International Journal of Application or Innovation in Engineering & Management (IJAIEM)
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Volume 3, Issue 5, May 2014
ISSN 2319 - 4847
Study and Analysis of Absorption
Spectra of Quasars
Bushra Q. AL-Abudi1 and Nuha S. Fouad 2
1,2
University of Baghdad, College of Science, Department of Astronomy and Space,
Baghdad-Iraq
ABSTRACT
A quasi-stellar radio source (quasar) is a very energetic and distant active galactic nucleus. Quasars are extremely luminous and
were first identified as being high red shift sources of electromagnetic energy, including radio waves and visible light, that were
point-like, similar to stars, rather than extended sources similar to galaxies. The simplest way to explain the quasar's red shifts is
to assume that they are extremely distant bodies that follow Hubble's law. In this paper, eight single and four double quasars have
been detected from SDSS .The single quasars are: SDSS J100120.82+555349.8, SDSS J095918.70+020951.5 ,SDSS
J093857.01+412821.2 , SDSS J141647.21+521115.5, SDSS J141030.62+511113.8 , SDSS J005006.35-005319.2 ,SDSS J000552.33000655.6 and SDSS J222851.23+011432.3 ,the double quasars are SDSS J115518.29+193942.2, SDSS J162026.14+120342.0,
SDSS J133907.13+131039.6 and J125418.94+223536.5. For both types quasars , chemical composition are determined and the
redshift are measured from the absorption spectra, it found that the single quasars spans a redshift range of 0.335 ≤ z ≤ 6.47. the;
and double quasars spans a redshift of 1.01 ≤ z ≤ 3.64. Applying Hubble's law to these values of redshift, some features of
absorption line of quasars are measured and analyzed.
Key words: Quasar, Absorption line Spectra, single Quasar; Double Quasars
1. INTRODUCTION
Quasars – growing supermassive black holes in the centers of massive galaxies – are the subset of active galactic nuclei
(AGNs) that constitute the most luminous objects in the universe. They radiate substantial power across much of the
electromagnetic spectrum, with the source of radiation in each frequency regime originating from a different location with
respect to the supermassive black hole. The shape of a quasar’s spectral energy distribution (SED) can reveal much about
the structure of the black hole-accretion disk system[1].Quasars were observed during the first half of the 20th century as
radio-sources, but their nature remained unclear for decades. In the late 50s, radio observations revealed that these sources
were characterized by very small angular sizes: they were star-like objects, or quasi stellar radio sources, later contracted
into quasars. The optical counter-parts of some of these radio sources were observed for the first time in the 60s. Their starlike nature was quickly contradicted by their atypical spectral properties. By 1974, the spectra of over two hundred quasars
had been analyzed, and all of them having very large redshifts. The simplest way to explain the quasar´s redshifts is to
assume that they are extremely distant bodies that follow Hubble´s law; in such a way that they are the most distant objects
known. Moreover, if the redshifts of quasars are caused by the expansion of the Universe, they are very luminous bodies
indeed [2, 3]. The quasar absorption lines are crucial to our understanding of the Universe since the absorption lines
provide a wealth of information on the gaseous Universe from high redshift to present day. The absorption lines can also
allow us to probe them metallicity and ionization state of the gas. Owing to the advent of large spectroscopic surveys such
as the Sloan Digital Sky Survey (SDSS), tens of thousands of quasar absorption lines can be identified [4].
In this paper, we will study and analysis the absorption spectra of single and double quasars. This paper is organized as
follows. Section 2 presents the features of absorption lines spectra. For each quasar; chemical composition were determined
and features of absorption line spectra were measured and analyzed in section 3. .Section 4 is devoted to conclusions.
2. The REDSHIFTS and FEATURES of ABSORPTION LINE SPECTRA
The redshift of a quasar is usually denoted by the letter z; that is to say [5].
z

0
where  is the shift in wavelength of a spectral line, and
(1)
0 is the wavelength that line had when it left the quasar. The
redshifts can also be expressed as a velocity by means of the Doppler shift formula. However, if the velocity is small
compared to the velocity of light, the following simple form of that formula is normally used.
v
Volume 3, Issue 5, May 2014

c
0
(2)
Page 49
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Volume 3, Issue 5, May 2014
  v
0
c
ISSN 2319 - 4847
(3)
where v is the velocity, and c the velocity of light. If formula (2) is converted for the explicit calculation of the redshift Δ
formula (3), we can recognize that at a given velocity, the amount of the shift Δ is proportional to the rest wavelength 0 of
the corresponding spectral line .The classical method to estimate the distance D is based here on the Hubble’s law [6].
