An X-ray spectral survey of the disc of M31 with XMM-Newton
L. Shaw Greening, R. Barnard, U. Kolb, C. Tonkin, J.P. Osborne
aa r X i v : . [ a s t r o - ph ] A ug Astronomy&Astrophysicsmanuscript no. m31˙13Aug˙astroph c (cid:13)
ESO 2018June 7, 2018
An X-ray spectral survey of the disc of M31 with XMM-Newton
L. Shaw Greening , R. Barnard , U. Kolb , C. Tonkin , and J.P. Osborne The Department of Physics and Astronomy, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK The Department of Physics and Astronomy, The University of Leicester, Leicester, LE1 7RH, UKReceived date / Accepted date
ABSTRACT
Aims.
We present the results of a complete spectral survey of the X-ray point sources detected in five XMM-Newton observationsalong the major axis of M31 but avoiding the central bulge, aimed at establishing the population characteristics of X-ray sources inthis galaxy.
Methods.
We obtained background subtracted spectra and lightcurves for each of the 335 X-ray point sources detected across thefive observations from 2002. We also correlate our source list with those of earlier X-ray surveys and radio, optical and infra-redcatalogues. Sources with more than 50 source counts are individually spectrally fit in order to create the most accurate luminosityfunctions of M31 to date.
Results.
Based on the spectral fitting of these sources with a power law model, we observe a broad range of best fit photon index.From this distribution of best fit index, we identify 16 strong high mass X-ray binary system candidates in M31. We show the firstcumulative luminosity functions created using the best fit spectral model to each source with more than 50 source counts in the disc ofM31. The cumulative luminosity functions show a distinct flattening in the X-ray luminosity L X interval 37 . . log L X erg s − . . X ∼ . × erg s − the observed population isstatistically dominated by the point source population of M31. Key words.
Galaxies: individual: M31 - X-rays: general - X-rays: binaries
1. Introduction
The Andromeda Galaxy (M31) is the nearest spiral galaxy toour own, lying at a distance of 760 kpc (van den Bergh 2000).The sources in M31 are observed at a nearly uniform distanceand through an absorption column significantly lower than forsources in the Galactic plane. Thus M31 is an ideal target forstudying the emission from the X-ray point sources in a galaxysimilar to the Milky Way.M31 has been observed with many X-ray observatoriessince
Einstein , when van Speybroeck et al. (1979) observed69 point sources above 5 × erg s − . Two ROSAT sur-veys (Supper et al. 1997, 2001) covered most of the M31 discand found 560 sources above 5 × erg s − . There havealso been many Chandra (e.g. Williams et al. 2004; Kong et al.2002, 2003) and XMM-Newton (e.g. Trudolyubov et al. 2006;Pietsch et al. 2005; Osborne et al. 2001; Shirey et al. 2001) sur-veys of both the disc and central region of M31.The X-ray emission from M31 is dominated by pointsources mostly consisting of X-ray binary systems (XBs).Trudolyubov et al. (2006) surveyed 123 sources in the central re-gion of M31 and reported that the majority have X-ray propertiesreminiscent of Galactic low mass XBs (LMXBs), and labelled44 sources as XB candidates based on their spectral propertiesand variability.Six neighbouring, slightly overlapping XMM-Newton obser-vations along the major axis of M31 were made in January andJune 2002. These observations, along with others taken between2000 and 2007, form part of a survey of the whole optical D ellipse of M31. Since the central region of M31 is well studiedand the wider survey has not been completed at the time of this work, we have investigated the five remaining major axis obser-vations that exclude the core region. Henceforth we refer to thesefields as the M31 disc fields. These observations were long anduninterrupted; together with the unprecedented e ff ective area ofXMM-Newton, they yielded up to 40 times the photon counts ofthe best previous observations. Previous work on these XMM-Newton fields (see e.g. Pietsch et al. 2005; Trudolyubov et al.2002) has derived only spectral properties for the brightest fewsources.In this paper we re-analyse the five M31 disc fields. Forthe first time we extend the spectral analysis to sources downto L X & erg s − . We create a new source list, derive thespectral parameters of each source and create spatially resolvedcumulative X-ray luminosity functions (CLFs). In Sect. 2 wegive details of the observations and data reduction, Sect. 3 cov-ers the analysis and the results of cross correlations with thePietsch et al. (2005) catalogue and catalogues at other wave-lengths. In Sect. 4 we give details of the analysis of our spec-tral fitting including the creation of CLFs and comments on thecontamination of the CLF by background AGN. Finally, Sect. 5summarises our findings.
2. Observations and Data Reduction
One observation of each disc field of M31 was taken usingthe EPIC pn (Str¨uder et al. 2001) and MOS (Turner et al. 2001)cameras on XMM-Newton in January and June 2002; a jour-nal of the observations is presented in Table 1. From northto south, we refer to the fields as North 3, North 2, North1, South 1 and South 2. Data were processed using XMM-Newton SAS (version 6.5.0) tasks epproc and emproc with up
L. Shaw Greening et al.: An X-ray spectral survey of the disc of M31 with XMM-Newton to date calibration. There are also multiple observations of thecentral region taken between 2000 and 2005; these have beenanalysed by Trudolyubov et al. (2002), Pietsch et al. (2005) andTrudolyubov et al. (2006) and are not covered here.
For the purposes of source detection, the observations werescreened for periods of high background counts in each cam-era. Lightcurves including all counts above 10 keV were cre-ated for each camera, and intervals with levels above 1 counts − for the pn and 0.5 counts s − for each of the MOS cam-eras were excluded. Observations were then synchronised andsource detection carried out. For the source detection the datawere split into 5 energy bands: (0.2-0.5) keV, (0.5-2) keV, (2-4.5) keV, (4.5-7) keV and (7-12) keV. For the pn data we usedonly “single” events (PATTERN ==
0) in the first energy bandand for the other bands “singles and doubles” were selected(PATTERN < = >
12) for the pn were used and to avoid emission fromthe spatially inhomogeneous Copper fluorescent line, the energyrange (7.8-8.2) keV was omitted from band 5. For MOS data“singles” to “quadruples” (PATTERN < =
12) were selected. Foreach camera, source lists were constructed in each energy bandusing edetect chain with a minimum likelihood threshold of10. These lists were then combined to form a final source list.All source regions were then set to have a radius of 40 ′′ as thiscorresponds to ∼
88% encircled energy at 1.5 keV. Finally thesources in this list were visually inspected for overlapping sourceregions. When a 40 ′′ source extraction region contained morethan one source, the region was reduced to 20 ′′ . Any 20 ′′ extrac-tion region containing more than one source was deleted. Backgrounds were selected for each source based on the follow-ing criteria. Suitable backgrounds must be on the same CCD asthe source, have no sources within the background region, andmust have a lower count density (fewer counts per unit area) thanthe source region. The latter criterion ensures that there are nounresolved faint sources or areas of di ff use emission in the back-ground region that combine to an anomalously high count den-sity. For source regions on a chip gap or chip edge backgroundregions must be on the same chip edge or gap and have the samepercentage of o ff -chip area as the source region. Finally, back-ground regions have a radius between one and four times theradius of the source extraction region. Following Barnard et al. (2007b), synchronised source andbackground lightcurves with 2.6 s time resolution were extractedfrom each of the three detectors. These were summed to givea combined, background subtracted EPIC lightcurve for everysource.Energy spectra were extracted from the source and back-ground regions with 5 eV binning for the pn camera and with15 eV binning for the MOS cameras. A response matrix (RMF)and ancillary response file (ARF) were also generated for eachsource spectrum. For any source with spectra from both the MOScameras we added together the two spectra to form a combinedMOS spectrum, otherwise just the one MOS spectrum was used http: // xmm.vilspa.esa.es / sas / / doc / edetect chain / index.html in the following analysis. Counts outside the 0.3-10 keV rangewere rejected.
3. Analysis
There were 335 point source detections with a minimum like-lihood of 10 in the 5 disc fields of M31. These sources are or-dered by RA and we present their positions and X-ray propertiesin Table A.1. Of these 335 detections, 6 sources were detectedin two observations and so there are 329 distinct point sourcesacross the disc. Their count rates range from 3 . × − to 0.403counts per second. Lightcurves were binned to 100, 200 and 400 second bins andchecked for variability by examining how well they were fit by aline of constant intensity. Sources with a null hypothesis proba-bility of > ±
3% rms variability.
