J/AJ/155/81 Diffuse X-ray-emitting gas in major mergers (Smith+, 2018)
Diffuse X-ray-emitting gas in major mergers.
Smith B.J., Campbell K., Struck C., Soria R., Swartz D., Magno M., Dunn B.,
Giroux M.L.
<Astron. J., 155, 81-81 (2018)>
=2018AJ....155...81S 2018AJ....155...81S (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies ; Interstellar medium ; Star Forming Region ;
X-ray sources ; Ultraviolet ; Infrared
Keywords: galaxies: evolution - galaxies: ISM - galaxies: star formation -
galaxies: interactions - X-rays: ISM
Abstract:
Using archived data from the Chandra X-ray telescope, we have extracted
the diffuse X-ray emission from 49 equal-mass interacting/merging
galaxy pairs in a merger sequence, from widely separated pairs to
merger remnants. After the removal of contributions from unresolved
point sources, we compared the diffuse thermal X-ray luminosity from
hot gas (LX(gas)) with the global star formation rate (SFR). After
correction for absorption within the target galaxy, we do not see a
strong trend of LX(gas)/SFR with the SFR or merger stage for galaxies
with SFR>1 M☉/yr. For these galaxies, the median LX(gas)/SFR
is 5.5x1039 ((erg/s)/M☉/yr), similar to that of normal spiral
galaxies. These results suggest that stellar feedback in star-forming
galaxies reaches an approximately steady-state condition, in which a
relatively constant fraction of about 2% of the total energy output
from supernovae and stellar winds is converted into X-ray flux. Three
late-stage merger remnants with low SFRs and high K-band luminosities
(LK) have enhanced LX(gas)/SFR; their UV/IR/optical colors suggest
that they are post-starburst galaxies, perhaps in the process of
becoming ellipticals. Systems with LK<1010 L☉ have lower
LX(gas)/SFR ratios than the other galaxies in our sample, perhaps
due to lower gravitational fields or lower metallicities. We see no
relation between LX(gas)/SFR and Seyfert activity in this sample,
suggesting that feedback from active galactic nuclei is not a major
contributor to the hot gas in our sample galaxies.
Description:
In the current study, we aim to better understand the spiral-to-elliptical
transformation process and the origin of the hot gas in ellipticals by
using archival X-ray imaging data from the Chandra telescope to measure
the hot ionized interstellar gas in a sample of 49 major mergers. We
will compare these to models of hot gas production during mergers.
All of the Chandra data used in this study came from the Advanced CCD
Imaging Spectrometer (ACIS) S-array. We only used data from the S3 chip
on this array since it has the highest sensitivity. The basic data
reduction was done using the Chandra Interactive Analysis of Observations
(CIAO) software version 4.7. All of our targets are small enough on the sky
that they fit within the 8.3'x8.3' field of view of the ACIS-S3 chip, and
nearby contemporaneous background can be defined on the same CCD. The data
were deflared, and the good time intervals (GTIs) were identified. The
GTIs were extracted by using the CIAO command deflare with the sigma
clipping routine with nsigma=3 and a bin size of 259.28 s, restricting