(4)
v  c  z  H (t)  D
Where Hubble parameter H(t) is ≈ 73 km s-1 Mpc-1
By converting of formula (4), we get the distance D in (Mpc)
D
c z
H (t)
(5)
Formula (5) also expresses that the distance D increases proportional to the Redshift z. Given that the quasars have very
large redshifts; showing that these objects are moving at relativistic recession velocities; it is necessary to use the exact
formula for the relativistic Doppler shift [6].
1
v 2
 (1  c )

1
 (1  v ) 12
c
(6)
On the other hand, there is another relativistic transformation equation for the volume of the material bodies. Since the
transverse dimensions do not change because of the motion, the volume V of a body decreases according to the following
formula [6].
V  V0 1 
v2
(7)
c2
Where Vo is the proper volume of the body.
It is well known from Optics that the ratio of the image size q, to the object size p is what is called the magnification M; so
that, M=q/p. According to the relativistic transformation equation 7, it could be considered that V is the volume image, and
Vo is the volume object; in such a way that [6].
M  1
v2
c2
And also we can calculate Redshift as lookback Time from the following equation [6].
tn
t
(1  z ) 3
2
Where tn  13.73 Gyr
(8)
(9)
(i) Also from Redshift we can determine the Post-recombination Density nH using the following equation [6].
nH  1.6 x10-7 (1+z)3 Cm-3
(10)
At recombination (z ~1000): nH ~ 200 cm-3, at reionization (z ~ 7): nH ~ 10-4 cm-3 . Also from Redshift we can determine
the Atomic Hydrogen Abundance X(H) using the following equation [6].
X(H) = 4Χ108 (1+z)3 << 1
(11)
Gunn and Peterson (GP) calculate the observed absorption optical depth from Redshift of Quasar as following equation [6].
ƮGP ≈ 2.6Χ104 X(H) (1+z)3/2
(12)
In this work, We selected eight single quasars and four double quasars from the Sloan Digital Sky Survey (SDSS) to
measure the Redshift of quasars [7] .
3. SPECTRAL ANALYSIS of SINGLE QUASARS
Eight single quasars have been detected from SDSS and found Object ID (objID), Right ascension (Ra) and
Declination (Dec) as shown in table 1. Figures 1-8 show the absorption spectrum lines of the eight single quasars.
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Volume 3, Issue 5, May 2014
Table 1: Object ID , Right ascension , and Declination
Quasar Name
objID
SDSS J100120.82+555349.8
1237658304350257268
SDSS J095918.70+020951.5
1237651753997107470
SDSS J093857.01+412821.2
1237657873256677409
SDSS J141647.21+521115.5
1237659120933077046
SDSS J141030.62+511113.8
SDSS J005006.35-005319.2
SDSS J000552.33-000655.6
SDSS J222851.23+011432.3
1237659131670626499
1237657189836980651
1237657190905873463
1237678595933012413,
ISSN 2319 - 4847
for Selected Single Quasars
Ra
Dec
150.33678577
55.8971917
149.82793113
2.16430995
144.73756498
41.47257299
214.19674395
52.18764298
212.62759242
12.52645863
1.46805
337.21346871
51.18717501
-0.88869374
-0.11546
1.24230848
Fig.1: Absorption Spectrum line of Quasar SDSS J100120.82+555349.8
Fig.2: Absorption Spectrum line of Quasar SDSS J095918.70+020951.5
Fig3: Absorption Spectrum of Quasar SDSS J093857.01+412821.2
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Fig.4: Absorption Spectrum of Quasar SDSS J141647.21+521115.5
Fig.5: Absorption Spectrum of Quasar SDSS J141030.62+511113.8
Fig.6: Absorption Spectrum line of Quasar SDSS J005006.35-005319.2
Fig.7: Absorption Spectrum line of Quasar SDSS J000552.33-000655.6
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Fig8: Absorption Spectrum line of Quasar SDSS J222851.23+011432.3
We matching the wavelengths of the absorption lines in the spectrum λobs (Å ) of quasars at a value of flux F(λ), with those
observed from the pure source in the laboratory λrest (Å) [7] Tables 2-9 reflects the extrapolated chemical elements for these
single Quasars. By applying the equations which are mentioned previously, we found the features measured from absorption
spectra as illustrated in Tables 10-17. The relationship between the optical depths as a function of different values of
redshift is shown in figure9. The linear relationship between Recession velocities as a function of distance is shown in
figure 10. The slope determines the value of the Hubble constant. By drawing the relationship between the Look back
times as a function of the redshift for different quasars as shown in figure 11, it clear that whenever the redshift is less
whenever the value of look back time is higher.