222 of the sources in the disc of M31 have spectra with su ffi cientphotons ( >
50 source counts in the pn or combined MOS) to al-low spectral fitting, the results of which are given in Table A.1.We binned the pn and MOS spectra depending on source in-tensity. Spectra exceeding 500 source counts over the observa-tion were grouped to a minimum of 50 counts per bin. Spectracontaining between 200 and 499 source counts were grouped toa minimum of 20 counts per bin. Spectra with between 50 and199 source counts and with more than 50% of the total countsfrom the source were grouped to a minimum of 10 counts perbin, while those with between 50 and 199 source counts butwith less than 50% of the total counts from the source were alsogrouped to a minimum of 20 counts per bin. Each grouped en-ergy spectrum was freely fit by three spectral models: blackbody,bremsstrahlung and power law emission models, using xspec11.3.1 . Sources which have very few or no counts above 2 keVwere also fit with a neutron star atmosphere (nsa) model whichresembles the emission from a super soft source. For all the mod-els the absorption was a free parameter but with a minimumof at least 0 . × cm − , the Galactic foreground absorption(Dickey & Lockman 1990). The source flux was calculated fromthe best fit model. The spectral parameters of each source givea greater insight into its properties than its X-ray hardness ratiosor variability alone. Sources with less than 50 source counts inboth cameras are dealt with on a field by field basis as describedbelow. For the 95 detections with too few photons to allow spectral fit-ting ( <
50 source counts in both cameras), the parameters of http: // heasarc.gsfc.nasa.gov / docs / xanadu / xspec / index.html. Shaw Greening et al.: An X-ray spectral survey of the disc of M31 with XMM-Newton 3 Table 1.
Journal of XMM-Newton Observations of M31. The field, observation number, date, pointing direction, filter used, totalexposure (Exp) and exposure of the good time interval (GTI) and the number of sources detected are given.
Field Observation Date Pointing direction Filter Exp GTI SourcesRA / dec (J2000) ks ksNorth 3 (n3) 0109270401 29 June 2002 0:46:38 + + + + + Table 2.
Best fit parameters for power law models applied to the summed spectra of the faint sources in each of the disc fields. Weshow the total number of faint sources in each field, the power law photon index, Γ , χ / dof and for which camera this fit was found.The absorption was fixed to 0 . × H atom cm − for each field. The bracketed numbers are the error in the last significantfigure. Where we quote two conversion factors, the first is for the pn camera and the second for the MOS. Errors are unavailable forthe best fit power law index to South 1 as the χ / dof is > Field Number of Γ χ / dof Camera(s) used Conversion Factorfaint sources erg s − / counts s − North 3 19 2.8(13) 161 /
122 pn / MOS 5 . × / . × North 2 32 1.5(4) 39 /
38 pn / MOS 3 . × / . × North 1 11 1.00(15) 24 /
16 MOS 5 . × South 1 16 1.3(-) 450 /
120 pn 4 . × South 2 17 1.3(4) 56 /
46 pn 4 . × the best fit absorbed power law for the field were used. First wegrouped the spectra according to field and camera (pn or MOS),creating 10 groups. The spectra of the faint sources in each groupwere then summed to give one spectrum for each camera’s ob-servation of every field. The absorption was fixed to 0.1 × H atoms cm − and the best fit photon index to the summed spec-trum was used to calculate a count rate to flux conversion for thatcamera’s observation of the field. For South 1 we do not quoteerrors on the photon index because the χ / dof is >
2. Althoughthis is not a good fit to the South 1 sources, it is the best fitpower law and so we have used it to maintain consistency acrossthe fields.Some sources are detected only on the pn or one of the MOScameras and not in all three. For some fields only one of the twosummed spectra (pn or MOS) could be well fit using a powerlaw model. Where a faint source is detected in one camera buta good fit to the summed faint source spectrum for that fieldis only available for the other camera we do not give a sourceluminosity.The parameters of the best fit power law to each field aregiven in Table 2. For the faint sources the quoted conversion fac-tor was applied to the exposure corrected count rate. There is anobvious change in the photon index in the northern disc: withincreasing distance from the centre of M31 the best fit powerlaw becomes softer. However we caution against drawing con-clusions from this as it is based on the summed spectrum of asmall number of faint sources and the photon indicies are con-sistent with each other within errors.We have calculated the 0.3-10 keV luminosity from either asource spectrum or from an average model for the relevant field,for 317 of the 329 sources, and these are given in Table A.1.
We searched for cross-correlations within a radius of3(( σ statistical ) + ( σ systematic ) ) / , where, for the uncorrectedXMM-Newton positions from this survey, σ statistical = ′′ and σ systematic = ′′ . The statistical error is taken from the 2XMMcatalogue . This error is strongly dependent on source counts,however for our range of source count rates we have assumed arepresentative value of 1 arcsecond for the statistical error. Thesystematic error is derived from the o ff set to each field. Themost accurate XMM-Newton positions have residual system-atic errors of around 0 . ′′ , and it can be seen from Pietsch et al.(2005) that the M31 disc fields each have an additional o ff setof 0 . − . ′′ . Thus we have used a conservative systematic er-ror of 3 ′′ . This gives a search radius of 10 ′′ . For 295 out of our329 sources we found a source within the search radius in thePietsch et al. (2005) catalogue, and a summary of the classifica-tions of these sources as determined in Pietsch et al. (2005) aregiven in Table 3. Sources are either classed as “candidates” or“members of” each class in Pietsch et al. (2005), but here theyare grouped together. The hard class contains all the sources withHR2-EHR2 > − . / or HR4 defined, and noother classification (see Pietsch et al. 2005, for the definitions ofhardness ratios HR2, HR3, HR4 and EHR2 and full details).For the 34 sources not in Pietsch et al. (2005) we searchedthe following catalogues for counterparts:(i) X-ray sources: the
Einstein (Trinchieri & Fabbiano1991), ROSAT / PSPC (Supper et al. 1997, 2001) and
Chandra (Williams et al. 2004; Kaaret 2002) catalogues.(ii)
Stellar objects:
USNO-B1 (Monet et al. 2003), 2MASS(Cutri et al. 2003) and the Local Group Survey (Massey et al.2006). http: // / Catalogue / UserGuide xmmcat.html L. Shaw Greening et al.: An X-ray spectral survey of the disc of M31 with XMM-Newton
Table 3.
Summary of classifications of our sources fromPietsch et al. (2005).
Type Numberhard 207foreground star 42AGN / Galaxy 19Supernova remenants 11Globular cluster source 13Supersoft source 2X-ray binary system 1 (iii)
Radio sources:
VLA all sky catalogue(Condon & Kaplan 1998) and catalogue of sources withinM31 (Walterbos et al. 1985).(iv)
Globular cluster candidates: the Bologna catalogue(Galleti et al. 2004) and the catalogue by Kodaira et al. (2004).(v)
Supernova remnant candidates: catalogues byMagnier et al. (1995) and Ford & Jacoby (1978).Only 2 of the 34 sources in this survey are not found inany other catalogue listed above. Eight sources are identifiedin either Supper et al. (1997) or Supper et al. (2001), one ofwhich (source 184) is identified as a variable supernova rem-nant (SNR). Two radio sources were found in Condon & Kaplan(1998) (Sources 184 and 23), both of these are also in theSupper et al. (1997) or Supper et al. (2001) source lists. All theother sources have potential counterparts in the optical cata-logues and are classified as < hard > following the convention ofPietsch et al. (2005).The classification for all 327 sources are given in Table A.1;we distinguish the sources classified in this work by a (1) besidetheir classification.
4. Results
We present a summary of the results of our spectral analysis,with the number of detections and faint sources per field as wellas a breakdown of the best fit models in each field, in Table 4.The quoted luminosity of the faint limit in Table 4 is the luminos-ity of the brightest source with less than 50 source counts. Fulldetails of the source positions, spectral fitting and classification(see Sec. 3.4) of each source are listed in Table A.1.
Table 4 shows that a power law model is the best fit model inthe majority of cases, although Fig. 1 shows a wide range of bestfit photon index. Only four sources with more than 50 sourcecounts have few or no counts above 2keV. These are fit withthe nsa model. Of these four only two sources are best fit withthe nsa model, accordingly these sources are described as su-persoft. Of the three models tested in this survey (see Sec. 3.2)foreground sources would be best fit by a blackbody model; infact 10 of the 27 sources best fit by a blackbody model in thiswork are classified as foreground stars in Pietsch et al. (2005)(see Table A.1).Following the work of Trudolyubov et al. (2006) on the cen-tral region of M31, we investigated the distribution of photonindex for all sources, not just those for which a power lawwas the best fit. Figure 1 shows the distribution of the best fit
Fig. 1.
Distribution of photon index derived from the best fitpower law model for each source, with the exception of very softsources ( Γ > Γ ) to every source. We have com-pared the data from the disc to sources in the central region fromTrudolyubov et al. (2006), who used the same method to derivethe spectral indices except that they have presented a weightedmean of the spectral indices derived from multiple observations.There are 33 disc sources with extremely soft spectra ( Γ > Γ ∼ . Γ ∼
1, a feature which is absentin the central region. While this excess is seen most obviouslyin the full disc sample, it is also seen in each field individually.The excess is suggestive but a KS test does not rule out that bothsamples in Fig. 1 are drawn from the same parent population(KS probability 0.36)There are 23 disc sources with 0 . ≤ Γ ≤ . χ around the best fit photon index was investi-gated for all 23 sources. Five of the seven with large errorswere found to have a very shallow variation in χ . This indi-cates that the best fit Γ is not well defined, we thus excludethese sources from the group with 0 . ≤ Γ ≤ .
