have that name.
Peter Erwin
<cosmology><redshift><velocity><cosmic-microwave-background>
How are CMB frame redshifts of galaxies corrected for coherent flows?
gautam bhuyan
# How are CMB frame redshifts of galaxies corrected for coherent flows?

(Asked by: username_0 on 2022-04-19)

Say, if I downloaded the CMB frame redshifts of some galaxies from [NED](https://ned.ipac.caltech.edu/) database, then what is the procedure to correct it for coherent flows?

I'm using the [SNooPy](https://csp.obs.carnegiescience.edu/data/snpy)(snpy) Python package to analyze some Type Ia supernova data collected from [CSP](https://csp.obs.carnegiescience.edu/data/CSP_Photometry_DR3.tgz/view) archive. snpy provides a method called [sn.get\_zcmb()](https://users.obs.carnegiescience.edu/cburns/SNooPyDocs/html/snpy.html?highlight=get_zcmb#snpy.sn.sn.get_zcmb) to collect the redshift of the SNe Ia host galaxy corrected to CMB frame from NED calculator. Now, for cosmological studies mere z\_cmb isn't enough, we need to correct it for bulk coherent flow as per literature. But the procedure to correct for it isn't known to me.

**Tags:** cosmology, redshift, velocity, cosmic-microwave-background

> **Comments:**
> **username_1**: Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking.  
> **username_2**: CMB frame redshifts are already corrected for large-scale flows; that’s why they have that name.  

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## 0 answers