Table 2: The chemical composition of Quasar SDSS J100120.82+555349.8
Chemical Element
F(λ)
λobs (Å)
λrest (Å)
O II
65.82
4975
3728.8
Ne II
59.7832
5162.5
3868.7
HƔ
57.6171
5800
4840.48
O III
58.653
6725
5006.8
Table 3: The chemical composition of Quasar SDSS J095918.70+020951.5
Chemical Element
F(λ)
obs. Å
rest Å
C III
6.9331
4100.89
1909
Mg
5.18
6036.46
2851.6
O II
6.5909
8040.93
3728.8
HƔ
4.66
8842.72
4101.75
Ne II
3.7
8354.13
3868
Table4: The chemical composition of Quasar SDSS J093857.01+412821.2
Chemical Elements
F(λ)
obs
Rest
Å
Å
C IV
183.32
4550.949
1550.77
He II
118.8148
4838.77
1640.5
C III
113.646
5633.4
1909
Mg
75.99
8280.111
2851.6
Table 5: The chemical composition of Quasar SDSS J141647.21+521115.5
Chemical Element
F(λ)
obs
Rest
Å
Å
Lyα
63.39
3831.25
1215.67
C IV
C III
Mg
Volume 3, Issue 5, May 2014
25.463
1
15.816
5
11.905
4875
1550.77
6012.5
1909
8831.25
2851.6
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Table 6: The chemical composition of Quasar SDSS J141030.62+511113.8
Chemical Element
F(λ)
Lyα
33.77
obs
Å
5213.4
rest
Å
1215.67
C IV
17.54
6559.2
1550.77
C III
23.81
8046.36
1909
Table7: The chemical composition of Quasar SDSS J005006.35-005319.2
Chemical Element
F(λ)
Lyα
6.5077
obs
Å
6446.927
Rest
Å
1215.67
C IV
3.5232
8155.307
1550.77
He II
3.4374
8579.329
1640.5
Table 8: The chemical composition of Quasar SDSS J000552.33-000655.6
Chemical Element
F(λ)
obs
Rest
Å
Å
HeI
Lyα
S IV+OIV
2.988
6.5549
2.1964
3797.659
8729.431
10348.94
537.029
1215.67
1507.93
Table 9: The chemical composition of Quasar SDSS J222851.23+011432.3
Chemical Element
F(λ)
obs
Rest
Å
Å
HeI
NI
Lyα
65.6089
207.97
22.7273
4369.49
6705.02
8978.77
584.33
885.67
1215.67
Table10: The features measured of absorption line of quasar SDSS J100120.82+555349.8
Z
Z
V(Km/Sec)
D(Mpc)
M
T(Gyr)
n(H)
X(H)
Relative
0.334
100260
2005.2
0.945
8.909
0.415
3.80 x10-7
9.50x10-8
-7
0.3344
100320
2006.4
0.942
8.906
0.416
3.801x10
9.50 x10-8
0.1982
59460
1189.2
0.980
10.647
0.222
2.75 x10-7
9.88 x10-8
0.3432
102960
2059.2
0.939
8.820
0.430
3.877 x10-7
9.7 x10-8
Line
O II
Ne II
HƔ
O III
Average
0.3025
90750
1815
0.951
9.321
0.371
3.80 x10-7
Ʈ(GP)
0.003
0.003
0.002
0.003
9.64 x10-8
0.003
Table 11: The features measured of absorption line of Quasar SDSS J095918.70+020951.5
Line
Z
C III
Mg
O II
HƔ
Ne II
1.148
1.116
1.156
1.155
1.159
V (km/
sec)
344400
335070
346920
346740
347940
Average
1.147
344214
D(Mpc)
M
T(Gyr)
Z Relative
n(H) (cm-3)
X(H)
Ʈ(GP)
6888
6701.4
6938.4
6934.8
6958.8
0.564
0.497
0.580
0.579
0.587
4.360
4.457
4.335
4.337
4.325
2.809
3.255
2.713
2.719
2.676
1.586X 10-6
1.517 X10-6
1.604 X10-6
1.603 X10-6
1.612 X10-6
3.965X 10-7
3.794X 10-7
4.011 X10-7
4.007x X10-7
4.030 X10-7
0.032
0.030
0.033
0.033
0.033
6884.28
0.561
4.363
2.834
1.584 X10-6
3.961 X10-7
0.032
