PhD Thesis (PDF) - Department of Astronomy - University of Virginia

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2.2 Observation and Data Reduction NGC 4365 was observed on 2001 June 2–3 with a live exposure of 40,429 s, while NGC 4382 was observed on 2001 May 29–30 for 39,749 s. Both galaxies were observed with the ACIS-235678 chips operated at a temperature of −120 ◦ C and with a frame time of 3.2 s. We determined the pointings so that the entire galaxy was located on the S3 chip and so that the center of each galaxy was not on a node boundary of the chip. Although a number of serendipitous sources were seen on the other chips, the analysis of both galaxies in this chapter is based on data from the S3 chip alone. The data were telemetered in Faint mode, and only events with ASCA grades of 0, 2, 3, 4, and 6 were included. Photon energies were determined using the gain file acisD2000-08-12gainN0003.fits. We excluded bad pixels, bad columns, and columns adjacent to bad columns or chip node boundaries. Chandra is known to encounter periods of high background (“background flares”), which especially affect the backside-illuminated S1 and S3 chips. 1 We determined the background count rate for each galaxy, using the S1 chip to avoid the enhanced flux due to the galaxy on the S3 chip. For both NGC 4365 and NGC 4382, no background flares were seen. The backgrounds for extended regions were taken from the deep blank sky backgrounds compiled by Maxim Markevitch 3 , and were adjusted to the aspect histories of our observations using his MAKE ACISBG program 3 The normalization of the background was increased very slightly to match the 5–10 keV count rate of the blank-sky background with a galaxy emission-free region of each galaxy on the S3 chip. We included the “background” due to the readout artifact in ACIS using his MAKE READOUT BG program 3 . On the S3 image of NGC 4365, there were two X-ray sources with positions that 1 See http://cxc.harvard.edu/contrib/maxim/acisbg/. 16
agreed with positions from the USNO-A2.0 (Monet et al. 1998) or the Two Micron All Sky Survey (2MASS; Cutri et al. 2001) catalogs. Source 98 in Table 2.1, an X-ray source near the edge of the field where the Chandra point-spread-function (PSF) is quite broad and the X-ray position is uncertain, corresponded to USNO- A2.0 0900−07143676. For this source, the optical and X-ray positions agree to within ∼0. ′′ 4. The second possible optical identification is between the optical nucleus of NGC 4365 itself and source 1 in Table 2.1. Unfortunately, the central region of this galaxy is crowded with sources, and it is uncertain whether the source closest to the nucleus is, in fact, an active galactic nucleus (AGN), a nearly coincident X-ray binary, or a combination of sources. Confusion limits the accuracy with which the positions of sources near the center of NGC 4365 can be determined. In the absence of more direct evidence, we will assume that the positions in NGC 4365 are accurate to 1 ′′ . In NGC 4382, there were two X-ray sources with optical identifications and positions from the Tycho-2 catalog (Høg et al. 2000), the 2MASS catalog, and/or the USNO-A2.0 optical catalog. The first source, source 38 in Table 2.2, corresponds to J1225+182, a z = 1.19 quasar (Knezek & Bregman 1998), and is the brightest X-ray source in the S3 field. The second source, which was just below the detection threshold for inclusion in Table 2.2, corresponds to BD +18 ◦ 2609, a G5 star with a proper motion of ∼90 mas yr −1 (Høg et al. 1998). The X-ray positions agreed with the optical positions to better than 0. ′′ 4 in both cases with no evidence for a systematic offset. We believe that the X-ray positions for NGC 4382 are generally accurate to ∼0. ′′ 5. We performed initial data reduction and some of the data analysis using the Chan- dra analysis package CIAO 2 . We extracted spectra using the CALCRMF 3 software 2 See http://asc.harvard.edu/ciao/. 3 See http://asc.harvard.edu/cont-soft/software/. 17
Page 1 and 2: LOW-MASS X-RAY BINARIES, DIFFUSE GA
Page 3 and 4: smaller GCs are more likely to cont
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Page 7 and 8: her room (my apologies to her offic
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Page 11 and 12: Table of contents Abstract ii Ackno
Page 13 and 14: 5.2.1 Chandra X-ray Observatory . .
Page 15 and 16: List of Figures 1.1 Hubble Tuning F
Page 17 and 18: List of Tables 1.1 Galactic Low-Mas
Page 19 and 20: Chapter 1 General Introduction 1.1
Page 21 and 22: Fig. 1.1.— Hubble Tuning Fork, co
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Page 31 and 32: Chapter 2 Chandra Observations of L
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Page 49 and 50: log N(>L) 2.0 1.5 1.0 0.5 0.0 NGC 4
Page 51 and 52: luminosity function for luminositie
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Page 55 and 56: 2.4.5 Variability We searched for v
Page 57 and 58: Number 10 8 6 4 2 NGC 4365 Optical
Page 59 and 60: LMXBs has an effective radius of 12
Page 61 and 62: component (“MEKAL”) was used fo
Page 63 and 64: Table 2.4. X-ray Spectral Fits of N
Page 65 and 66: Fig. 2.9.— Top panels: Cumulative
Page 67 and 68: we extended the spectrum down to 0.