the energy range to 0.3-8 keV. The final Chandra exposure times range
from 2.6 ks to 456 ks, with a median time of 31.5 ks.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 81 49 Basic Data on Sample Galaxies
table2.dat 77 49 X-Ray Data
table3.dat 82 49 X-Ray Parameters and Results for Galactic
Absorption Correction Only
table4.dat 82 49 X-Ray Luminosities Including Internal Absorption
Correction from UV/IR
table5.dat 119 18 X-Ray Fits for More Complex Models
table6.dat 58 49 Ratios Involving the Diffuse MEKAL Component
of the X-Ray Luminosity
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See also:
IX/45 : The Chandra Source Catalog, Release 1.1 (Evans+ 2012)
J/AJ/126/1183 : Major galaxy mergers at z≲3 (Conselice+, 2003)
J/AJ/133/791 : Spitzer photometry of normal & interacting galaxies
(Smith+, 2007)
J/AJ/139/1212 : SDSS photometry of interacting galaxies (Smith+, 2010)
J/ApJ/713/330 : Spitzer observations of major-merger galaxies (Xu+, 2010)
J/AJ/148/137 : Merging galaxies in COSMOS to z∼1 (Lackner+, 2014)
J/ApJS/218/6 : The Spitzer Interacting Galaxies Survey (SIGS)
(Brassington+, 2015)
J/ApJ/829/78 : Dust properties of major-merger galaxy pairs
(Domingue+, 2016)
J/ApJS/222/16 : Heschel obs. of major-merger pairs of z<0.1 galaxies
(Cao+, 2016)
J/MNRAS/464/3882 : Mergers and galaxy-galaxy interactions (Weston+, 2017)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 16 A16 --- Name Galaxy name(s)
18 I1 --- Stage [1/7] Merger stage (1)
20- 24 F5.1 Mpc Dist [9.8/184] Distance
26- 30 F5.2 10+35W LFUV [0.27/93.68]? GALEX/FUV band luminosity
(in 1042 erg/s)
32- 37 F6.2 10+35W LNUV [0.88/109.18]? GALEX/NUV band luminosity
(in 1042 erg/s)
39- 45 F7.2 10+35W L24 [0.17/2929.16] Spitzer 24 µm band
luminosity (in 1042 erg/s)
47- 51 F5.2 [Lsun] log(LFIR) [8.4/12.19] Log of the total FIR luminosity
(LFIR) (2)
53- 57 F5.2 [Lsun] log(LK) [9.06/12.36] Log of the 2MASS Ks band
luminosity (LK) (3)
59- 63 F5.2 [-] log(LFIR/LK) [-3.16/0.79] FIR to K-band luminosity ratio
65- 70 F6.2 Msun/yr SFR [0.03/450.05] Star formation rate
72- 81 A10 --- AGN Galaxy listed as an AGN in NED?
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Note (1): We did a rough classification of the 49 systems in our sample into
seven merger stages based on morphology. Stages are defined as follows:
1 = Separated but interacting pair with small tails or no tails;
2 = Separated pair with moderate to long tails;
3 = Pair with disks in contact;
4 = Common envelope, two nuclei, and tails;
5 = Single nucleus and two strong tails;
6 = Single nucleus but weak tails;
7 = Disturbed elliptical with little or no tails.
Note (2): LFIR from 42.5-122.5 µm (Helou et al. 1985ApJ...298L...7H 1985ApJ...298L...7H) for
these systems, calculated from IRAS 60 µm and 100 µm flux densities.
Note (3): Calculated using the equation given in Brassington et al.
(2007MNRAS.377.1439B 2007MNRAS.377.1439B; from Seigar 2005MNRAS.361L..20S 2005MNRAS.361L..20S):
log(LK)=11.364-0.4 KT+log(1+z)+2log(D), where KT is the total K
magnitude, z is the redshift, LK is the K-band luminosity in solar
luminosities, and D is the distance (in Mpc).