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Table 12: The features measured of absorption line of Quasar SDSS J093857.01+412812.2
Line
Z
V (Km/
Sec)
D(Mpc)
M
T(Gyr)
Z
Relative
n(H) (cm-3)
X(H)
C IV
1.934
58038
11607.6
1.656
2.731
0.772
4.043X 10-6
1.010 X10-6
0.132
-6
-6
Ʈ(GP)
He II
C III
1.949
1.951
58488
58530
11697.6
11706
1.673
1.675
2.710
2.708
0.762
0.761
4.105 X10
4.111 X10-6
1.026 X10
1.027 X10-6
0.135
0.135
Mg
1.903
57111
11422.2
1.619
2.774
0.792
3.9171X10-6
0.979 X10-6
0.126
0.772
-6
-6
0.132
Average
1.934
580417.5
11608.35
1.656
2.731
4.044X 10
1.011X 10
Lyα
C IV
Table13: The features measured of absorption line of Quasar SDSS J141647.21+521115.5
Z
V
D(Mpc)
X(H)
Z
T(Gyr)
n(H) (cm-3)
(Km/Sec)
M
Relative
2.151
645480
12909.6
1.905
2.454
0.654
5.008 X10-6 1.252X10-6
2.143
643080
12861.6
1.896
2.463
0.658
4.970 X10-6 1.242 X10-6
C III
2.149
Line
Mg
2.096
Average
2.135
644880
629070
640627.5
12897.6
12581.4
12812.55
1.902
1.843
1.886
2.456
2.519
2.473
Ʈ(GP)
0.182
0.180
0.655
4.998 X10-6
1.249 X10-6
0.181
0.680
-6
-6
0.168
-6
0.178
0.662
4.752 X10
-6
4.932 X10
1.188 X10
1.232X10
Table 14: The features measured of absorption line of Quasar SDSS J141030.62+511113.8
Line
Z
V(Km/Sec)
D(Mpc)
M
T(Gyr)
Lyα
C IV
C III
Average
3.288
3.229
3.215
3.244
986550
968880
964500
973310
19731
19377.6
19290
19466.2
3.132
3.070
3.055
3.086
1.546
1.5784
1.5866
1.570333
Z
Relative
0.3689
0.377
0.379
0.375
n(H) (Cm-3)
X(H)
1.261X10-5
1.210X10-5
1.198 X10-5
1.223 X10-5
3.154 X10-6
3.026 X10-6
2.995 X10-6
3.058 X10-6
Ʈ(GP)
0.728
0.684
0.673
0.695
Table 15: The features measured of absorption line of Quasar SDSS J005006.35-005319.2
Line
Z
V (Km/Sec)
D(Mpc)
M
T(Gyr)
Z
Relative
n(H) (Cm-3)
X(H)
Ʈ(GP)
Lyα
4.303
1290960
25819.2
4.1854
1.1243
0.267
2.386X10-5
5.96X10-6
1.894
C IV
4.258
1277670
25553.4
4.1398
1.1385
0.270
2.327 X10-5
5.81 X10-6
1.824
He II
4.229
1268910
25378.2
4.1098
1.148
0.272
2.288 X10-5
5.72 X10-6
1.779
0.269
-5
-6
1.832
Average
Line
He I
Lyα
S
IV+OIV
Average
4.263
1279180
25583.6
4.145
1.1369
2.333 X10
5.83 X10
Table16: The features measured of absorption line of Quasar SDSS J000552.33-000655.6
Z
Z
V(Km/Sec)
D(Mpc)
M
T(Gyr)
n(H) (Cm-3)
X(H)
Relative
1821482.58 36429.6
6.071
5.988
0.730
0.180
5.658 X10-5
1.414 X10-5
3
5
1854227.23 37084.5
6.180
6.099
0.713
0.177
5.924 X10-5
1.481 X10-5
3
4
1758903.26 35178.0
5.863
5.777
0.763
0.187
5.172 X10-5
1.293 X10-5
5
7
1811537.69 36230.7
6.038
5.955
0.735
0.182
5.584 X10-5
1.396 X10-5
3
5
Volume 3, Issue 5, May 2014
Ʈ(GP)
6.916
7.409
6.044
6.790
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Table 17: The features measured of absorption line of Quasar SDSS J222851.23+011432.3
Z
Z
V(Km/Sec)
D(Mpc)
M
T(Gyr)
n(H) (cm-3)
X(H)
Relative
-5
6.477
1943333.39
38866.67 6.400
0.671
0.168
6.69 X10
1.672 X10-5
-5
6.570
1971168.72
39423.37 6.494
0.659
0.165
6.942 X10