Page 69 and 70: We also examined whether the unreso
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02:00.0 03:00.0 04:00.0 05:00.0 06:
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Table 3.1. Discrete X-ray Sources i
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Table 3.1—Continued d a Count Rat
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We also attempted detections in mul
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sociated with extended X-ray or opt
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Fig. 3.3.— Histogram of the obser
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chip. The number of ULX candidates
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these luminosities among previously
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to 2-6 keV. Since the 6-10 keV rang
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absorption and varying power-law in
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counts occur within ∼ 4 ks. Sourc
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log I X (counts/sec/arcmin 2 ) 0.5
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tion), and βouter = 0.36 +0.01 −
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the east and northeast of NGC 1600.
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group, we assumed that they were at
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the group gas than we calculate fro
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04:55 -5:05:00 05 -5:05:10 15 -5:05
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for the spectrum: “Field” impli
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90% confidence level errors. Bracke
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we adopted the power-law model as o
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sources could be a non-trivial sour
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jection to include the emission fro
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Fig. 3.13.— Estimated gas and gra
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ackground source population cannot
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NGC 1600 that has a small spatial s
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(HMXBs). LMC X-4, an HMXB pulsar, h
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searched for the shortest time tn o
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with NGC 4697. Columns (1)-(4) list
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duration, ∆tflat, beginning at a
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the uncertainties quoted do not inc
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to persistent rate for short flares
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Chapter 5 Multi-Epoch Chandra X-ray
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the field, these different populati
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luminous (MB < −20) elliptical (E
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Although Chandra is known to encoun
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42:00.0 44:00.0 46:00.0 48:00.0 -5:
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Fig. 5.3.— Adaptively smoothed Ch
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1 × 10 −5 count s −1 arcsec
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Table 5.1—Continued Source R.A. D
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source list against which to regist
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ate from Observation 0784 alone (Pa
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Table 5.2. : Optical Properties of
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actually be an AGN. Sources 79, 80,
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two potential GC counterparts. We l
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Table 5.3—Continued X-ray Source
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Fig. 5.6.— Color (G475−Z850) -
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mass segregation of GCs with the sa
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Table 5.4. Fits to the Expected Num
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dependence are allowed to vary. Var
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NGC 4697 to convert the observed so
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Table 5.6—Continued Source LA LB
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Table 5.6—Continued Source LA LB
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Table 5.7. Combined Luminosities &
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Table 5.7—Continued Source Not De
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Fig. 5.8.— Cumulative luminosity
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LF, there are enough datapoints tha
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Fig. 5.10.— Cumulative luminosity
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Fig. 5.11.— Merged luminosities (
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Fig. 5.12.— X-ray color-color dia
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5.9 Spectral Analysis We performed
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some data loss, it allows for direc
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for 2 dof and the f-test indicates
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ple to LMXBs interior to that semi-
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est-fit (χ 2 = 56.4 for 65 dof) by
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5.10.1 Intraobservation Variability
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Fig. 5.14.— Binned lightcurve usi
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Table 5.10. Possible Flaring Source
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Fig. 5.16.— Cumulative lightcurve
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pairs of observations. In Figure 5.
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Table 5.11—Continued Source PL,AB
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Fig. 5.17.— Percentage of Analysi
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dofs and the number of combinations
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Table 5.12—Continued Source Obs.S
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of states as transient candidates.
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Long-Term Hardness Ratio Variabilit
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In the final observation, there wer
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limits). The 0.3-10 keV X-ray lumin
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atio is expected only from the most
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eak (Kim et al. 2006a). We find mar
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LMXBs in Galactic GCs (Heinke et al
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in the field of the Milky Way and a
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6.2 Sample 6.2.1 Galaxy Sample Tabl
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Table 6.2. Properties of Chandra Ob
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identification of point sources, AC
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the QE degradation in the ACIS dete
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Table 6.3—Continued Galaxy NX LX,
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The positions of the GCs were used
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Fig. 6.2.— Scatter plot of GC gal
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Fig. 6.3.— Scatter plot of estima
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Fig. 6.5.— Scatter plot of estima
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isophote from the galaxy optical su
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6.3.1 Luminosity and Mass Prior obs
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compare their χ 2 fits to test whi
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GCs without LMXBs; however, there a
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following dependence on GC properti
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of this probability with individual
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Fig. 6.9.— Identical to Figure 6.
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We used the indices from our best-f
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(20.3 for half-mass radius, both wi
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most are steeper than Z ∼0.4 . Ei
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Fig. 6.11.— (Left:) Two-dimension
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differently by the properties of th
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dependent IMF (Grindlay 1987), or e
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a 1.4M⊙ neutron star (NS). They s
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equivalent to a dependence on the b
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variability timescale, but it is no
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7.2.1 X-ray Properties of the GC-LM
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of the metallicity dependence. As i
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Appendix A Encounter Rate Parameter
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Fig. A.1.— Dimensionless quantity
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and four; these positions do not in
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Table B.1—Continued RA Dec. d GC
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Table B.2. Optical Properties of Gl
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investigations into improving the h
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C.4 Sivakoff Signature Soy Sauce Sk
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Blanton, E. L., Sarazin, C. L., & I
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Frogel, J. A., Persson, S. E., Matt
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Johnston, H. M. & Verbunt, F. 1996,
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Makishima, K. et al. 2000, ApJ, 535
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Porter, A. C. 1993, PASP, 105, 1250
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Verner, D. A., Ferland, G. J., Kori
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