X-ray Spectra of High-z, Radio

X-ray Spectra of High-z, Radio-quiet Quasars - CSC
X-ray Spectra of High-z, Radio-quiet Quasars
CSC Threads
X-ray Spectra of High-z, Radio-quiet Quasars
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X-ray Spectra of High-z, Radio-quiet Quasars - CSC
Table of Contents
• Science question
• Creating a source list
• Crossmatching the sources against the CSC
• Retrieving CSC source data
♦ Saving search results
♦ Downloading data products
• Analyzing CSC data with CIAO
♦ Fitting CSC source spectra with Sherpa
♦ Plotting CSC source properties with ChIPS
♦ Using CSC save files and data products with CIAO
• History
2
Table of Contents
X-ray Spectra of High-z, Radio-quiet Quasars - CSC
URL: http://cxc.harvard.edu/csc/threads/sci_quasars/
Last modified: 24 November 2010
X-ray Spectra of High-z, Radio-quiet Quasars
CSC Threads
Overview
Last Update: 24 Nov 2010 - updated for CSCview version 1.1.1
Synopsis:
This thread illustrates the use of the Chandra Source Catalog (CSC) in the context of a simple research project:
creating a sample of X-ray spectra of high-redshift, radio-quiet quasars.
Science question
X-ray spectroscopy of high-redshift quasars can help determine whether or not there is evolution in the structure
of quasars and their environment as a function of epoch. Radio-quiet quasars dominate the quasar population, and
have X-ray spectra uncontaminated by components connected to radio emission. In this thread, we illustrate the
use of the CSC in obtaining Chandra X-ray spectra and detailed information on a small set of known sources:
optically selected, high-redshift, radio-quiet quasars (high-z RQQs).
Creating a source list
We begin by compiling a preliminary list of known intermediate- and high-redshift quasars and determine which
objects have suitable Chandra observations. The catalog can be used to filter the list, and to retrieve pre-calculated
spectral data products and source properties for the selected sources.
For our preliminary source list, we choose a lower redshift cutoff of 1.5. We shall require that good optical, radio,
and X-ray data exist, and therefore we apply apparent flux cutoffs in the optical and radio bands.
To create the source list, we query an astronomical database such as Vizier for all quasars/AGN which meet the
following criteria: z>1.5, V<18, and f(5GHz) [=radio]<0.1 Jy. The targets are chosen from high-redshift surveys
based on optical luminosity, and subsequently confirmed as radio-quiet by comparison with radio surveys.
X-ray Spectra of High-z, Radio-quiet Quasars
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X-ray Spectra of High-z, Radio-quiet Quasars - CSC
Figure 1. Vizier query results page
In the this thread we will consider a subset of the quasars found in the search:
• BRI 0103+0032
• BRI 0241-0146
• BRI 0401-1711
• BRI 1033-0327
• BRI 2212-1626
• PSS 1443+2724
Crossmatching the sources against the CSC
We are now ready to query the CSC for X-ray observations of the sources in our list.
To create a Chandra source list matching our optically selected list, we query the catalog by source position via
the CSCview Crossmatch feature. CSCview is a GUI which provides direct access to the contents of the catalog
via user-specified queries.
To begin our query, we first clear any example entries which may be present in the interactive windows of the
Query tab by selecting the "File->New->Empty Form" menu option - or by highlighting these items and selecting
the "-" button next to the appropriate window. (You may choose to have the query form appear empty upon
startup, or populated with an example query with the "Startup Query" option in "Edit->Preferences"; the latter is
the default startup option.) We upload a table containing two columns of data, one each for the RA and Dec.
positions of our sources in decimal degree units, from a TSV format file using the User Table -> Local File
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Creating a source list
X-ray Spectra of High-z, Radio-quiet Quasars - CSC
option of the CSCview crossmatch (VOTable format is also accepted). (Note the caveat associated with the User
Table -> Received Table crossmatch option.) We change the default search radius (Radius parameter) for the
crossmatch query from 3 arcminutes to 1 arcminute, since we expect our sources to be on-axis, and therefore truly
point-like (far off-axis point sources can actually be extended). (Note that the ICRS RA and Dec of each source in
the CSC are determined with an absolute uncertainty that does not exceed 5.0 arcseconds (1σ) for an isolated
point source with at least 30 counts located within 5.0 arcminutes of the optical axis.) Finally, we set the Ra and
Dec crossmatch parameters to the names of the corresponding columns in our input tables, and use the default
values for the Sigma position errors and Obect ID string identifiers for the sources in our list. The optional
crossmatch parameters and their default settings are described below:
• Radius - a single entered radius, or a selected column of radii from the user-input table, in
arcsecs/arcminutes within which to search around each input source position for a CSC source match;
default value is 3 arcminutes.