2. A pho-ton index of around 1 is expected from magnetically accretingneutron stars (White et al. 1995) and thus indicates the pres-ence of highly magnetic neutron stars in the disc of M31. Sincethe magnetic field of the neutron star is expected to be weakerin LMXBs than HMXBs (Tauris & van den Heuvel 2006), thesesources are strong HMXB candidates - the first such candidatesin M31. The 18 HMXB candidates are given in Table 5; wehave 16 good candidates with small errors and two secondarycandidates with a large 90% confidence interval but a sharplydefined minimum. Table 5 gives astrometrically corrected posi-tions from the source catalogue of Pietsch et al. (2005) whereavailable. For the three HMXB candidates not in the source cat-alogue of Pietsch et al. (2005), we apply the appropriate astro-metric corrections as given by Pietsch et al. (2005) to calculatethe positions quoted in Table 5. For each of the HMXB candi-dates we also give the details of the best fit power law model(n H and Γ ), the luminosity derived from that fit and the V mag-nitude extinction, calculated from the X-ray band absorption viaA v = nH / (1 . × ) cm − , see Predehl & Schmitt (1995). From . Shaw Greening et al.: An X-ray spectral survey of the disc of M31 with XMM-Newton 5 Table 4.
Overview of the source spectral analysis for each field. “Faint” denotes the number of sources with <
50 source counts, inbrackets is the number of sources for which we cannot quote a luminosity. For details on the HMXB candidates see text. The faintlimit is the luminosity below which all sources have less than 50 source counts.
Field Number of sources best fit by Luminosity of faintdetections faint power law blackbody bremsstrahlung nsa HMXB candidates limit, erg s − North 3 82 19 (3) 55 2 5 0 7 8.6 × North 2 57 32 (0) 18 4 3 0 3 1.7 × North 1 80 11 (2) 55 8 6 0 3 5.0 × South 1 71 16 (5) 41 9 4 1 3 7.4 × South 2 45 17 (3) 23 4 0 1 2 9.8 × Table 5.
X-ray properties of the 18 candidate HMXBs with a photon index between 0.8 and 1.2. Coordinates are astrometricallycorrected. The parameters of the best fit power law model are quoted in columns 5 & 6. The symbol f signifies that the absorptionwas fixed to 0 . × H atoms cm − for that field. 90% confidence interval errors are quoted for both the absorption and photonindex. Next we give the luminosity derived from the best fit model, the bracketed numbers are the error in the last significantfigure. The luminosity and its errors are calculated from the 90% confidence interval. We also give the V magnitude absorptionat the distance of M31. The final column indicates the Massey et al. (2006) designation of any optical source within 3.3 ′′ of theastrometrically corrected position. The strong candidates are listed in the top section of the table and the secondary candidates inthe lower section. Field Source RA Dec n H Photon index Luminosity A v OpticalNumber (J2000) (J2000) / H atom cm − / erg s − coincidenceSouth 2 21 0:40:01.50 + . + . − . + . − . + . + . − . + . − . + + . − . + + . + . − . + . − . + . + . − . + . − . + + + . − . + + + . − . + + . − . + + + . − . + . + . − . + . − . + + + . − . + + + . − . + + . − . + + + . − . + + . − . + + + . − . + + . − . + + . − . + the V magnitude extinction it is also possible to calculate theB − V colour excess E(B − V) = A v / ellipse of M31 down to a limiting magnitudeof V = V -6 and 0, as well as both − . < B-V < . − . < V-I < . >
18 and (B − V) < ′′ of the astrometri-cally corrected positions. This search radius is calculated as inSec. 3.4 where, for the astrometrically corrected XMM-Newtonpositions, σ satistical = ′′ and σ systematic = . ′′ . Eight of the 16good HMXB candidates and one of the two secondary candi-dates have counterparts within this search radii in Massey et al.(2006), four of these have the magnitudes and colours that wewould expect for a Be-type star in M31. All potential counter-parts are listed in Table 5.Using the method described below we investigated the pos-sible contamination of this potential HMXB population by back- L. Shaw Greening et al.: An X-ray spectral survey of the disc of M31 with XMM-Newton
Fig. 3.
Cumulative luminosity functions of sources with morethan 50 source counts (solid) and of sources with more than 150source counts (dashed).ground AGN. We find that AGN could make up ∼
60% ofthe total disc population with L X > erg s − . HoweverGiacconi et al. (2001) found that the average AGN spectrum ofsources in the Chandra Deep Field South (CDFS) was softer thanthe sources considered here. Even the faintest (hardest) group ofsources in the CDFS are found to have Γ = . ± . . ≤ Γ ≤ . Figure 2 shows the cumulative luminosity functions (CLFs) ofeach of the disc fields with the 0.3-10 keV luminosity, L X , plot-ted on the x-axis and the number of sources with a luminos-ity higher than L X on the y-axis. The confirmed foreground star(source 182), AGN (source 27) and background galaxy (source112) have been removed from the relevant fields, however wehave not removed any of the 59 sources which are only clas-sified as foreground or background candidates by Pietsch et al.(2005). The change between freely fit and faint sources in eachfield occurs between 5 × erg s − and 1 . × erg s − . Thesource luminosities below this limit have been calculated usingthe conversion factor from the summed faint source spectrum(see Table 2).South 2 and North 2 have the highest luminosity cuto ff s offreely fit sources. This is due to these observations having theshortest good time due to background flaring. These regions alsohave the smallest number of point source detections. South 1and South 2 have two and three sources respectively with lumi-nosities below 1 × erg s − , while the other fields only havesources above this limit. South 1, North 1 and North 3 have sim-ilar numbers of point source detections and the change betweenfreely modelled sources and faint sources occurs at a similar lu-minosity.In Fig. 3 we present the CLF of all the disc sources com-bined, for sources with more than 50 source counts, and com-pare it to the CLF of sources with more than 150 source counts.For both these CLFs we have removed the three sources knownnot to belong to the disc of M31. This comparison is in orderto check the validity of results derived from the spectral fitting of sources with only 50 source counts. Above ∼ erg s − the two functions are almost identical. Using Sherpa , a straightline fit of the CLFs above 10 erg s − in Fig. 3 gives a slope α = . α = . ∼ erg s − is clearly ap-parent in the CLF of sources with more than 150 source counts,hence demonstrating that it is not an artifact of low count ratesource fitting.Previously Williams et al. (2004), using Chandra , found thatthe northern disc had fewer sources above 10 erg s − thanthe southern disc. They found 10 sources with luminosities thisvalue in the southern disc and only 5 in the northern disc, whilesources with luminosities below this value are more evenly dis-tributed, with 12 in the southern disc and 11 in the northern(numbers from Fig. 11, Williams et al. 2004). We find that South1 may be over abundant in bright sources with 11 non glob-ular cluster sources above 10 erg s − , while the other fieldshave somewhat smaller numbers. There are 5 bright non globu-lar cluster sources in North 1, 3 in North 2, 7 in North 3 and 4 inSouth 2. In total we find 15 non globular cluster sources brighterthan 10 erg s − in the southern disc and 15 in the northerndisc. As there are three northern disc fields and two southern theaverage number of bright sources per field in the southern discis slightly larger than in the northern disc; however the di ff er-ence in the number of sources is not as pronounced as that seenby Williams et al. (2004). This di ff erence is consistent with thediscussion below relating to the comparison between using indi-vidual spectral fitting and using a single simple spectral modelas assumed by Williams et al. (2004)We identify the luminosity below which these observationsare incomplete as the luminosity at which we see a break in theCLF of the whole disc, see Fig. 4. This limit is ∼ × erg s − which is in line with limits quoted in Trudolyubov et al. (2002)(detection limit 5 × erg s − , completeness limit ∼ ergs − for the central region, North 1 and North 2). Chandra sur-veys (Kong et al. (2003) (detection limit 10 erg s − , complete-ness limit 10 erg s − ) and Williams et al. (2004) (completenesslimit 4 × erg s − in the disc)) also have similar limits.The CLF of each field was fit individually with a power lawabove and below the completeness break L b = × erg s − .The results are given in Table 6 (columns 2 & 3 entitled “FreelyFit”). The slopes of the disc CLFs above L b are between the val-ues expected for starburst galaxies and for spiral galaxies fromKilgard et al. (2002). Given that we are examining the disc ofa spiral galaxy, this is to be expected. Fitting the CLF of thebulge of M31, Shirey et al. (2001) find a slope of 1 . ± . . ≤ log L X erg s − < .
1, flattening to α = .
43 forlog L X erg s − < .