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Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 16 A16 --- Name Galaxy name(s)
18- 22 F5.1 ksec ExpTime [2.6/455.8] The final Chandra exposure time
24- 28 I5 --- Set1 [809/15077] Data set 1
30- 34 I5 --- Set2 [315/15619]? Data set 2
36- 40 I5 --- Set3 [3041/14914]? Data set 3
42- 46 I5 --- Set4 [3042/14915]? Data set 4
48- 52 I5 --- Set5 [3043/13948]? Data set 5
54- 58 I5 --- Set6 [3044/15869]? Data set 6
60- 63 F4.2 10+32W PSL [0.01/3.28] Point source limit (in 1039 erg/s)
65- 70 F6.2 10+32W LX(HMXB) [0.02/333] X-ray luminosity (0.3-8.0 keV) for
unresolved high-mass X-ray binaries (HMXBs)
(in 1039 erg/s)
72- 77 F6.2 10+32W LX(LMXB) [0.07/139.28] X-ray luminosity (0.3-8.0 keV) for
unresolved low-mass X-ray binaries (LMXBs)
(in 1039 erg/s)
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Byte-by-byte Description of file: table3.dat table4.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 16 A16 --- Name Galaxy name(s)
18 A1 --- l_F(0.3-8) [<] Limit flag on F(0.3-8) (not in Table 4)
19- 24 F6.2 10-17W/m2 F(0.3-8) [0.11/133.28]? Total observed X-ray
(0.3-8 keV) flux (in 10-14 erg/s/cm2)
(not in Table 4)
26- 29 F4.2 10-17W/m2 e_F(0.3-8) [0.05/2.9]? Lower limit uncertainty in
F(0.3-8) (not in Table 4)
31- 34 F4.2 10-17W/m2 E_F(0.3-8) [0.15/3.32]? Upper limit uncertainty in
F(0.3-8) (not in Table 4)
36- 39 F4.1 10+20/cm2 NH [0.5/72.1]? Galactic hydrogen column
density
41- 44 F4.1 --- chi2r [0.7/13.5]? Best-fit reduced chi-squared
χ2ν
46- 51 F6.1 --- Chi2 [3.2/5751.7]? Chi-squared Χ2
53- 55 I3 --- DOF [4/524]? Degrees of Freedom
57 A1 --- l_LX(M) [<] Limit flag on LX(M)
58- 63 F6.1 10+32W LX(M) [0.5/4249.6]? MEKAL X-ray (0.3-8 keV)
luminosity (in 1039 erg/s) (1)
65- 69 F5.1 10+32W e_LX(M) [0.1/170.7]? Uncertainty in LX(M)
(in 1039 erg/s)
71 A1 --- l_LX(PL) [<] Limit flag on LX(PL)
72- 77 F6.1 10+32W LX(PL) [0.1/1488.4]? Power law X-ray (0.3-8 keV)
luminosity (in 1039 erg/s) (1)
79- 82 F4.1 10+32W e_LX(PL) [0.4/35.6]? Uncertainty in LX(PL)
(in 1039 erg/s)
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Note (1): Calculated assuming kT (gas temperature) is fixed at 0.3 keV.
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 A11 --- Name Galaxy name
13- 17 A5 --- Model Final best model (1)
19- 21 F3.1 --- chi2r [0.8/1.7] Best-fit reduced chi-squared
χ2ν
23- 27 F5.1 --- Chi2 [18.7/842.1] Chi-squared Χ2
29- 31 I3 --- DOF [11/518] Degrees of Freedom
33- 36 F4.1 10+20/cm2 NH(M) [0.6/61.6] MEKAL Galactic hydrogen column
density
38- 41 F4.1 10+20/cm2 e_NH(M) [0.7/11.5]? Uncertainty in NH(M)
43 A1 --- n_NH(M) [F] Note on NH(M) (F=Fixed column density)
45- 50 F6.1 10+20/cm2 NH(PL) [1.3/1268.9]? Power law Galactic hydrogen
column density
52- 56 F5.1 10+20/cm2 e_NH(PL) [1.7/330.2]? Uncertainty in NH(PL)
58- 61 A4 --- n_NH(PL) [F tied] Note on NH(PL) (F=Fixed column
density; tied=MEKAL and power-law absorbing
columns tied together)
63- 66 F4.2 keV kT1 [0.2/0.69] First gas temperature
68- 71 F4.2 keV e_kT1 [0.01/0.12]? Uncertainty in kT1
73 A1 --- n_kT1 [F] Note on kT1 (F=Fixed temperature)