• Sigma - source position sigma error value(s) to assume for input sources, either a single entered value to
apply to all sources in the list, or a selected column of errors from the user-input table. For example, a
value of 1.0 means that the crossmatch search will assume that each of the source positions in the input
list have associated 1-sigma source position errors. Default setting is no user-input source position errors.
• Object ID - the string to use to identify each source in the user-input list in the returned table of
crossmatch search results, either default 'rowindex' or a selected column from the user-input table; default
will return sources labeled as "row 1", "row 2", and so on.
Figure 2. CSCview crosssmatch query for our preliminary source list
For help with the CSCview crossmatch feature and general CSCview functionality, refer to the CSCview Help
page.
After entering the crossmatch search parameters, we fill the Result Set window of CSCview with the source
properties we would like returned (note that entering a crossmatch query automatically enters the Object ID
associated with our sources into the Result Set window, along with the separation in arcseconds of each returned
source match and a probability measure of the match). In addition to the requisite 'dataset_id' source property for
accessing data products associated with sources returned by the search, we decide to retrieve the per-observation
X-ray source position, broad band energy flux and counts, power-law model fit flux and parameters, and the
True/False value for the "extent" flag. We also select the best estimates of these source properties (CSC "master
source properties") in the event that multiple observations of the source are returned. Finally, we specify in the
Search Criteria window an additional constraint (in addition to the crossmatch) - that the source(s) returned by the
query do not suffer from pileup. The completed query form is shown in Figure 3.
Crossmatching the sources against the CSC
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X-ray Spectra of High-z, Radio-quiet Quasars - CSC
Figure 3. Complete CSCview query, with desired source properties listed in the Result Set
window.
For brief definitions of each source property contained in the catalog, refer to the Master Sources Table and
Source Observations Table; for high-level explanations, see the Catalog Descriptions pages.
We may now retrieve the CSC counterparts to the sources in our preliminary list by sumbitting the crossmatch
query.
Retrieving CSC source data
Saving search results
Downloading data products
Saving search results
Once a CSCview query is submitted, the Results tab opens with a table of search results and a list of associated
data products. In Figure 4, we see the list of all Chandra source matches located within 1 arcminute of each of our
input source positions, with an associated separation in arcseconds, and a probability value describing the
confidence of the match. A probability of 1.0 means that the CSC source returned for the corresponding source in
the input list is an exact match (down to many significant digits in the source position), and a probability of 0.0
means it is very unlikely that it is a true match. We see that multiple source matches are returned for the first and
fifth sources in our input list; the best match of all CSC sources returned for a single source in an input list is the
CSC source with the highest probability value associated with it.
6
Figure 2. CSCview crosssmatch query for our preliminary source list
X-ray Spectra of High-z, Radio-quiet Quasars - CSC
Figure 4. CSCview Results tab, displaying a table of source properties for the sources in the
preliminary list
BRI
BRI
BRI
BRI
BRI
PSS
0103+0032
0241-0146
0401-1711
1033-0327
2212-1626
0059+0003
->
->
->
->
->
->
CXO J010619.2+004823
CXO J024401.8-013403
CXO J040356.6-170322
no CXO match
CXO J221527.2-161133
CXO J005922.6+000301
We notice that a search for the source BRI 1033-0327 (row 2 in our input list) does not return an X-ray object this doesn't necessarily mean that the source was too faint to be observed by Chandra. The source might have
been detected, but it could have failed to satisfy quality assurance (QA) and catalog inclusion (CI) filters in
catalog processing; in particular, the CI filter imposes a source significance threshold. It is also important to keep
in mind that the CSC is constructed from pointed observations; it is not an all-sky catalog, and does not include
sources detected to a uniform depth. The first release of the catalog includes only point and compact sources, with
observed (i.e., un-deconvolved) spatial extents <~30 arcsec; sources larger than this will not be detected with the
current CSC algorithms. In addition, observations of fields containing extended sources have been excluded from
the catalog, or in some cases only a part of the field has been included. More information about the processing
footprint of individual observations contained in the catalog is forthcoming.