4. According to the surveys of Colbert et al.(2004) and Kilgard et al. (2002) galaxies with ongoing or recentstar formation show flatter CLFs than elliptical galaxies consist-ing of old populations. Comparing the slope of the bulge CLFfrom Shirey et al. (2001) with those of the disc from this work(see Table 6) show that the CLF of the disc is flatter than that ofthe core. This result is consistent with the fact that there is moreon-going star formation in the disc of M31 than in the core.Kilgard et al. (2002) analysed seven spiral and starburstgalaxies, not including M31, in a
Chandra mini-survey. Theyused an absorbed 5 keV bremsstrahlung emission model to con-vert from count rate to flux for all detected sources. In or-der to make a direct comparison between our work and theresults from Kilgard et al. (2002), we used a 5 keV thermalbremsstrahlung model with fixed photoelectric absorption (n H = http: // cxc.harvard.edu / sherpa / index.html. Shaw Greening et al.: An X-ray spectral survey of the disc of M31 with XMM-Newton 7 Fig. 2.
Cumulative luminosity functions of each of the disc fields. The y-axes range is 0 to 2, except for North 3 where it is 0-2.5.
Table 6.
Field by field comparison of the slopes above and below the break luminsoty (L b ) for the CLFs created from freely fitspectra and the CLFs of luminosities derived from fixed models. L b is set to 10 erg s − , the slopes are for the CLF above andbelow L b . Data for the bulge of M31 comes from Shirey et al. (2001) where the break is 2 . × erg s − . Data Freely Fit Fixed ModelCLF slope above L b CLF slope below L b CLF slope above L b CLF slope below L b North 3 0.7 0.15 0.8 0.4North 2 0.8 0.12 0.8 0.5North 1 0.7 0.13 0.8 0.8South 1 0.7 0.05 1.0 0.2South 2 0.5 0.06 0.6 0.4Bulge 1.8(4) - . × H atom cm − ) to calculate the luminosity of all theM31 disc sources. Figure 5 shows the North 3 CLF obtained inthis way, as well as the freely fit CLF. There are two main di ff er-ences: firstly, fixing the model gave sources which were fainteron the whole than the freely fit sources, and the total luminos-ity of each field was reduced to only 1 − × erg s − ratherthan 4 − × erg s − . The second e ff ect was the changein average slope of the CLF of each of the fields from α ≃ . α ≃ . ff set. A similar finding for NGC 253 is discussed in detail byBarnard et al. (2007a) and Barnard et al. (2008).Figure 4 shows the CLF of all the disc sources (exclud-ing the 3 identified foreground and background objects), withand without globular cluster (GC) sources. It can be seen thatthere is a distinct flattening of the CLF in the range 37 . ≤ log L X / ergs − ≤ . ≤ log L X / ergs − ≤
38, while thecorresponding probability for the sample without GC sourcesis 2.1%. The K-S probability becomes larger if a power law fitfor the full range of luminosities, including the 8 and 3 sources,respectively, that are brighter than 10 erg s − , is considered.Although the KS test remains inconclusive we point out that thereality of the flattening in the CLF is supported by the fact thatit can also be seen in the CLFs of the M31 disc sources de-rived from prescribed models (see Fig. 5), in the higher countrate sources only (see Fig. 3) and in some of the individualfields of M31 (especially North 3, North 1 and South 2, seeFig. 2). As well as in the CLF of M31 sources, it is possiblethat the same feature is also present in the CLFs of the SMC(Shtykovskiy & Gilfanov 2005) and M33 (Grimm et al. 2005)which are both predominantly young populations but have someevidence for a LMXB contribution.This feature could be due to the emission from a mixtureof HMXB and LMXB populations (see Grimm et al. 2002, forwork on the sub-populations of the Milky Way) or possibly dueto a change in the nature of the compact object. Kalogera (2007) L. Shaw Greening et al.: An X-ray spectral survey of the disc of M31 with XMM-Newton
Fig. 4.
Cumulative luminosity function of all source in the discof M31 (solid), compared to the luminosity function of the discwith known globular cluster sources removed (dashed).
Fig. 5.
Cumulative luminosity functions of North 3. The solidline consists of both the freely fit and faint sources from thiswork, while the dashed line is the luminosity of sources de-rived from assuming a bremsstrahlung emission model withk T = ∼ erg s − )to a population with red giant donors (above the dip). This isbecause, for most magnetic braking laws, the mass transfer ratedriven by nuclear expansion of donors (as in red giant donors)is higher than that for mass transfer driven by orbital angularmomentum losses (short period systems with main sequencedonors). We show in Sec 4.3 below that the flattening is not dueto a change in the background AGN CLF. The CLF for the combined disc flattens below 1 × ergs − , while the very faintest sources are around 10 erg s − . Weexpect that there is a significant contribution from backgroundAGN at these faint luminosities.Moretti et al. (2003) consider the AGN contribution in a hard(2-10 keV) and soft (1-2 keV) energy band. We assume a stan-dard AGN spectrum, a power law model with Γ = .
44 (fol-lowing Rosati et al. 2002), to calculate the AGN flux in our 0.3-10 keV band. We calculated the number of background sources
Fig. 6.
Cumulative luminosity functions of the population ofsources in the disc of M31 from this work (solid) and the de-rived AGN background (dashed). Also shown for luminositiesabove 1.4 × erg s − is the CLF of the disc with the derivedbackground contribution subtracted (dot-dash).in each field above the 0.3-10 keV incompleteness limit ofL X = erg s − (corresponding to a 1-2 keV flux limit of 8 . × − erg s − and a 2-10 keV limit of 1 . × − erg s − ). Giventhat the area of each field is 0.20 deg and using Moretti et al.(2003, Eq. 2) we find that there are 26-30 background sourcesabove 10 erg s − in each disc field of M31. The lower limit iscalculated assuming that all the sources visible in the soft bandare also seen in the hard band, the upper limit assumes that noneof the sources seen in the soft band are seen in the hard band.We can then estimate the shape of the CLF intrinsic to theM31 disc by removing the background AGN contribution ac-cording to Moretti et al. (2003). In Fig. 6 we show the observedcomplete disc CLF (Disc), with a total area of 0.98 deg , and thecalculated sum of the hard and soft background contributions per0.98 deg (Background). According to Moretti et al. (2003) thesoft sources do not contribute above ∼ . × erg s − and sothe total background contribution is very close to the number ofsources seen in the hard (2-10 keV) band. The upper limit totalis shown in Fig. 6 as a dashed line. The model shows that the ob-servations are incomplete below a few × . We also show ourestimation of the CLF of sources intrinsic to M31 (Disc CLFwith the Background CLF subtracted) only above the luminosityat which there are more sources in the disc than in the back-ground (1 . × erg s − ). Below this luminosity the completeM31 CLF is dominated by the backgroud contribution, and theincompleteness of the survey is obvious. We note that the flat-tening of the CLF near 10 erg s − is still very prominent in thebackground corrected CLF.
5. Conclusions
We have revisited five archival XMM-Newton observations ofthe disc of M31. These data revealed 335 point detectionsacross the 5 fields constituting 329 discrete point sources. Allthe sources were fit with three spectral models: blackbody,bremsstrahlung and power law and the results of these fits wereexamined.Using only the best fit power law model to each source, weinvestigated the distribution of photon indices of these fits. Thebroad range of photon index seen in Fig. 1 and the di ff erence inthe CLFs seen in Fig. 5 cast doubt on the validity of assuming thesame spectral model for all sources when analysing more distant . Shaw Greening et al.: An X-ray spectral survey of the disc of M31 with XMM-Newton 9 X-ray point source populations. Individual spectral fitting hasidentified the first 18 HMXB candidates in the disc. The HMXBcandidates are all best fit by a power law with a photon index of0.8-1.2 indicating magnetically acreting neutron stars.For the first time X-ray point sources in M31 with as few as50 source counts have been individually spectrally fit, in contrastto previous surveys which have used the same assumed modelfor all sources except the very brightest. This has led us to createthe first CLFs of the M31 disc region created from 240 individ-ually spectrally fit sources shown in Fig. 2. It can be seen thatthe CLFs of the fields are quite similar across the disc of M31and that there are no obvious changes in the CLF slopes withincreasing apparent distance from the core. The CLFs of bothindividual fields (Fig. 2) and the entire disc both with and with-out GC sources (Fig. 4) show a distinct flattening between 37.0 . log L X erg s − . .
5. This flattening could be due to the emis-sion from a mixture of HMXB and LMXB populations or due toa change in the nature of the compact object or the donor star.This prominent flattening in the CLF of M31 sources may alsoappear at a lower statistical significance in the CLFs of severalother galaxies.Each observation contains not only the point sources in M31but also some contamination from foreground and backgroundsources. We have estimated that there are around 20-31 back-ground AGN above 10 erg s − , in each field observed, and findthat above 1 . × erg s − there are few background AGN ac-cording to Moretti et al. (2003). The CLF here is dominated bythe sources intrinsic to the disc of M31 and any foreground in-terlopers. Following the correlations of the PSPC ROSAT surveywith optical catalogues (Supper et al. 2001), we expect 5-10 for-ground objects above 10 erg s − for each XMM-Newton field(Shirey et al. 2001).M31 is a prime target for population surveys because of itsproximity and similarity to our own Galaxy. We have investi-gated the X-ray point sources in the disc of M31 in detail andthis population challenges theoretical models to explain the fea-tures seen in the distribution of sources and in the CLF. Acknowledgements.