75- 78 F4.2 keV kT2 [0.58/1.85]? Second gas temperature
80- 83 F4.2 keV e_kT2 [0/0.28]? Uncertainty in kT2
85- 89 F5.1 10+32W LX(M)1 [5.6/815] First absorption-corrected MEKAL
X-ray (0.3-8 keV) luminosity
(in 1039 erg/s)
91- 95 F5.1 10+32W e_LX(M)1 [1.1/184.6] Uncertainty in LX(M)1
(in 1039 erg/s)
97-101 F5.1 10+32W LX(M)2 [20.5/387.2]? Second absorption-corrected
MEKAL X-ray (0.3-8 keV) luminosity
(in 1039 erg/s)
103-107 F5.1 10+32W e_LX(M)2 [2.5/106.5]? Uncertainty in LX(M)2
(in 1039 erg/s)
109-113 F5.1 10+32W LX(PL) [14.9/852] Absorption-corrected power law
X-ray (0.3-8 keV) luminosity
(in 1039 erg/s)
115-119 F5.1 10+32W e_LX(PL) [1/217.6] Uncertainty in LX(PL)
(in 1039 erg/s)
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Note (1): Models are defined as follows:
1T = One temperature component, absorbing column fixed;
2T = Two temperature components, with absorbing column fixed;
1T1N = One temperature component, one absorbing column (absorbing columns for
MEKAL and power-law components tied together);
2N = Fitting for MEKAL and power-law absorbing columns separately, with
fixed single-component MEKAL temperature;
1T2N = One temperature component; MEKAL and power-law absorption fit
separately;
2T1N = Two MEKAL temperature components; MEKAL and power-law absorbing
columns tied together;
1TV2N = One temperature component, VMEKAL, two absorbing columns;
2TV = Two temperature components, VMEKAL, absorbing column fixed;
2TV1N = Two temperature components, VMEKAL, absorbing columns for MEKAL and
power-law components tied together. For the VMEKAL models, the
α/Fe ratios are Arp 217: 1.97±0.83; Arp 244: 1.96±0.56;
Arp 295: 6.56±14.86; Arp 299: 3.25±2.48; NGC 3256: 3±2.05;
NGC 6240: 3.61±0.97; Mrk 231: 2.86±0.58.
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 16 A16 --- Name Galaxy name(s)
18 A1 --- l_log(LX/LFIR)G [<] Limit flag on log(LX/LFIR)G
19- 23 F5.2 [-] log(LX/LFIR)G [-5.56/-1.27] X-ray (gas) to FIR
luminosity ratio for Galactic
absorption
25 A1 --- l_log(LX/LK)G [<] Limit flag on log(LX/LK)G
26- 30 F5.2 [-] log(LX/LK)G [-5.5/-3.69] X-ray (gas) to
K-band luminosity ratio for
Galactic absorption
32 A1 --- l_log(LX/SFR)G [<] Limit flag on log(LX/SFR)G
33- 37 F5.2 [10-7W/Msun/yr] log(LX/SFR)G [38.02/41.33] X-ray (gas)
luminosity to SFR ratio for
Galactic absorption
(in erg/s/M☉/yr)
39 A1 --- l_log(LX/LFIR)i [<] Limit flag on log(LX/LFIR)i
40- 44 F5.2 [-] log(LX/LFIR)i [-4.51/-1.23]? X-ray (gas) to
FIR luminosity ratio for
internal absorption
46 A1 --- l_log(LX/LK)i [<] Limit flag on log(LX/LFIR)i
47- 51 F5.2 [-] log(LX/LK)i [-4.97/-2.87]? X-ray (gas) to
K-band luminosity ratio for
internal absorption
53 A1 --- l_log(LX/SFR)i [<] Limit flag on log(LX/LK)i
54- 58 F5.2 [10-7W/Msun/yr] log(LX/SFR)i [38.73/41.37]? X-ray (gas)
luminosity to SFR ratio for
internal absorption
(in erg/s/M☉/yr)
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History:
From electronic version of the journal
References:
Smith et al. Paper II. 2019AJ....158..169S 2019AJ....158..169S
(End) Tiphaine Pouvreau [CDS] 18-Oct-2018