As we scroll through the columns of the results table, we note that several cells are empty for some of our sources,
e.g. the power-law model fit parameters and flux (the CSC does not record spectral fit properties for sources with
less than 150 counts). Instead of leaving these spaces blank, we choose to enter vales of "NULL" so that a saved
table of query results will not contain blank spaces for these properties; this is done via the Edit-->Preferences
option in CSCview before saving the file. Then, we can save the table of source properties to a TSV (or VOTable)
format file by clicking Save in the Results tab of CSCview.
The contents of the CSC save file would appear as follows, with a brief description of each selected catalog
column recorded in the header:
unix: cat csc_quasar1_results.tsv
#Column separation
(F9.2) Distance from source to center of cone search
#Column name
(A20)
Source name in the format 'CXO Jhhmmss.s +/- ddmmss'
#Column obsid
(I5)
Observation identifier (obi_source.obsid)
[""]
#Column obi
(I3)
Observation interval number
(obi_source.obi)
Saving search results
(.separation)
(master_source.name)
[meta.id;obs.param]
[""]
[meta.id;obs
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X-ray Spectra of High-z, Radio-quiet Quasars - CSC
#Column ra
(F9.5) Source position, ICRS right ascension
(master_source.ra)
["deg"]
#Column ra_b
(F9.5) Source position, ICRS right ascension; ACIS broad energy band
(obi_source.ra_b)
#Column dec
(F9.5) Source position, ICRS declination
(master_source.dec)
["deg"]
#Column dec_b
(F9.5) Source position, ICRS declination; ACIS broad energy band
(obi_source.dec_b)
#Column livetime
(F9.1) Effective exposure time after applying the good time intervals and the dead
#Column significance
(F7.2) Highest source flux significance across all observations
#Column flux_significance_b
(F9.2) Significance of the source determined from the ratio of the source
#Column nh_gal (G9.4) Galactic neutral Hydrogen column density, N_H(Gal) in the direction of the source d
#Column alpha
(F9.2) Photon index (alpha, defined as F_E ~ 1/E^alpha) of the best power-law model spectr
#Column alpha
(F9.2) Photon index (alpha, defined as F_E ~ E^-alpha) of the best power-law model spectra
#Column flux_powlaw
(E9.3) Net integrated 0.5-10 keV energy flux of the best power-law model spectral
#Column flux_powlaw
(E9.3) Net integrated 0.5-10 keV energy flux of the best power-law model spectral
#Column flux_aper_b
(E9.3) Aperture-corrected net energy flux inferred from the source region aperture
#Column flux_aper_b
(E9.3) Aperture-corrected net energy flux inferred from the source region aperture
#Column src_cnts_aper_b (G9.5) Aperture-corrected net counts inferred from the source region aperture; ACI
#Column extent_flag
(A5)
Deconvolved source extent is inconsistent with a point source at the 90% co
#Column extent_code
(I3)
Deconvolved source extent is inconsistent with a point source at the 90% co
#Column hard_hs (F9.4) Spectral hardness ratio measured between ACIS energy bands 'h' and 's'; hard_hs = (
#Column hard_hs (F9.4) Spectral hardness ratio measured between ACIS energy bands 'h' and 's'; hard_hs = (
#Column posid
(I7)
Internal identifier for a Source Observation
(obi_source.posid)
#Column dataset_id
(I10)
Dataset identifier used to access archive files (obi_source.dataset_id)
separation
name
obsid
obi
ra
ra_b
dec
dec_b
livetime
significance
0.12
CXO J010619.2+004823
2180
0
16.58018
16.58018
0.80650
...
Downloading data products
Level 3 data products, such as images, event lists, and spectra, may be downloaded for each source contained in
the CSC from the Products tab of CSCview (see the Data Products page for the full list of data files provided by
the CSC). At this point, we can download the X-ray PHA spectra, ARF and RMF response files for our sample of
optically selected quasars with corresponding Chandra observations. In the Results tab of CSCview, we select the
row of data in the table of source properties and the desired files from the list of data products, then click
"Search". See the CSCview thread Retrieving Data Products for details on download options.