1.735 X10-5
-5
6.385
1915758.388 38315.17 6.307
0.684
0.171
6.446 X10
1.611 X10-5
6.478
1943420.166
38868.4 6.400
0.671
0.168
6.693 X10-5
1.673 X10-5
Line
He I
NI
Lyα
Average
Ʈ(GP)
8.892
9.399
8.410
8.900
Fig9: Relationship between Optical depth and Redshift
Fig .10: Relationship between Velocity and Distance
.
Fig.11: Relation between Look back time and Redshift
4. SPECTRAL ANALYSIS of DOUBLE QUASARS
Four double quasars have been detected from SDSS and found Object ID (objID), Right ascension (Ra) and
Declination (Dec) as shown in table 18. Figures 12-15 show the absorption spectrum lines of these quasars. Tables 19-22
reflect the extrapolated chemical elements for these quasars. The features measured from absorption spectra are illustrated
in Tables 23-26. Also, we can find that the relationship between the optical depth as a function of different values of
redshift of some simple of double quasars, as shown in figure 16. Figure 17 illustrates the linear relationship between
recession velocities as a function of distance. By drawing the relationship between the Look back times as a function of the
redshift of different quasars, we find that whenever the redshift is less whenever the value of look back time is higher (see
figure 18).
Table 18: Object ID , Right ascension , and Declination for Selected Double Quasars
Quasar Name
objID
Ra
Dec
SDSS J115518.29+193942.2
1237668297664692248,
178.82622193
19.6617253
587742576439787545
SDSS J162026.14+120342.0
1237668366927004166,
245.10892899
12.06167583
587742645702099442,
SDSS J133907.13+131039.6
587738568175058991,
204.77974079
13.17767316
1237664289399963687,
SDSS J125418.94+223536.5
587742014361174098,
193.57895411
22.59348404
1237667735586078852,
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Fig. (12): Absorption Spectrum line of Quasar SDSS J115518.29+193942.2
Fig13: Absorption Spectrum line of Quasar SDSS J162026.14+120342.0
Fig.14: Absorption Spectrum line of Quasar SDSS J133907.13+131039.6
Fig.15: Absorption Spectrum line of Quasar SDSS J125418.94+223536.5
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Table (19): The chemical composition of Quasar SDSS J115518.29+193942.2
F(λ)
Chemical Element
obs
Rest
Å
Å
C III
147.67
3852.033
1909
C II
76.17
4669.705
2326
Mg II
87.05
5606.311
2800
Ne IV
72.35
4900.14
2439.5
Ne V
48.52
6847.68
3346.79
Table (20): The chemical composition of Quasar SDSSJ162026.14+120342.0
Chemical Element
F(λ)
obs
Rest
Å
Å
C III
18.54
4104.76
1909
Mg II
13.15
5985.41
2795.5
Ne IV
9.101
5227.2
2439.5
C II
9.425
4989
2326
He I
5.9816
8245.161
4388
Table (21): The chemical composition of Quasar SDSSJ133907.13+131039.6
Chemical Element
F(λ)
obs
Rest
Å
Å
Lyα
59.57
3932.99
1215.42
NV
41.43
4005.232
1239.42
OI
28.23
4219.036
1305.53
C II
26.5
4293.13
1335.32
C IV
29.58
4968.9
1545.86
