building the hermes input catalog · hermes, 2013/06/05 selection of the reference band

Hermes, 2013/06/05 ftp://193.2.67.139/PSC_asc.tar.gz

Building the Hermes input catalog

1. Spectra of 1M stars are to be obtained in the four Hermes spectral bands;

2. resolving power of the spectra should be either 28,000 or 45,000;

3. S/N per resolution element in each spectral band should be at least 100;

4. the input catalogue should be drawn from a random magnitude-limited sample;

5. no color cuts shall be used;

6. the sample will be limited by celestial coordinates in the form of galactic longitude vs. lattitude lines: the adopted limiting lines shall delineate regions with

(i) high-enough altitude at culmination,(ii) high-enough stellar density for efficient observing, and(iii) low-enough average interstellar reddening for distant field stars.

1. Spectra of 1M stars are to be obtained in the four Hermes spectral bands;

2. resolving power of the spectra should be either 28,000 or 45,000;

3. S/N per resolution element in each spectral band should be at least 100;

4. the input catalogue should be drawn from a random magnitude-limited sample;

5. no color cuts shall be used;

6. the sample will be limited by celestial coordinates in the form of galactic longitude vs. lattitude lines: the adopted limiting lines shall delineate regions with

(i) high-enough altitude at culmination,(ii) high-enough stellar density for efficient observing, and(iii) low-enough average interstellar reddening for distant field stars.

TZ & the WG6 team


Selection of the reference band


Selection of the reference band

Blue band of Hermes falls between the Landoldt B and V bands.

prepared by U. Munari


Reddening vector & the stellar sequence


RA

VE

data

/2M

AS

S/r

edde

ning

/ebc

_gal

acti

c

Extinction estimate Schlegel et al. (1998) paper taken as a useful upper limit

E(B-V) = [0 ██ 0.025 █ 0.1 █ 0.4 █ 1.6 █ ∞]


RA

VE

data

/2M

AS

S/r

edde

ning

/ebc

_gal

acti

c_zo

om

Extinction estimate Schlegel et al. (1998) paper taken as a useful upper limit

E(B-V) = [0 ██ 0.05 █ 0.2 █ 0.8 █ 3.2 █ ∞]


B and V magnitudes: 2MASS vs. APASS


Comparison to spectroscopic temperatures


Photometric magnitude completeness


RA

VE

data

/2M

AS

S/r

edde

ning

/cou

ntpl

ot

2MASS: stellar density vs. Galactic latitude


Augmented 2MASS point source catalog: file structure

0.728276 -16.916227 00025478-1654584 15.359 14.627 14.531 AAA 222 0.728500 -16.905603 00025484-1654201 13.311 12.722 12.603 AAA 222 0.745089 -16.924509 00025882-1655282 12.978 12.660 12.616 AAA 222 0.746037 -16.903934 00025904-1654141 16.484 15.789 15.671 BBD 222 0.749757 -16.924177 00025994-1655270 16.670 16.600 15.128 BDU 220

75.168503 -75.058647 4174 17.802 19.073 4216 17.897 19.198 0.031 3 75.197432 -75.051080 4519 15.358 16.443 4567 15.453 16.569 0.031 0 75.191720 -75.075721 5832 14.141 14.726 5905 14.236 14.852 0.031 0 75.249153 -75.061398 -999 -999.000 -999.000 -999 -999.000 -999.000 0.031 3 75.205200 -75.078550 -999 -999.000 -999.000 -999 -999.000 -999.000 0.031 3

2MASS point source catalogue (files t*.cat)

R.A. Dec. Name J H K flag1 flag2

Photometry & effective temperature supplement (files r*.cat) | no reddening | maximum reddening |

Glon Glat Teff V B Teff V B E(B-V) flag

(uncompressed size: 67 Gbytes )


Temperatures from 2MASS

stars with |b| > 5o and V < 14


Astrometric match of 2MASS & APASS


Reddening does not jeopardize a good Vmag estimation for |b| > 5o.

Reddened stars are obviously dimmer, AK = 0.11 ↔ A

J = 0.17 ↔ A

V = 0.60 ↔ A

B = 0.79.

So, if selection is done on Vmag, we cover smaller distances (dreddened

/dunreddened

= 0.76 for A

V = 0.60 and d

reddened/d

unreddened = 0.57 for A

V = 1.20) and so a smaller volume.

Reddening and distances


CrowdingThe highest densities for at |b| > 5o are:

600 stars per degree2 for V < 12.5, 900 stars per degree2 for V < 13.0,1400 stars per degree2 for V < 13.5,2200 stars per degree2 for V < 14.0,

so we have < 13500 stars per degree2 for V < 16.0.

This highest density means that V < 16.0 stars are at an average distance of 31 arcsec.

So there is a (2/31)2 = 1/240 chance to have a superposition of our target with a V ~ 16 star (at a distance of ≤ 2 arcsec).

So we can expect that at this highest density typically one star per field suffers from < 10% flux contamination from a faint companion.

This is lower than a rate of (undetected) double-lined spectroscopic binaries. So crowdingdoes not seem to be a major problem at |b| > 5o.

building the hermes input catalog · hermes, 2013/06/05 selection of the reference band

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