Figure
8 4. CSCview Results tab, displaying a table of source properties for the sources in thepreliminary list
X-ray Spectra of High-z, Radio-quiet Quasars - CSC
Figure 5. Retrieving the Level 3 X-ray spectrum, ARF, and RMF for our source
The downloaded spectrum (pha3.fits file) may be loaded into Sherpa and visualized:
unix% sherpa
----------------------------------------------------Welcome to Sherpa: CXC's Modeling and Fitting Package
----------------------------------------------------CIAO 4.2 Sherpa version 2 Tuesday, July 6, 2010
sherpa> load_pha("acisf02180_000N001_r0002_pha3.fits")
read ARF file acisf02180_000N001_r0002_arf3.fits
read RMF file acisf02180_000N001_r0002_rmf3.fits
read background file acisf02180_000N001_r0002_pha3.fits
sherpa> calc_data_sum()
26.0
# total counts
sherpa> group_counts(1)
# require minimum of 1 count per bin
sherpa> prefs = get_data_plot_prefs()
sherpa> prefs["yerrorbars"]=0
sherpa> plot_data()
The FITS format PHA file records the low resolution PI spectrum of the events extracted from the source region
and background region, in separate FITS HDUs. A plot of the grouped source spectrum is shown in Figure 5.
Figure 5. Pre-calculated Level 3 source spectrum downloaded from CSC
Figure 5. Retrieving the Level 3 X-ray spectrum, ARF, and RMF for our source
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X-ray Spectra of High-z, Radio-quiet Quasars - CSC
Analyzing CSC data with CIAO
Fitting source spectra with Sherpa
Plotting source properties with ChIPS
Using save files and data products with CIAO
Armed with tables of CSC source data and spectral PHA files, we can begin an analysis of high-z RQQs in the
X-ray regime.
Fitting CSC source spectra with Sherpa
We can use Sherpa to conduct a spectral analysis of the X-ray source regions matching our list of optically
selected quasars; see the Sherpa threads page for a full list of spectral analysis options. Noting that the CSC does
not contain power-law model spectral fit fluxes for sources which, like ours, have <150 counts, we can use Sherpa
to manually derive meaningful spectral fits to our data.
Each Chandra Level=3 PHA file (pha3.fits) available in the Chandra Source Catalog contains both a source and
background spectrum in separate FITS HDUs (CXC Data Model blocks). When a pha3.fits file is loaded into
Sherpa with load_data or load_pha, the background spectrum is automatically recognized and read in as
well, with the same filename as the source spectrum. The resulting source and background Sherpa data sets may
be handled in the usual way in Sherpa.
Here, we fit an absorbed 1-D power law model to one of our PHA spectra downloaded from the CSC, with a
Galactic neutral hydrogen column density fixed at 3e20 cm^-2 and an initial guess of 2 for the power law photon
index:
unix% sherpa
----------------------------------------------------Welcome to Sherpa: CXC's Modeling and Fitting Package
----------------------------------------------------CIAO 4.2 Sherpa version 2 Tuesday, July 6, 2010
sherpa> load_pha("acisf02180_000N001_r0002_pha3.fits")
read ARF file acisf02180_000N001_r0002_arf3.fits
read RMF file acisf02180_000N001_r0002_rmf3.fits
read background file acisf02180_000N001_r0002_pha3.fits
sherpa> group_counts(1)
sherpa>
sherpa>
sherpa>
sherpa>
# require minimum of 1 count per bin
set_source(xsphabs.abs1*powlaw1d.p1)
abs1.nh = .03
freeze(abs1.nh)
p1.gamma = 2
sherpa> show_source()
Model: 1
(xsphabs.abs1 * powlaw1d.p1)
Param
Type
-------abs1.nh
frozen
10
Value
----0.03
Min
--0
Max
Units
------100000 10^22 atoms / cm^2
Figure 5. Pre-calculated Level 3 source spectrum downloaded from CSC
X-ray Spectra of High-z, Radio-quiet Quasars - CSC
p1.gamma
p1.ref
p1.ampl
thawed
frozen
thawed
2
-10
1 -3.40282e+38
1
0
10
3.40282e+38
3.40282e+38
sherpa> set_stat("cstat") # appropriate for low-counts data
sherpa> set_method("neldermead")
sherpa> fit()
Solar Abundance Vector set to angr: Anders E. & Grevesse N. Geochimica et Cosmochimica Acta 53, 19
Cross Section Table set to bcmc: Balucinska-Church and McCammon, 1998
Dataset
= 1
Method
= neldermead
Statistic
= cstat
Initial fit statistic = 6.50845e+06
Final fit statistic
= 28.3459 at function evaluation 295
Data points
= 24
Degrees of freedom
= 22
Probability [Q-value] = 0.1645
Reduced statistic
= 1.28845
Change in statistic
= 6.50842e+06
p1.gamma
1.96741
p1.ampl
7.96099e-06
sherpa> projection()
Dataset
= 1
Confidence Method
= projection
Fitting Method
= neldermead
Statistic
= cstat
projection 1-sigma (68.2689%) bounds:
Param
Best-Fit Lower Bound
------------ ----------p1.gamma
1.90571
-0.304781
p1.ampl
7.56736e-06 -1.40987e-06
Upper Bound
----------0.313394
1.60581e-06
Once we are satisifed with the power-law fit statistic and the model parameter values, we can repeat this
procedure for all of our sources and record pertinent fit information for further analysis. For example, we can
record the power-law photon index values obtained from Sherpa fitting to determine whether it correlates with
quasar redshift.
