J/MNRAS/326/1161 ROSAT medium-sensitivity Galactic plane survey (Morley+, 2001)
A ROSAT medium-sensitivity Galactic plane survey at 180°<l<280°.
Morley J.E., Briggs K.R., Pye J.P., Favata F., Micela G., Sciortino S.
<Mon. Not. R. Astron. Soc. 326, 1161 (2001)>
=2001MNRAS.326.1161M 2001MNRAS.326.1161M
ADC_Keywords: Surveys ; Stars, late-type ; X-ray sources ; Photometry
Keywords: catalogues - surveys - stars: late-type - Galaxy: stellar content -
X-rays: general
Abstract:
We have performed a moderately deep soft X-ray (0.1-2keV) survey of
the Galactic plane using pointed observations with the ROSAT Position
Sensitive Proportional Counter (PSPC). The survey is more than an
order of magnitude more sensitive than previous X-ray surveys near the
Galactic plane. The data consist of nine fields each of ∼10ks
exposure, pointed at positions on or very close to the Galactic plane
(|b|<0.3°) in the longitude range 180°≲l≲280°. This
region has relatively low X-ray absorbing material out to distances of
several hundred pc and presents fewer source-confusion problems than
at other longitudes. The total sky area surveyed was 2.5deg2 this
yielded 93 sources, 89 of which were detected in the hard (0.4-2.0keV)
band. Nine sources were detected in both soft (0.1-0.4keV) and hard
bands. In the hard band, the survey coverage is 90 per cent for
sources brighter than 0.002count/s (∼2x10-14erg/cm2/s), but falls
steeply below this value, with the weakest sources being
∼0.001count/s. The median limiting flux is ≲0.0013count/s
(∼1.3x1014erg/cm2/s). There are 64 sources with hard-band count
rates >0.002count/s. We present the catalogue of X-ray sources and the
number-flux relations (logN-logS). Eighteen sources have possible
identifications from the SIMBAD data base. We have searched the
Tycho-2 (Cat. I/259) and USNO-A2.0 (Cat. I/252) catalogues to find
all possible optical counterparts brighter than 19th magnitude, and
attempt to classify these on the basis of log(FX/Fopt) versus optical
colour diagrams and near-infrared photometry from the 2MASS Second
Incremental Data Release (Cat. <B/2mass>). Hence, we have found the
majority of these sources to be consistent with being late-type
main-sequence stars, as previous studies have proposed from
incompletely identified surveys. Comparison of the measured
number-flux relations with predictions of Galactic (stellar) and
extragalactic populations supports the view that the population of
young stars in the plane is denser than previously thought.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table23.dat 89 93 Sources detected in the hard band (0.4-2keV)
table4.dat 172 317 Possible optical and near-infrared counterparts
to X-ray sources detected in this survey
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See also:
IX/30 : Second ROSAT PSPC Catalog (ROSAT, 2000)
Byte-by-byte Description of file: table23.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- [MBP2001] Source number
4 I1 --- Field Field number
6- 7 I2 h RAh Right ascension (J2000)
9- 10 I2 min RAm Right ascension (J2000)
12- 16 F5.2 s RAs Right ascension (J2000)
18 A1 --- DE- Declination sign (J2000)
19- 20 I2 deg DEd Declination (J2000)
22- 23 I2 arcmin DEm Declination (J2000)
25- 28 F4.1 arcsec DEs Declination (J2000)
30- 36 F7.3 deg GLON Galactic longitude
38- 43 F6.3 deg GLAT Galactic latitude
45- 49 F5.2 --- SigH ? Significance of detection in Hard band
in equivalent Gaussian σ
50 A1 --- n_SigH [*] *=99% significance of detection in H band
52 A1 --- l_CRH Limit flag on CR
53- 56 F4.1 ct/ks CRH Count Rate in Hard (0.4-2keV) band
58- 61 F4.1 ct/ks e_CRH ? rms uncertainty on CRH
63 A1 --- Note [ST] Notes (1)
65- 69 F5.2 --- SigS ? Significance of detection in Soft band
in equivalent Gaussian σ
71- 73 F3.1 ct/ks CRS ? Count Rate in Soft (0.1-0.4keV) band
75- 77 F3.1 ct/ks e_CRS ? rms uncertainty on CRS
79 A1 --- l_HR Limit flag on HR
80- 84 F5.2 --- HR ? Hardness ratio, HR=(H-S)/(H+S)
86- 89 F4.2 --- e_HR ? rms uncertainty on HR
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Note (1): Band of detection as follows:
S = source was detected in the soft band (0.1-0.4keV)
T = source was detected in the total band (0.1-2keV)
else hard band (0.4-2keV) (H)
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- [MBP2001] Number
4 A1 --- m_[MBP2001] Letter running in alphabetical order with
separation from X-ray source position
6- 7 I2 h RAh ? Optical right ascension (J2000.0)
9- 10 I2 min RAm ? Optical right ascension (J2000.0)
12- 16 F5.2 s RAs ? Optical right ascension (J2000.0)
18 A1 --- DE- Optical declination sign (J2000.0)
19- 20 I2 deg DEd ? Optical declination (J2000.0)
22- 23 I2 arcmin DEm ? Optical declination (J2000.0)
25- 28 F4.1 arcsec DEs ? Optical declination (J2000.0)
30- 33 F4.1 arcsec Sep ? Separation from X-ray source position
35 A1 --- r_RAh [UTS2] Source of position and optical
photometry (1)
37- 40 F4.1 mag VRmag ? Optical magnitude
(V from Tycho2 or R from USNO-A2.0)
42- 45 F4.1 mag B-VR ? Optical colour
(B-V from Tycho2 or B-R from USNO-A2.0)
47 A1 --- l_FX/Fopt Limit flag on logFX/Fopt
48- 52 F5.2 [-] FX/Fopt ? X-ray to optical flux ratio
(logFX/FV from Tycho2 or
logFX/FR from USNO-A2.0)
54 A1 --- CL [CENU] Classification from logFX/Fopt versus
colour diagram (2)
55 A1 --- l_Jmag Limit flag on Jmag
56- 60 F5.2 mag Jmag ? J magnitude
62 A1 --- l_J-H Limit flag on J-H
63- 67 F5.2 mag J-H ? J-H colour index
69- 72 F4.2 mag e_J-H ? rms uncertainty on J-H
74 A1 --- l_H-Ks Limit flag on H-Ks
75- 79 F5.2 mag H-Ks ? H-Ks colour index
81- 84 F4.2 mag e_H-Ks ? rms uncertainty on H-Ks
86 A1 --- MS [YN?] Position on a near-IR two-colour
diagram is consistent with an MS star flag
88- 93 A6 --- SpType Spectral type (3)
95-174 A80 --- Notes Notes (luminosity units are erg/s=10-7W)
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Note (1): Source of position and optical photometry as follows:
U = USNO-A2.0, Cat. I/252
T = Tycho-2, Cat. I/259
S = SIMBAD
2 = 2MASS, Cat. <B/2mass>
Note (2): Classification as follows:
C = Coronal. A candidate is classed coronal if:
(a) it falls in the coronal zone of the Tycho-2 log(FX/Fopt)
versus B-V or USNO-A2.0 log(FX/FR) versus B-R diagram and any
available 2MASS photometry does not rule out an MS star; or
(b) it falls in the no mans land region of the log(FX/FR) versus
B-R and 2MASS photometry is consistent with that of an MS
star. Where there is no coronal candidate, we have taken the
classification of the brightest candidate in the error circle.
E = Extragalactic. A candidate is classed extragalactic if:
it falls in the extragalactic zone of the log(FX/FR) versus B-R
diagram or appears in 2MASS only. Note that the most active
late-type stars may be counted as extragalactic if their USNO
colours are erroneously blue, but the 2MASS colours should
discriminate between the galaxies and the latest-type stars, and
any candidates we misclassify in this way must be emitting above
their nominal saturation threshold. It is possible that embedded
objects, such as protostars, may also be erroneously included in
this class. There are several objects around the H II region
associated with source 11 that are seen only in 2MASS with very
red colours; these are possibly embedded objects, but unlikely to
contribute to the X-ray flux of source 11, as the H II region is
too distant.
N = No mans land candidates are those that fall into that region of
the log(FX/FR) versus B-R diagram and have either no or non-MS
2MASS photometry.
U = Other classifications (e.g. early-type stars, and H II regions)
come from SIMBAD, while Unidentified sources are those for which
we could find no potential counterpart.
Note (3): Spectral type estimated from near-IR photometry using the MS colours
table of Bessell & Brett (1988PASP..100.1134B 1988PASP..100.1134B), unless the luminosity
class is given, whereby the spectral type is taken from SIMBAD.
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History:
* 30-Jan-2002: From electronic version of the journal
* 10-Mar-2006: In table4, for object 11A, H-Ks=2.13±>-0.26
modified in H-Ks=2.13±0.26
(End) James Marcout, Patricia Bauer [CDS] 30-Jan-2002