Table (22): The chemical composition of Quasar SDSSJ125418.94+223536.5
Line
Z
C III
C II
Mg II
Ne IV
Ne V
Average
1.017
1.007
1.002
1.008
1.046
1.016
Line
Z
C III
Mg II
1.150
1.141
Chemical Element
F(λ)
Lyα
NV
C IV
C III
O IV
28.0571
obs
Å
5613.03
Rest
Å
1215.24
10.65
8.95
5.8913
5.8913
5720.76
7110.45
8715.24
4760.76
1239.42
1545.86
1909
1033.3
Table (23): The features measured of Quasar SDSS J115518.29+193942.2
Z
V(Km/Sec)
D(Mpc)
M
T(Gyr)
Relative
n(H) (cm-3)
305348.297
302283.534
300676.178
302599.713
313813.236
304944.191
6106.965
6045.670
6013.523
6051.994
6276.264
6098.883
0.189
0.123
0.064
0.131
0.306
0.162
4.790
4.826
4.846
4.822
4.691
4.795
9.647
15.252
29.167
14.229
5.669
14.793
1.314X10-6
1.294 X10-6
1.284 X10-6
1.296 X10-6
1.370 X10-6
1.311 X10-6
X(H)
Ʈ(GP)
3.286 X10-7
3.236 X10-7
3.210 X10-7
3.241 X10-7
3.426 X10-7
3.279 X10-7
0.024
0.023
0.023
0.023
0.026
0.024
Table (24): The features measured of Quasar SDSSJ162026.14+120342.0
Z
n(H) (CmV(Km/Sec)
D(Mpc)
M
T(Gyr)
X(H)
Relative
3)
345064.431
6901.288
0.568
4.354
2.783
1.590X10-6 3.976X10-7
342326.238
6846.524
0.549
4.382
2.895
1.570X10-6 3.926X10-7
Volume 3, Issue 5, May 2014
Ʈ(GP)
0.0325
0.0319
Page 58
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Volume 3, Issue 5, May 2014
Ne IV
1.142
342820.250
6856.405
0.553
4.377
2.883
1.574X10-6
C II
1.144
343465.176
6869.303
0.557
4.370
2.847
1.578X10-6
ISSN 2319 - 4847
3.935X10-7
3.947 X107
0.0320
0.0322
-
He I
0.879
263707.452
5274.149
0.476
5.330
1.852
1.061X10-6
2.653 X10
7
0.0177
Avera
ge
1.091
327476.709
6549.534
0.541
4.563
2.652
1.475X10-6
3.687X10-7
0.0293
Line
Z
Lyα
NV
OI
C II
C IV
Average
2.235
2.231
2.231
2.215
2.214
2.225
Table (25): The features measured of Quasar SDSS J133907.13+131039.6
Z
n(H) (CmV(Km/Sec)
D(Mpc)
M
T(Gyr)
X(H)
Relative
3)
670773.0
13415.46
1.999
2.358
0.618
5.421X10-6 1.355X10-6
669461.1
13389.22
1.994
2.363
0.62
5.399X10-6 1.349X10-6
669499.5
13389.99
1.995
2.363
0.619
5.400X10-6 1.350X10-6
664517.0
13290.34
1.975
2.381
0.627
5.317X10-6 1.329X10-6
664298.1
13285.96
1.975
2.382
0.626
5.313X10-6 1.328X10-6
667709.8
13354.2
1.988
2.369
0.622
5.370X10-6 1.342X10-6
Ʈ(GP)
0.205
0.203
0.203
0.199
0.199
0.202
Table (26): The features measured of Quasar SDSS J125418.94+223536.5
Line
Z
Lyα
3.618
V(Km/Sec)
1085659.6
D(Mpc)
M
21713.19
3.477
T(Gyr)
Z
Relative
n(H) (Cm-3)
1.383
0.328
1.576X10-5
Ʈ(GP)
X(H)
3.941 X10-6
1.017
-5
-6
NV
C IV
C III
3.615
3.599
3.565
1084702.5
1079901.8
1069602.9
21694.05
21598.04
21392.06
3.4745
3.457
3.422
1.384
1.391
1.407
0.365
0.330
0.334
1.573 X10
1.557 X10-5
1.522 X10-5
3.933 X10
3.892 X10-6
3.806 X10-6
1.014
0.998
0.965
O IV
Average
3.607
3.601
1082200.7
1080413.5
21644.01
21608.27
3.465
3.459
1.388
1.391
0.330
0.337
1.564 X10-5
1.558 X10-5
3.912 X10-6
3.897 X10-6
1.005
1.000
Fig.16: Relation between Optical depth and Redshift