Plotting CSC source properties with ChIPS
Assuming we have an ASCII file containing a list of quasar redshift values (obtained from optical surveys) and
the corresponding power-law model photon index values we obtained with Sherpa, we can use ChIPS to plot the
two columns against one another:
unix% more z_vs_xray_alpha.dat
#
zem
# ---4.437
4.053
4.236
3.99
4.178
alpha
----1.78
1.33
1.28
1.27
0.75
unix% chips -l python
alpha error
-------0.30
0.36
0.37
0.37
0.41
# or slang
Fitting CSC source spectra with Sherpa
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X-ray Spectra of High-z, Radio-quiet Quasars - CSC
chips> add_curve("z_vs_xray_alpha.dat[cols #1, #2, #3]") # plot z versus alpha
chips> set_curve(["line.style","none"]) # remove line connecting data points
chips> set_plot_xlabel ("quasar redshift")
chips> set_plot_ylabel ("X-ray power-law photon index")
The resulting plot is shown in Figure 6.
Figure 6. Plot of redshift vs. broad band power-law photon index for the sources in our list
ChIPS supports the same file formats as those of the CIAO Data Model, so it can be used to plot the columns of
data in our CSC save file of search results once it has been converted to a CIAO-compatible file (as demonstrated
in the next section). See the ChIPS threads page for a complete list of plotting options.
Using CSC save files and data products with CIAO
To convert a CSC save file of search results to a CIAO-compatible version - e.g., to take advantage of the filtering
and binning options provided by the CIAO Data Model - we can use the Perl script tsv2ciao.pl, which may
be downloaded from the thread Using a CSC Save File in CIAO. Assuming we have concatenated the individual
tables of source properties for each of our sources into a single file (say, q_results.txt) - in which each row
corresponds to a Chandra source and each column a CSC source property - we can proceed as follows:
unix% chmod tsv2ciao.pl 755
# make executable
unix% ./tsv2ciao.pl q_results.txt q_results_out.ciao
unix% ciao
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Plotting CSC source properties with ChIPS
X-ray Spectra of High-z, Radio-quiet Quasars - CSC
CIAO configuration is complete...
CIAO 4.2 Tuesday, July 6, 2010
bindir
: /soft/ciao/bin
ciao%
dmlist q_results_out.ciao cols
-------------------------------------------------------------------------------Columns for Table Block q_results_out.ciao
-------------------------------------------------------------------------------ColNo
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
Name
Unit
name
o.obsid
o.obi
ra
o.ra_b
dec
o.dec_b
o.livetime
significance
o.flux_significance_b
nh_gal
alpha
o.alpha
flux_powlaw
o.flux_powlaw
flux_aper_b
o.flux_aper_b
o.src_cnts_aper_b
extent_flag
o.extent_code
hard_hs
o.hard_hs
o.posid
Type
String[1024]
String[1024]
Real8
Real8
Real8
Real8
Real8
Real8
Real8
Real8
Real8
Real8
String[1024]
String[1024]
String[1024]
String[1024]
Real8
Real8
String[1024]
Real8
Real8
Real8
Real8
Range
-Inf:+Inf
-Inf:+Inf
-Inf:+Inf
-Inf:+Inf
-Inf:+Inf
-Inf:+Inf
-Inf:+Inf
-Inf:+Inf
-Inf:+Inf
-Inf:+Inf
-Inf:+Inf
-Inf:+Inf
-Inf:+Inf
-Inf:+Inf
-Inf:+Inf
-Inf:+Inf
ciao% more q_results_out.ciao
# name o.obsid o.obi
# CXO J010619.2+004823
CXO J005922.6+000301
CXO J024401.8-013403
CXO J040356.6-170322
CXO J221527.2-161133
ra
2180
2179
875
2182
2185
o.ra_b
0
0
0
0
1
dec
o.dec_b
16.58018
14.84444
41.00765
60.98613
333.86372
o.livetime
16.58018
14.84444
41.00765
60.98613
333.86372
significance
o.flux_signi
0.80650
0.80650
0.05034
0.05034
-1.56776
-1.56776
-17.05616
-17.05616
-16.19251
-16.19251
-
The file q_results_out.ciao can easily be manipulated by DM-specific tools in CIAO; for an introduction
to the Data Model syntax used by the CIAO tools, refer to the DM help page. We can now use ChIPS to plot the