We would like to thank the referee, Sergei Trudolyubov forvery helpful comments. We also thank Wolfgang Pietsch and Simon J. Clarkfor useful conversations during this work. LSG acknowledges support from theOpen University. Astronomy research at the Open University is supported by aSTFC rolling grant. JPO acknowledges support from STFC.
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Appendix A:
In this section we give positional and spectral information onall 335 point source detections in five archival XMM-Newtonobservations of the disc of M31. Table A.1 gives the sourcenumbers in order of RA and the positions as returned by thesource detection routines (i.e. no astrometric corrections wereapplied). We also provide details of which camera the sourcespectra or counts are taken from and details of the best fit spec-tral model for each source, including the absorption (n H ), bestfit photon index ( Γ ) or temperature (k T ) depending on whichmodel, and the luminosity derived from that fit. The symbol fsignifies that the absorption was fixed to 0 . × H atom cm − for that source. Note that several of the faint sources displaya very large formal uncertainty in n H . The actualy best fit val-ues were accepted only if they exceeded the Galactic foregroundvalue (n H = . × H atom cm − ). Errors on the absorptionand Γ/ k T are the two sided, non-symmetric errors derived byxspec. The luminosity given is the mean value of the 90% confi-dence interval and hence has symetric errors quoted in brackets.Best fit values are given for all sources with more than 50 sourcecounts; even for cases where the fit implies significant or verylarge error bars. Sources with less than 50 source counts are de-noted with “faint” as their best fit model, these sources are thensummed by field and the parameters of the best fit power lawto the summed spectrum applied to each source. Hence for thefaint sources no absorption or Γ/ k T are given. Finally we give aclassification for each source. These are the classifications andsource number from Pietsch et al. (2005) where the sources ap-pear in that work. For the 34 sources not in Pietsch et al. (2005)as well as source 238 we give our own classifications and eachof these have a next to it. . S h a wG r ee n i ng e t a l . : A n X -r a y s p ec t r a l s u r v e yo f t h e d i s c o f M w it h X MM - N e w t on , O n li n e M a t e r i a l p3 Table A.1.
Position and spectral properties of each source detected in fivearchival XMM-Newton observations of the disc of M31. We give the detectedsource position and detection camera(s) for each source. The best fit model to asource can be faint (less than 50 source counts), pl (power law), bb (blackbody),br (bremsstrahlung), nsa (neutron star atmosphere) or diskbb (disk blackbody).Unless a source is faint we then give the absorption (n H ) and appropriate param-eter (photon index, Γ , or temperature, k T ) of the best fit model. The symbol fsignifies that the absorption was fixed to 0 . × H atom cm − for that source.For all sources we then quote the luminosity for that source derived from themodel parameters with 90% confidence errors in brackets, and finally a classi-fication, either from Pietsch et al. (2005) with the source number, or this work(denoted with a ). Source RA Dec Camera Best Fit n H Γ/ k T Luminosity Classification(J2000) (J2000) Model / cm − keV / erg s − +
40 : 34 : 51 faint - < hard >
12 00 : 38 : 59.9 +
40 : 39 : 11 faint 0.044 < fgstar >
23 00 : 39 : 23.8 +
40 : 29 : 56 mos pl 0.3 + . − . + . − . < hard >
114 00 : 39 : 25.1 +
40 : 37 : 20 faint 0.300 < hard > +
40 : 46 : 47 faint 0.008 < hard >
156 00 : 39 : 29.0 +
40 : 35 : 42 pn & mos pl 0.16 + . − . + . − . / < hard >
187 00 : 39 : 31.6 +
40 : 36 : 16 faint 0.821 < hard >
198 00 : 39 : 36.6 +
40 : 35 : 29 faint 0.767 < hard >
229 00 : 39 : 38.7 +
40 : 47 : 57 pn pl f 0.8 + . − . < hard > +
40 : 35 : 31 pn & mos pl 0.24 + . − . + . − . / < hard > +
40 : 39 : 44 pn bb f 0.21 + . − . < fgstar > +
40 : 44 : 54 pn pl 1.9 + . − . + . − . < hard > +
40 : 34 : 35 faint 0.816 < AGN > +
40 : 35 : 14 pn & mos pl 0.7 + . − . + . − . / < hard > +
40 : 41 : 00 pn & mos nsa 1.07 + . − . + . − . / < fgstar > +
40 : 27 : 26 pn bb 0.26 + . − . + . − . < SNR > +
40 : 31 : 59 pn & mos pl 0.28 + . − . + . − . / < hard > +
40 : 26 : 41 faint 0.202 < hard >
19 00 : 40 : 01.1 +
40 : 25 : 24 pn pl f 1.2 + . − . < hard > +
40 : 33 : 23 pn pl 0.9 + . − . + . − . < hard > . S h a wG r ee n i ng e t a l . : A n X -r a y s p ec t r a l s u r v e yo f t h e d i s c o f M w it h X MM - N e w t on , O n li n e M a t e r i a l p4 Table A.1. continued.
Source RA Dec Camera Best Fit n H Γ/ k T Luminosity Classification(J2000) (J2000) Model / cm − keV / erg s −
21 00 : 40 : 01.6 +
40 : 32 : 43 pn & mos pl 0.4 + . − . + . − . / < hard > +
40 : 24 : 09 faint - < hard > +
40 : 21 : 48 faint - SNR
24 00 : 40 : 07.1 +
40 : 41 : 42 faint 0.783 < hard > +
40 : 31 : 14 pn & mos pl 0.28 + . − . + . − . / < fgstar > +
40 : 47 : 12 faint - < hard > +
40 : 50 : 06 pn pl 0.41 + . − . + . − .
753 (23) AGN5028 00 : 40 : 13.9 +
40 : 35 : 33 pn & mos bb 0.7 + . − . + . − . / < fgstar > +
40 : 51 : 35 faint - < hard >
30 00 : 40 : 14.3 +
40 : 33 : 41 pn & mos pl 0.16 + . − . + . − . / < hard > +
40 : 53 : 07 faint - < hard > +
40 : 50 : 37 pn pl 1.0 + . − . + . − . < hard >
33 00 : 40 : 17.8 +
40 : 32 : 57 pn pl 0.3 + . − . + . − . < hard > +
40 : 48 : 41 pn & mos pl 0.20 + . − . + . − . / < hard >
35 00 : 40 : 20.2 +
40 : 43 : 59 pn & mos pl 0.16 + . − . + . − .
140 (15) /
225 (12) GlC5536 00 : 40 : 20.9 +
40 : 39 : 18 pn & mos pl 0.8 + . − . + − / < hard > +
40 : 36 : 09 pn & mos pl 0.25 + . − . + . − . / < hard > +
40 : 53 : 05 mos bb f 0.20 + . − . < fgstar > +
40 : 29 : 45 pn & mos pl 0.16 + . − . + . − . / < hard > +
40 : 46 : 34 faint 0.407 < hard > +
40 : 37 : 06 pn & mos pl 0.8 + . − . + − / < hard > +
40 : 58 : 34 faint 0.153 < SNR > +
41 : 00 : 45 faint - < hard > +
40 : 49 : 39 pn pl 0.3 + . − . + . − . < hard > +
40 : 40 : 45 faint - < SSS > +
41 : 06 : 10 mos bb 0.6 + . − . + . − . < hard > +
40 : 25 : 47 faint 0.431 < hard > . S h a wG r ee n i ng e t a l . : A n X -r a y s p ec t r a l s u r v e yo f t h e d i s c o f M w it h X MM - N e w t on , O n li n e M a t e r i a l p5 Table A.1. continued.
