[gnuastro-commits] master b3c8f20: Annum as unit of year in abbreviated CosmicCalculator units

[Mohammad Akhlaghi]

branch: master
commit b3c8f20525edc23c68c14dedc4ff4839831863f8
Author: Mohammad Akhlaghi <address@hidden>
Commit: Mohammad Akhlaghi <address@hidden>

    Annum as unit of year in abbreviated CosmicCalculator units
    
    Until now, we were simply using the non-standard "Gyr" for representing
    billion years. However, the official IAU-recognized abbreviation for year
    is "a" (for annum), and it is widely used in other scientific branches like
    geology, palaeontology, etc. The IAU published units are available here:
    https://www.iau.org/publications/proceedings_rules/units/
    
    Therefore with this commit, all mentions of "Gyr" in CosmicCalculator were
    corrected to "Ga". A short explanation is also added for those that may not
    be familiar with this standard: In the output of `--help', it is written as
    "Ga: Giga Annum". In the output with all measurements it is written as
    (Ga*), with the star pointing to a footnote in the end. And finally, in the
    book its written as "Ga (Giga annum, or billion years)".
    
    This issue was raised up by David Valls-Gabaud.
---
 bin/cosmiccal/args.h         |  6 +++---
 bin/cosmiccal/cosmiccal.c    |  9 ++++++---
 doc/announce-acknowledge.txt |  1 +
 doc/gnuastro.texi            | 14 +++++++-------
 4 files changed, 17 insertions(+), 13 deletions(-)

diff --git a/bin/cosmiccal/args.h b/bin/cosmiccal/args.h
index 6c7d5cd..12d7c57 100644
--- a/bin/cosmiccal/args.h
+++ b/bin/cosmiccal/args.h
@@ -110,7 +110,7 @@ struct argp_option program_options[] =
       UI_KEY_AGENOW,
       0,
       0,
-      "Age of universe now (Gyr).",
+      "Age of universe now (Ga: Giga Annum).",
       UI_GROUP_SPECIFIC,
       &p->specific,
       GAL_OPTIONS_NO_ARG_TYPE,
@@ -222,7 +222,7 @@ struct argp_option program_options[] =
       UI_KEY_AGE,
       0,
       0,
-      "Age of universe at z (Gyr).",
+      "Age of universe at z (Ga: Giga Annum).",
       UI_GROUP_SPECIFIC,
       &p->specific,
       GAL_OPTIONS_NO_ARG_TYPE,
@@ -236,7 +236,7 @@ struct argp_option program_options[] =
       UI_KEY_LOOKBACKTIME,
       0,
       0,
-      "Look back time to z (Gyr).",
+      "Look back time to z (Ga: Giga Annum).",
       UI_GROUP_SPECIFIC,
       &p->specific,
       GAL_OPTIONS_NO_ARG_TYPE,
diff --git a/bin/cosmiccal/cosmiccal.c b/bin/cosmiccal/cosmiccal.c
index 1ce4ad2..49a4929 100644
--- a/bin/cosmiccal/cosmiccal.c
+++ b/bin/cosmiccal/cosmiccal.c
@@ -113,7 +113,7 @@ cosmiccal_printall(struct cosmiccalparams *p)
 
   printf("\n\n Universe now\n");
   printf(    " ------------\n");
-  printf(FLTFORMAT, "Age of Universe now (Gyr):", curage);
+  printf(FLTFORMAT, "Age of Universe now (Ga*):", curage);
   printf(EXPFORMAT, "Critical density now (g/cm^3):",  ccritd);
   printf(FLTFORMAT, "Proper distance to z (Mpc):", pd);
   printf(FLTFORMAT, "Angular diameter distance to z (Mpc):", ad);
@@ -127,13 +127,16 @@ cosmiccal_printall(struct cosmiccalparams *p)
 
   printf("\n\n Universe at desired redshift z\n");
   printf(    " ------------------------------\n");
-  printf(FLTFORMAT, "Age of Universe at z (Gyr):", outage);
-  printf(FLTFORMAT, "Look-back time to z (Gyr):", curage-outage);
+  printf(FLTFORMAT, "Age of Universe at z (Ga*):", outage);
+  printf(FLTFORMAT, "Look-back time to z (Ga*):", curage-outage);
   printf(EXPFORMAT, "Critical density at z (g/cm^3):",  zcritd);
 
   printf("\n\n Comoving universe (time independent)\n");
   printf(    " ------------------------------------\n");
   printf(FLTFORMAT, "Comoving volume over 4pi stradian to z (Mpc^3):", vz);
+
+  printf("\n-------\n");
+  printf("*: Ga is short for Giga Annum, or billion years (IAU standard).\n");
 }
 
 
diff --git a/doc/announce-acknowledge.txt b/doc/announce-acknowledge.txt
index 0b5a011..2a42585 100644
--- a/doc/announce-acknowledge.txt
+++ b/doc/announce-acknowledge.txt
@@ -8,3 +8,4 @@ Johan Knapen
 Mamta Pommier
 Michael Stein
 Ignacio Trujillo
+David Valls-Gabaud
diff --git a/doc/gnuastro.texi b/doc/gnuastro.texi
index a4d4e01..b6257cf 100644
--- a/doc/gnuastro.texi
+++ b/doc/gnuastro.texi
@@ -21629,8 +21629,8 @@ option which has the units along with a short 
description.
 
 @item -G
 @itemx --agenow
-The current age of the universe (given the input parameters) in Giga-years
-(Gyr).
+The current age of the universe (given the input parameters) in Ga (Giga
+annum, or billion years).
 
 @item -C
 @itemx --criticaldensitynow
@@ -21673,14 +21673,14 @@ the apparent magnitude to give the object's absolute 
magnitude.
 
 @item -g
 @itemx --age
-Age of the universe at given redshift in Giga-years (Gyr).
+Age of the universe at given redshift in Ga (Giga annum, or billion years).
 
 @item -b
 @itemx --lookbacktime
-The look-back time to given redshift in Giga-years (Gyr). The look-back
-time at a given redshift is defined as the current age of the universe
-(@option{--agenow}) subtracted by the age of the universe at the given
-redshift.
+The look-back time to given redshift in Ga (Giga annum, or billion
+years). The look-back time at a given redshift is defined as the current
+age of the universe (@option{--agenow}) subtracted by the age of the
+universe at the given redshift.
 
 @item -c
 @itemx --criticaldensity