columns of data in this file (with the syntax used in the previous section), such as the distribution of source
counts, Galactic NH, fluxes, or other source properties retrieved from the CSC. For example:
unix% ciao
unix% chips
chips> add_curve("q_results_out.ciao[cols #11,#19]") # plot b-band flux significance vs. counts
chips> set_curve(["line.style","none"]) # remove line connecting data points
chips> set_plot_xlabel ("source b-band flux significance")
chips> set_plot_ylabel ("0.5-7.0 keV source counts")
Using CSC save files and data products with CIAO
13
X-ray Spectra of High-z, Radio-quiet Quasars - CSC
Figure 7. Plot of broad band source counts versus significance for the sources in our list
To perform other basic X-ray imaging, timing, or spectral analysis with the data products and save files
downloaded from the CSC, we can follow the relevant CIAO science threads - keeping in mind that many of the
thread steps needed to handle problematic data can be skipped because the CSC data products are uniform and
up-to-date. For more information on the usage of these files, see the page Using L3 Data Products.
For instance, we may be interested in viewing or defining the spatial boundaries of each of our sources in events
images, to search for interesting emission features or even to extract a new PHA spectrum. For this purpose we
could use the CIAO threads Creating Source and Background Files and Using Regions in ds9, which describe
how to define source and corresponding background regions and display them on an events image in ds9.
However, the CSC comes pre-packaged with a file, reg3.fits, which contains both the source and background
extraction region definitions for each source; armed with this file, we can skip most of the steps contained in these
threads and jump right to the punchline:
ciao% dmcopy acisf02180_000N001_r0002_reg3.fits"[SRCREG]" source.reg
ciao% dmcopy acisf02180_000N001_r0002_reg3.fits"[BKGREG]" bkg.reg
ciao% ds9 acisf02180_000N001_evt3.fits -region source.reg -region bkg.reg &
The last command opens an image of the full-field Level 3 events file in ds9, with the regions defined in reg3.fits
displayed (see Figure 8).
14
Figure 7. Plot of broad band source counts versus significance for the sources in our list
X-ray Spectra of High-z, Radio-quiet Quasars - CSC
Figure 8. ds9 image of L3 full-field events file (evt3.fits) with source and background regions
(reg3.fits) overlaid
We can also display the regions on the source region event file, regevt3.fits:
ciao% ds9 acisf02180_000N001_regevt3.fits -region source.reg -region bkg.reg &
Figure 9. ds9 image of L3 source region events file (regevt3.fits) with source and background
regions (reg3.fits) overlaid
After repeating this procedure for all the quasars in our list, we notice that none appear to be inconsistent with
point sources, as suggested by the extent_flag and extent_code values of "FALSE" and "0" in our table of
Figure 8. ds9 image of L3 full-field events file (evt3.fits) with source and background regions (reg3.fits)15overlaid
X-ray Spectra of High-z, Radio-quiet Quasars - CSC
CSCview search results. This seems to confirm what other investigations have found, that high-z RQQs do not
exhibit jets or other extended features in the X-ray regime.
This thread covers just a few examples of the many uses of CSC data products and source properties in
multi-faceted, high-level scientific investigations of point sources like high-z RQQs in the X-ray regime.
History
12 Feb 2009 original version
21 May 2009 updated for CSCview version 1.0.2
11 Aug 2010 updated for CSCview version 1.1
24 Nov 2010 updated for CSCview version 1.1.1
URL: http://cxc.harvard.edu/csc/threads/sci_quasars/
Last modified: 24 November 2010
9. ds9 image
16 of L3 source region events file (regevt3.fits) with source and backgroundregions (reg3.fits) overlaid