Source RA Dec Camera Best Fit n H Γ/ k T Luminosity Classification(J2000) (J2000) Model / cm − keV / erg s −
48 00 : 40 : 42.9 +
40 : 32 : 41 pn & mos pl 0.6 + . − . + . − . / < hard > +
40 : 48 : 58 pn & mos pl 0.7 + . − . + . − . / < hard > +
40 : 51 : 37 pn & mos bb f 0.18 + . − . / < hard > +
40 : 29 : 12 faint 0.441 < fgstar > +
40 : 55 : 20 pn & mos pl 0.32 + . − . + . − . / +
40 : 51 : 11 pn pl f 2.7 + . − . < hard > +
40 : 49 : 25 mos br f 0.36 + . − . < hard > +
40 : 30 : 33 pn & mos pl 0.41 + . − . + . − . / < hard > +
41 : 07 : 30 faint 0.495 < hard > +
40 : 36 : 21 faint 0.035 < hard > +
40 : 56 : 38 pn & mos pl 0.29 + . − . + . − . / < fgstar > +
41 : 00 : 26 faint 0.072 < hard > +
40 : 27 : 08 mos bb f 0.49 + . − . < hard > +
40 : 50 : 47 pn pl 0.3 + . − . + . − . < hard > +
40 : 51 : 28 pn & mos pl 0.20 + . − . + . − . / < hard > +
41 : 04 : 52 pn & mos pl 2.9 + . − . + . − . / < hard > +
40 : 54 : 20 mos bb f 0.7 + . − . < hard > +
40 : 51 : 33 faint - < hard > +
40 : 59 : 47 pn & mos pl 0.15 + . − . + . − . / < hard > +
41 : 09 : 05 faint 0.549 < hard >
68 00 : 41 : 15.1 +
41 : 01 : 00 pn & mos br 0.39 + . − . + . − . / < hard > +
41 : 06 : 43 pn & mos pl 0.21 + . − . + . − . / < hard > +
40 : 51 : 58 pn & mos pl 0.13 + . − . + . − . / < fgstar > +
41 : 00 : 09 faint 0.147 < hard > +
41 : 03 : 39 pn pl 0.7 + . − . + . − . < hard > +
41 : 07 : 54 pn & mos pl 0.17 + . − . + . − . / < hard > +
40 : 51 : 11 pn & mos pl f 2.07 + . − . / < hard > . S h a wG r ee n i ng e t a l . : A n X -r a y s p ec t r a l s u r v e yo f t h e d i s c o f M w it h X MM - N e w t on , O n li n e M a t e r i a l p6 Table A.1. continued.
Source RA Dec Camera Best Fit n H Γ/ k T Luminosity Classification(J2000) (J2000) Model / cm − keV / erg s −
75 00 : 41 : 25.6 +
40 : 58 : 44 pn & mos pl 0.5 + . − . + . − . / < hard > +
40 : 53 : 25 pn & mos pl 0.12 + . − . + . − . / < hard > +
40 : 54 : 51 faint 0.615 < hard > +
41 : 02 : 08 pn nsa 0.28 5.96 0.84 (0.84) < hard > +
40 : 59 : 57 pn & mos pl f 2.32 + . − . / < hard > +
41 : 06 : 53 pn & mos pl 0.14 + . − . + . − . / +
41 : 00 : 18 pn & mos pl 0.17 + . − . + . − . / < fgstar > +
41 : 01 : 07 pn & mos bb 1.00 + . − . + . − .
328 (305) /
515 (474) < hard > +
41 : 03 : 33 faint - < AGN > +
41 : 00 : 15 faint - < hard > +
41 : 05 : 05 mos pl 0.17 + . − . + . − . < fgstar > +
40 : 43 : 04 faint 0.456 < SNR >
87 00 : 41 : 48.3 +
41 : 07 : 06 faint 0.525 < hard > +
41 : 01 : 07 mos pl 0.4 + . − . + . − . < hard > +
40 : 54 : 28 pn & mos nsa f 5.22 + . − . / < hard > +
40 : 47 : 09 mos pl 0.5 + . − . + . − . +
40 : 53 : 21 pn & mos pl 0.14 + . − . + . − . / < hard > +
41 : 07 : 24 pn & mos pl f 2.2 + . − . / < SSS > +
40 : 47 : 13 pn & mos pl 0.4 + . − . + . − . / < hard > +
40 : 46 : 06 pn & mos pl 0.1 + . − . + . − . / < hard > +
41 : 02 : 48 mos bb 0.5 + . − . + . − . < GlC > +
41 : 00 : 16 pn pl f 0.8 + . − . < GlC > +
41 : 04 : 36 pn & mos pl 0.17 + . − . + . − . / < hard > +
40 : 50 : 38 pn & mos pl 0.48 + . − . + . − .
288 (17) /
284 (11) < hard > +
41 : 06 : 46 pn bb f 1.8 + . − . < hard > +
40 : 53 : 37 faint 0.010 < hard > +
41 : 01 : 14 pn & mos pl 0.27 + . − . + . − . / . S h a wG r ee n i ng e t a l . : A n X -r a y s p ec t r a l s u r v e yo f t h e d i s c o f M w it h X MM - N e w t on , O n li n e M a t e r i a l p7 Table A.1. continued.
Source RA Dec Camera Best Fit n H Γ/ k T Luminosity Classification(J2000) (J2000) Model / cm − keV / erg s −
102 00 : 42 : 15.8 +
40 : 59 : 59 mos pl 1.6 + . − . + − < hard >
103 00 : 42 : 16.3 +
40 : 48 : 15 pn & mos pl 0.4 + . − . + . − . / < SNR > +
40 : 55 : 52 pn & mos pl 0.13 + . − . + . − . / < hard > +
40 : 52 : 41 pn pl f 3 + − < hard > +
41 : 00 : 23 pn & mos br 0.5 + . − . + . − . / < hard >
107 00 : 42 : 22.0 +
40 : 59 : 23 pn pl 0.19 + . − . + . − . < hard > +
41 : 07 : 35 pn pl f 1.5 + . − . < hard > +
40 : 57 : 20 pn & mos br f 5.6 + . − . / +
40 : 54 : 52 pn pl 0.21 + . − . + . − . < hard > +
41 : 04 : 36 mos bb f 0.9 + . − . < hard > +
41 : 03 : 28 pn pl f 1.78 + . − . +
40 : 57 : 19 pn & mos pl 0.7 + . − . + . − . / < hard > +
40 : 48 : 40 pn & mos pl 3 + − + . − . / < hard > +
40 : 58 : 48 pn & mos pl 0.20 + . − . + . − . / < hard > +
40 : 51 : 50 faint 0.298 Gal315117 00 : 42 : 51.2 +
41 : 32 : 12 mos pl 0.5 + . − . + . − . < hard >
118 00 : 42 : 51.8 +
41 : 31 : 10 mos br 0.23 + . − . + −
411 (14) GlC351119 00 : 42 : 53.4 +
41 : 29 : 54 mos pl 0.13 + . − . + . − . < hard > +
41 : 39 : 13 faint 0.269 < hard > +
41 : 37 : 33 pn bb 0.4 + . − . + . − . < hard > +
41 : 29 : 45 mos pl 0.4 + . − . + . − . < hard > +
41 : 30 : 18 mos pl 0.18 + . − . + . − . +
41 : 38 : 46 pn & mos pl 0.18 + . − . + . − . / < AGN > +
41 : 40 : 24 faint 0.222 < fgstar > +
41 : 35 : 23 pn pl f 2.5 + . − . < hard > +
41 : 46 : 03 pn pl 0.5 + . − . + . − . < hard > +
41 : 32 : 13 pn br f 0.4 0.95 (0.9) < hard > . S h a wG r ee n i ng e t a l . : A n X -r a y s p ec t r a l s u r v e yo f t h e d i s c o f M w it h X MM - N e w t on , O n li n e M a t e r i a l p8 Table A.1. continued.
Source RA Dec Camera Best Fit n H Γ/ k T Luminosity Classification(J2000) (J2000) Model / cm − keV / erg s −
129 00 : 43 : 10.4 +
41 : 38 : 54 pn pl 5 + − + . − . < hard > +
41 : 39 : 16 pn & mos pl 0.4 + . − . + . − . / < hard > +
41 : 43 : 14 pn br 0.23 + . − . + . − . < fgstar > +
41 : 31 : 47 pn & mos pl f 1.8 + . − . / < hard > +
41 : 35 : 56 pn & mos pl f 1.5 + . − . / < hard > +
41 : 36 : 52 pn & mos pl 0.38 + . − . + . − . / < hard > +
41 : 40 : 49 pn & mos pl f 1.9 + . − . / < hard > +
41 : 45 : 50 pn & mos pl 0.8 + . − . + . − . / < hard > +
41 : 33 : 22 pn & mos pl 0.5 + . − . + . − . / < hard > +
41 : 26 : 54 pn & mos bb f 1.33 + . − . / +
41 : 41 : 05 pn & mos pl 1.7 + . − . + . − . / < AGN > +
41 : 42 : 26 pn bb f 0.16 + . − . < fgstar > +
41 : 33 : 11 13060 0.422 < hard > +
41 : 28 : 47 pn & mos pl 0.30 + . − . + . − . / < GlC > +
41 : 36 : 57 pn & mos pl f 1.84 + . − . / +
41 : 27 : 09 pn pl 0.5 + . − . + . − . < hard > +
41 : 38 : 40 mos br f 0.4 + . − . < fgstar > +
41 : 27 : 47 pn & mos bb 0.20 + . − . + . − . / < fgstar > +
41 : 33 : 20 pn & mos pl 0.5 + . − . + . − . / < hard > +
41 : 35 : 34 faint 0.304 < hard > +
41 : 31 : 05 mos pl f 0.9 + . − . < hard > +
41 : 32 : 54 pn pl 0.3 + . − . + − < hard > +
41 : 22 : 04 mos pl 0.20 + . − . + . − . +
41 : 49 : 40 faint - < hard >
153 00 : 43 : 57.5 +
41 : 43 : 48 mos pl 0.5 + . − . + . − . < fgstar > +
41 : 30 : 57 pn & mos pl f 1.63 + . − . / < hard > +
41 : 28 : 03 mos pl f 1.3 + . − . < hard > . S h a wG r ee n i ng e t a l . : A n X -r a y s p ec t r a l s u r v e yo f t h e d i s c o f M w it h X MM - N e w t on , O n li n e M a t e r i a l p9 Table A.1. continued.
