astro::misc(3)

NAME

Astro::Misc - Miscellaneous astronomical routines

SYNOPSIS

use Astro::Misc;
$U = calc_U($flux, $dist, $freq);
($dist1, $dist2)=  kindist($ra,  $dec,  $vel,  $epoch,
$model);

DESCRIPTION

Astro::Misc contains an assorted set Perl routines for
doing various astronomical calculations.

AUTHOR

Chris Phillips phillips@jive.nl

FUNCTIONS read_possm

Read_possm interprets the output file from the AIPS POSSM task.
the task may be called repeatably if there is more than one

POSSM
output in the file. The file must be open before calling
read_possm, using the FileHandle module. The data from the possm
plot is returned in a hash. Some of the header values are re

turned
as scalar values while the actual plot values are returned as
references to arrays. The scalar values returned are:

SOURCE, DATE, TIME, BANDWIDTH, TYPE (='A&P'||'R&I')

The array references are: CHANNEL,

VELOCITY, FREQUENCY, AMPLITUDE, PHASE, ANTENNA

The global variable $Astro::Misc:oldpossm (default=0) controls

whether
old or new style possm plots are read. For oldpossm=1, one of
VELOCITY or FREQUENCY will be a reference to an empty list (but

the
hash value IS defined).

Usage: use FileHandle

my $fh = FileHandle->new();
my %ahash = ();
open($fh, 'possmfile');
read_possm($fh, %ahash);

Returns: 0 on success (but not hit eof)

1 on success (and hit eof)
2 on premature eof

Examples of hash usage:

$hash{SOURCE} # Source name
@{$hash{VELOCITY}} # Array of velocity values
${$hash{PHASE}}[4] # The fifth phase value

read_lovas

Read_lovas read the Lovas "Recommended Rest Frequencies for Ob

served
Interstellar Molecular Microwave Transitions - 1991 Revision"
(J. Phys. Chem. Ref. Data, 21, 181-272, 1992). Alpha quality!!

my @lovas = read_lovas($fname);
my @lovas = read_lovas($fname, $minfreq, $maxfreq);

calc_U

$U = calc_U($flux, $dist, $freq);

Calculate U (Excitation Parameter) for an UCHII region
Based on Eqn 8 in Schraml and Mezger, 1969

$flux Integrated Source Flux Density (Jy)
$dist Distance to source (kpc)
$freq Frequency of observation (GHz)

Note:

Uses the global variable $Astro::Misc::Temp for electron tem

perature
Default is 10000K

calc_Nl
$Nl = calc_Nl($U);

Calculate the Lyman continuum photon flux given U, the Excita

tion
Parameter for an UCHII region

$U is the Excitation Parameter (from calc_U)

Ref: Kurtz 1994 ApJS 91 p659 Eq (1) (Original Origin unknown)

lum2spectral
$spectral_type = lum2spectral($luminosity);

Calculate the spectral type of a ZAMS star from its luminosity
Based on Thompson 1984 ApJ 283 165 Table 1

$luminosity Star luminosity (normalised to Lsun)

Nl2spectral

$spectral = Nl2spectral($Nl);

Calculate the spectral type of a ZAMS star from its flux of
Lyman Continuum Photons (Nl)
Based on Panagia, 1973, ApJ, 78, 929

$Nl Flux of Lyman Continuum Photons

kindist

($dist1, $dist2)= kindist($ra, $dec, $vel, $epoch, $model);

Calculate the kinematic distance to an object

$dist1, $dist2 Near/Far distance (kpc)
$ra RA of object (turns)
$dec Dec of object (turns)
$vel LSR Velocity (km/s)
$epoch Epoch of coords (J2000/J/B1950/B)
$model Model to use (1 or 2)

Note:

Model 1 is based on Brand and Blitz, 1993, A&A, 275, 67-90.
Model 2 has unknown origin.

perl v5.8.0 2001-06-21 Astro::Misc(3)