Fig.17: Relation between Velocity and Distance
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Volume 3, Issue 5, May 2014
ISSN 2319 - 4847
Fig18: Relation between Lookback time and Redshift
5. CONCLUSIONS
In this paper, the absorption spectra of eight single and four double quasars were studied and analyzed, We found that
mostly elements of spectra single quasars are (O II, O III, Mg, H Ɣ, Ne II, C III, He II, and sometime He I, N I), but mostly
elements of spectra double quasars are (C II, C III, Mg II, Ne IV, N V, and Sometimes O I, O IV, Ne V). From the results,
it is found that the single quasars span a redshift range of 0.335 ≤ z ≤ 6.47and the double quasars span a redshift of 1.01 ≤
z ≤ 3.64. The features of absorption line, speed, distance, relativistic redshift, magnification, post-recombination density,
look back time and Gunn-Peterson Optical depth were calculated. The value of magnification always less than one if speed
of quasar is less than the speed of light (if v<c always M<1). .Also the results indicated that whenever the redshift is less
whenever the value of look back time is higher and the value of optical depth is less.
References
[1] Allison. R. Hill, S. C. Gallagher, R. P. Deo, E. Peeters and Gordon. T. Richards," Characterizing Quasars in the Midinfrared: High Signal-to-Noise Spectral Templates", Mon. Not. R. Astron. Soc., 2013.
[2] Valentina D., " Quaser Absorption Spectra: Probes Of The Baryonic Gas At High Redshift ", Ph.D. thesis submitted to
Isis-international school for advanced studies,1999.
[3] Gisella D. "A comprehensive analysis of optical and near-infrared spectroscopy of z_6 quasars",Ph.D thesis submitted
to Combined Faculties of the Natural Sciences and Mathematics ,University of Heidelberg, Germany,2011.
[4] Huang, W.-R., Chen, Z.-F., Qin ,Y.-P., . Li , Liao M.-S, He, R.-H., Han W.-W., F., Zhong, Y.-Q., Gan J.-Q. and Zhou
,W. "Identification of MgII Absorption Line Systems from SDSS Quasar Catalogue" J. Astrophys. Astr., 32, 277–280,
2011.
[5] Liddle, A. , "An Introduction to Modern Cosmology – second Edition ", West Sussex PO19 8SQ, 2003.
[6] "Quasar Absorption Lines" http://astro.berkeley.edu/~ay216/08/NOTES/Lecture26-08.pdf,1996.
[7] Sloan Digital Sky Survey http://www.sdss.org
Authors
Bushra Q. Al-Abudi received Ph.D. degree in Astronomy in 2002 from University of Baghdad, College of
Science, Department of Astronomy and Space . Currently she is professor in Astronomy department and her
research interests include spectroscopy and photometry analysis of binary stars.
Nuha S. Fouad received B.Sc. degrees in Astronomy in 2012 from university of Baghdad, College of Science,
Department of Astronomy and Space. Currently she is M.Sc. student in Astronomy department.
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