Source RA Dec Camera Best Fit n H Γ/ k T Luminosity Classification(J2000) (J2000) Model / cm − keV / erg s −
156 00 : 44 : 01.8 +
41 : 40 : 30 pn pl 0.6 + . − . + . − . < hard > +
41 : 39 : 28 pn & mos pl 0.9 + . − . + . − . / < hard > +
41 : 44 : 24 pn pl 0.6 + . − . + . − . < hard > +
41 : 21 : 28 mos br 7 + − + . − . < AGN > +
41 : 38 : 57 mos pl f 1.0 + . − . < hard > +
41 : 56 : 07 faint 1.020 < hard > +
41 : 33 : 45 pn & mos pl f 3.7 + . − . / < hard > +
41 : 31 : 50 pn & mos pl 0.13 + . − . + . − . / < hard > +
41 : 45 : 13 pn & mos pl f 1.9 + . − . / < hard > +
41 : 56 : 52 faint 1.528 < hard > +
41 : 30 : 59 pn & mos pl 0.9 + . − . + . − . / +
41 : 26 : 29 faint 0.207 < fgstar > +
41 : 50 : 24 faint 0.575 < fgstar > +
41 : 51 : 33 faint 1.202 < hard > +
41 : 32 : 11 mos pl 1.4 + . − . + . − . < hard > +
41 : 34 : 07 pn & mos pl f 2.2 + . − . / < hard > +
41 : 35 : 43 pn & mos pl f 1.1 + . − . / < hard > +
41 : 45 : 07 pn & mos pl f 1.93 + . − . / < hard > +
42 : 00 : 08 pn bb f 0.16 + . − . < fgstar > +
41 : 32 : 01 pn & mos pl 0.20 + . − . + . − . / < hard > +
41 : 36 : 35 pn & mos bb 0.24 + . − . + . − . / < fgstar > +
41 : 30 : 35 pn & mos pl 0.24 + . − . + . − . / < hard > +
41 : 42 : 09 pn br f 0.4 + . − . < hard > +
41 : 54 : 49 faint - < hard >
180 00 : 44 : 30.4 +
41 : 40 : 40 faint 0.399 < hard > +
41 : 23 : 06 mos bb f 0.7 + . − . < hard > +
41 : 25 : 23 pn pl f 2.5 + . − . . S h a wG r ee n i ng e t a l . : A n X -r a y s p ec t r a l s u r v e yo f t h e d i s c o f M w it h X MM - N e w t on , O n li n e M a t e r i a l p10 Table A.1. continued.
Source RA Dec Camera Best Fit n H Γ/ k T Luminosity Classification(J2000) (J2000) Model / cm − keV / erg s −
183 00 : 44 : 33.5 +
42 : 06 : 07 faint 1.240 < hard > +
41 : 25 : 31 faint 0.134 < hard >
185 00 : 44 : 36.8 +
42 : 04 : 36 pn pl 0.3 + . − . + . − . < hard > +
41 : 45 : 15 pn & mos pl 0.16 + . − . + . − . / < AGN > +
41 : 45 : 14 mos pl 0.12 + . − . + . − . < AGN > +
41 : 40 : 09 pn & mos pl f 8 + − / < hard >
189 00 : 44 : 38.7 +
41 : 31 : 47 pn & mos pl 0.6 + . − . + . − . / < hard > +
41 : 53 : 41 pn & mos pl 6 + − + . − . / < hard > +
41 : 26 : 28 pn pl f 3.7 + . − . < hard >
192 00 : 44 : 43.6 +
41 : 46 : 47 faint 1.084 < AGN > ?193 00 : 44 : 44.8 +
41 : 51 : 55 pn & mos pl f 1.6 + . − . / < hard > +
41 : 46 : 45 faint 0.156 < AGN > +
41 : 42 : 22 pn & mos bb f 1.4 + . − . / < hard > +
41 : 29 : 21 faint 0.260 SNR583197 00 : 44 : 47.3 +
41 : 44 : 14 pn & mos pl f 1.0 + . − . / < hard > +
41 : 58 : 13 faint 1.386 < hard > +
41 : 47 : 27 faint 1.465 < hard > +
41 : 47 : 28 pn pl f 2 1.47 (0.97) < hard > +
41 : 29 : 06 pn & mos pl f 3.0 + . − . / +
41 : 27 : 11 pn & mos pl f 1.9 + . − . / < hard >
203 00 : 44 : 51.5 +
41 : 38 : 33 pn pl f 2.1 + . − . < fgstar > +
42 : 02 : 15 faint 0.178 < fgstar > +
41 : 34 : 41 pn & mos pl 0.5 + . − . + . − . / < AGN > +
41 : 59 : 37 pn & mos br 0.17 + . − . + . − . / < fgstar > +
41 : 46 : 23 pn pl f 2.0 + . − . < hard > +
41 : 46 : 21 faint 1.029 < hard > +
41 : 40 : 06 pn bb f 0.8 + − . < hard > . S h a wG r ee n i ng e t a l . : A n X -r a y s p ec t r a l s u r v e yo f t h e d i s c o f M w it h X MM - N e w t on , O n li n e M a t e r i a l p11 Table A.1. continued.
Source RA Dec Camera Best Fit n H Γ/ k T Luminosity Classification(J2000) (J2000) Model / cm − keV / erg s −
210 00 : 45 : 00.5 +
41 : 27 : 04 pn pl 0.5 + . − . + . − . < hard > +
41 : 56 : 09 faint 1.036 < AGN > +
42 : 06 : 19 faint 4.461 < hard > +
42 : 03 : 00 pn pl f 0.6 + . − . < AGN > +
41 : 53 : 56 faint 1.432 < fgstar > +
42 : 02 : 38 mos br f 0.36 + . − . < fgstar > +
41 : 45 : 59 pn & mos pl 0.15 + . − . + . − . / < hard > +
41 : 35 : 30 faint 0.256 < hard >
218 00 : 45 : 13.8 +
41 : 36 : 17 pn & mos br 0.38 + . − . + . − . / +
41 : 50 : 36 pn bb f 0.22 + . − . < hard > +
41 : 39 : 35 pn pl 2 + − + . − . < hard > +
42 : 09 : 08 faint 0.471 < fgstar > +
41 : 51 : 58 pn pl f 0.3 + . − . < hard > +
41 : 53 : 29 faint 1.014 < hard > +
41 : 44 : 30 faint 0.769 < hard > +
41 : 43 : 12 faint 0.925 < hard > +
41 : 56 : 33 pn pl f 0.9 + . − . < hard > +
42 : 00 : 17 pn pl 0.4 + . − . + . − . < hard > +
41 : 46 : 05 faint 1.081 < SNR > +
42 : 01 : 44 pn bb 2 + − + . − . < hard > +
42 : 12 : 48 faint 0.578 < hard > +
41 : 55 : 07 mos pl 1 + − + . − . < hard > +
42 : 10 : 58 pn & mos pl 0.6 + . − . + − / < fgstar > +
42 : 08 : 07 faint 0.422 < hard > +
42 : 17 : 49 mos pl f 0.9 + . − . < hard > +
42 : 20 : 32 pn & mos pl 0.17 + . − . + . − . / < hard > +
42 : 12 : 33 mos pl f 0.9 + . − . < hard > . S h a wG r ee n i ng e t a l . : A n X -r a y s p ec t r a l s u r v e yo f t h e d i s c o f M w it h X MM - N e w t on , O n li n e M a t e r i a l p12 Table A.1. continued.
Source RA Dec Camera Best Fit n H Γ/ k T Luminosity Classification(J2000) (J2000) Model / cm − keV / erg s −
237 00 : 45 : 38.8 +
41 : 56 : 16 faint + − < fgstar > +
42 : 08 : 05 pn & mos diskbb 0.13 + . − . + . − . / < fgstar > +
42 : 08 : 07 pn & mos bb f 0.17 + . − . / < fgstar > +
42 : 23 : 24 pn & mos pl 0.12 + . − . + . − . / < hard > +
42 : 14 : 20 pn pl 0.8 + . − . + . − . < hard > +
42 : 08 : 42 faint 0.771 < hard >
243 00 : 45 : 44.1 +
42 : 08 : 44 faint 0.496 < hard >
244 00 : 45 : 44.8 +
41 : 58 : 58 pn pl 0.33 + . − . + . − . < hard > +
41 : 49 : 33 faint 0.870 < hard > +
41 : 50 : 30 faint 1.236 < fgstar > +
41 : 58 : 34 faint 1.046 < hard >
248 00 : 45 : 51.5 +
42 : 04 : 20 faint 1.020 < hard > +
42 : 16 : 10 pn br f 0.5 + . − . < hard >
250 00 : 45 : 54.7 +
42 : 13 : 11 faint 0.109 < hard >
251 00 : 45 : 55.2 +
41 : 52 : 11 faint 1.238 < hard > +
42 : 12 : 33 pn & mos pl 0.3 + . − . + . − . / < hard > +
41 : 48 : 32 faint 0.793 < hard >
254 00 : 45 : 57.9 +
42 : 26 : 47 pn & mos pl f 2.3 + . − . / < hard > +
42 : 02 : 59 pn pl f 2.0 + . − . < fgstar > +
42 : 04 : 25 pn & mos pl 0.3 + . − . + . − . / < hard > +
42 : 04 : 21 faint 0.602 < hard > +
42 : 10 : 31 pn & mos pl f 0.03 + . − . / < hard > +
42 : 24 : 31 pn & mos pl 0.3 + . − . + . − . / < fgstar > +
42 : 13 : 22 faint 0.284 < hard >
261 00 : 46 : 04.6 +
41 : 49 : 47 faint 0.982 < SNR > +
41 : 51 : 44 faint 1.186 < hard > +
42 : 25 : 52 mos pl 5 + − + . − . < hard > . S h a wG r ee n i ng e t a l . : A n X -r a y s p ec t r a l s u r v e yo f t h e d i s c o f M w it h X MM - N e w t on , O n li n e M a t e r i a l p13 Table A.1. continued.
Source RA Dec Camera Best Fit n H Γ/ k T Luminosity Classification(J2000) (J2000) Model / cm − keV / erg s −
264 00 : 46 : 05.5 +
42 : 20 : 29 pn & mos pl 0.7 + . − . + . − . / < AGN > +
42 : 10 : 53 mos bb 0.3 + . − . + . − . < hard > +
42 : 29 : 39 faint 0.472 < hard > +
42 : 15 : 45 faint 0.221 < hard > +
41 : 59 : 03 pn pl 0.3 + . − . + . − . < hard > +
42 : 08 : 25 pn & mos pl 0.3 + . − . + . − . / < hard > +
42 : 08 : 27 pn pl f 1.4 + . − . < hard > +
42 : 21 : 51 pn & mos pl 0.2 + . − . + . − . / < hard > +
42 : 10 : 26 faint 0.558 < hard > +
41 : 50 : 41 pn pl f 1.8 + . − . < hard > +
42 : 12 : 13 faint 0.261 < hard >
275 00 : 46 : 16.4 +
42 : 21 : 28 pn & mos pl f 1.6 + . − . / < hard > +
42 : 25 : 36 pn & mos pl 0.18 + . − . + . − . / < hard > +
42 : 15 : 54 pn & mos bb f 11 + − / < AGN > +
42 : 14 : 41 pn & mos pl 0.14 + . − . + . − . / < hard > +
42 : 01 : 46 faint 0.812 < hard >
280 00 : 46 : 24.9 +
42 : 04 : 22 pn & mos pl 0.33 + . − . + . − .
89 (6) /
109 (5) < hard >
281 00 : 46 : 25.3 +
42 : 24 : 41 pn & mos pl 0.7 + . − . + . − . / < hard > +
42 : 04 : 22 pn pl 0.22 + . − . + . − . < hard >
283 00 : 46 : 26.9 +
42 : 01 : 50 pn pl 0.12 + . − . + . − .
147 (9) GlC752284 00 : 46 : 27.0 +
42 : 01 : 51 pn & mos pl 0.12 + . − . + . − .
146 (10) /
168 (8) GlC752285 00 : 46 : 30.8 +
42 : 00 : 38 faint 1.441 < hard >
286 00 : 46 : 32.0 +
41 : 51 : 25 faint 1.500 < hard >
287 00 : 46 : 32.4 +
42 : 13 : 50 mos pl 1.5 + . − . + − < hard > +
42 : 17 : 55 pn & mos pl 0.9 + . − . + . − . / < hard > +
42 : 16 : 20 pn & mos br f 0.5 + . − . /
041 (0.35) < fgstar > +
42 : 25 : 20 pn & mos pl 0.25 + . − . + . − . / < fgstar > . S h a wG r ee n i ng e t a l . : A n X -r a y s p ec t r a l s u r v e yo f t h e d i s c o f M w it h X MM - N e w t on , O n li n e M a t e r i a l p14 Table A.1. continued.
Source RA Dec Camera Best Fit n H Γ/ k T Luminosity Classification(J2000) (J2000) Model / cm − keV / erg s −
291 00 : 46 : 40.7 +
41 : 54 : 23 pn br 3 + − + . − . < AGN > +
42 : 20 : 51 faint 0.493 < hard > +
42 : 13 : 37 pn pl 2 + − + . − . < hard > +
42 : 09 : 48 pn & mos pl f 1.1 + . − . / < hard > +
42 : 27 : 18 pn & mos pl f 1.1 + . − . / < hard >
296 00 : 46 : 48.0 +
42 : 08 : 52 pn & mos pl 0.4 + . − . + . − . / < AGN > +
42 : 09 : 30 mos pl f 4.3 + . − . < fgstar > +
42 : 25 : 25 faint 0.238 < hard > +
42 : 19 : 49 pn & mos pl 0.2 + . − . + . − . / < hard > +
42 : 15 : 5 pn & mos pl f 1.8 + . − . / < hard > +
42 : 17 : 10 pn & mos pl 0.3 + . − . + . − . / < hard > +
42 : 19 : 13 pn pl f 0.9 + . − . < hard > +
42 : 10 : 18 pn & mos pl 1.4 + . − . + . − . / < hard > +
42 : 20 : 48 pn & mos pl 0.15 + . − . + . − .
43 (2) /
53 (2) < hard > +
42 : 24 : 13 pn pl f 1.1 + . − . < fgstar > +
42 : 18 : 06 faint 0.282 < hard >
307 00 : 47 : 00.4 +
42 : 21 : 55 pn bb f 0.15 + . − . < fgstar > +
42 : 22 : 46 pn & mos pl f 1.7 + . − . / < hard > +
42 : 18 : 35 pn & mos pl 0.2 + . − . + . − . / < hard > +
42 : 04 : 48 pn & mos pl 0.2 + . − . + . − . / < hard > +
42 : 16 : 47 faint 0.533 < hard > +
42 : 22 : 09 pn & mos pl 0.41 + . − . + . − . / < hard > +
42 : 18 : 10 pn & mos pl 0.6 + . − . + . − . / < hard > +
42 : 24 : 04 pn & mos pl 0.39 + . − . + . − . / < hard > +
42 : 10 : 09 mos bb f 2 + − < hard > +
42 : 18 : 45 mos pl f 1.7 + . − . < hard > +
42 : 16 : 13 pn pl f 2.3 + . − . < hard > . S h a wG r ee n i ng e t a l . : A n X -r a y s p ec t r a l s u r v e yo f t h e d i s c o f M w it h X MM - N e w t on , O n li n e M a t e r i a l p15 Table A.1. continued.
Source RA Dec Camera Best Fit n H Γ/ k T Luminosity Classification(J2000) (J2000) Model / cm − keV / erg s −
318 00 : 47 : 11.3 +
42 : 22 : 22 pn & mos pl 3.4 + . − . + . − . / < hard > +
42 : 20 : 44 pn & mos pl 0.14 + . − . + . − . / < hard > +
42 : 05 : 47 pn & mos br 0.48 + . − . + . − . / < fgstar > +
42 : 08 : 43 faint 0.402 < hard > +
42 : 21 : 16 pn & mos pl 0.19 + . − . + . − . / < hard > +
42 : 21 : 57 pn & mos br 0.96 + . − . + . − .
538 (524) /
605 (593) < fgstar > +
42 : 13 : 46 pn & mos br 2.7 + . − . + . − . / < hard > +
42 : 12 : 01 faint 0.611 < hard >
326 00 : 47 : 35.9 +
42 : 08 : 34 pn & mos pl 0.12 + . − . + . − . / < hard > +
42 : 20 : 21 mos pl 0.11 + . − . + . − . < AGN > +
42 : 22 : 27 mos pl f 1.9 + . − . < hard > +
42 : 11 : 38 pn & mos pl 0.2 + . − . + . − . / < hard > +
42 : 10 : 15 faint 0.618 < hard > +
42 : 12 : 19 faint 0.747 < hard > +
42 : 10 : 58 pn & mos pl 0.23 + . − . + . − . / < hard > +
42 : 18 : 49 faint 0.821 < hard >
334 00 : 47 : 46.9 +
42 : 14 : 22 mos pl 0.7 + . − . + . − . < hard > +
42 : 19 : 33 mos pl 0.21 + . − . + . − . < AGN >>