J/AJ/159/17 Physical properties of SFRs in NGC 3395/NGC 3396 (Weistrop+, 2020)
Physical properties of the star-forming regions in the interacting galaxies
NGC 3395/NGC 3396.
Weistrop D., Nelson C.H., Angione R., Bachilla R.
<Astron. J., 159, 17 (2020)>
=2020AJ....159...17W 2020AJ....159...17W (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, spectra ; Star Forming Region ; Redshifts ; Abundances ;
Photometry, UBVRI
Keywords: Interacting galaxies - Wolf-Rayet stars
Abstract:
We report long-slit spectroscopy of the early major merger galaxies
NGC 3395/NGC 3396. The spectra are consistent with those for star-forming
galaxies, but there is some indication of LINER-like active galactic
nucleus activity in the center of NGC 3396. The total star formation rate
in the regions observed is 2.83 M☉/yr, consistent with estimates
for the entire galaxies. The highest abundances are in the centers of
the galaxies, with the abundances decreasing with distance. There is a
correlation between high abundance and high ionization parameter, both
of which can be attributed to the presence of massive stars. Modeling with
SB 99 indicates the star-forming regions are younger than 10 Myr. There
are 1000-2000 WNL stars in the system, along with several thousand O stars,
consistent with the ages of the star-forming regions. The highest electron
densities are found in young regions with high star formation rates.
The electron temperatures are higher than results for non-interacting
galaxies, which is probably due to shock waves produced by the
galaxy-galaxy interaction, the outflow of gas from massive stars, and/or
collisions between gas clouds in the galaxies. There is star formation in
the bridge of material between the galaxies. These regions are among the
youngest in the system and have low abundances, suggesting the gas was
pulled from the outer parts of the galaxies. X-ray point sources, probably
high-mass X-ray binaries, are associated with several star-forming regions.
Description:
The star-forming regions in NGC 3395 and NGC 3396 were identified from
UBVR images obtained at the 1 m telescope at Mount Laguna Observatory
on 1997 May 8 UT using the 2048x2048 CCD camera. The instrument
configuration, seeing, reductions, and calibration of the images have
been previously described (Weistrop et al. 2012, J/AJ/143/98).
Spectra were obtained with the 2.1 m telescope at NOAO's Kitt Peak
Observatory on 1998 March 21-24 UT. The instrument configuration is
described in Weistrop et al. (2012, J/AJ/143/98). Long-slit spectra at
seven position angles (PA), selected to obtain spectra for as many blue
regions as possible, were acquired. The individual integrations were
1000 s with the following exceptions: one 300 s integration for
PA 136°, one 300 s integration for PA 12°; all integrations for
PA 83° were 1500 s. The spectra were calibrated and reduced as
described in Weistrop et al. (2012, J/AJ/143/98).
Objects:
-------------------------------------------------
RA (ICRS) DE Designation(s)
-------------------------------------------------
10 49 50.12 +32 58 58.2 NGC 3395 = UGC 5931
10 49 55.94 +32 59 26.4 NGC 3396 = UGC 5935
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File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 43 41 Region photometry
table4.dat 103 234 Redshift, reddening, and relative fluxes
for individual spectra
table5.dat 91 175 Results for individual spectra
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See also:
J/AJ/125/1696 : Star-forming knots in NGC 3395/3396 (Hancock+, 2003)
J/AJ/143/98 : Spectroscopy of star-forming regions in NGC 4194
(Weistrop+, 2012)
J/ApJS/208/10 : Effects of a κ-distribution in HII regions
(Dopita+, 2013)
J/MNRAS/432/998 : Kinematics of Arp 270 (NGC 3395) (Zaragoza-Cardiel+, 2013)
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 A2 --- Region Region identifier (see Figure 1 of this paper)
4- 12 F9.5 deg RAdeg Right Ascension in decimal degrees (J2000)
14- 21 F8.5 deg DEdeg Declination in decimal degrees (J2000)
23- 27 F5.2 mag Vmag [16.59/22.07]? V band magnitude
29- 33 F5.2 mag U-B [-1.16/0.07]? U-B colox index
35- 38 F4.2 mag B-V [0.18/0.52]? B-V colox index
40- 43 F4.2 mag V-R [0.23/0.5]? V-R colox index
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Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 deg PA [12/136] Position angle of slit, north
to east
5- 9 F5.1 arcsec Dist [-53.7/102.3] Distance of spectrum from slit
center
11- 17 F7.5 --- z [0.00511/0.00615] Spectroscopic redshift
19- 22 F4.2 mag E(B-V) [0/0.58]? The (B-V) color excess
24- 27 F4.2 --- O2-3727 [1.6/8.09]? Relative flux of [O II] 3727Å
(1)
29- 32 F4.2 --- O3-4363 [0.02/0.35]? Relative flux of [O III]
4363Å (1)
33 A1 --- u_O3-4363 [:] Uncertainty flag in O3-4363
35- 38 F4.2 --- Fe3-4658 [0.01/0.1]? Relative flux of [Fe III]
4658Å (1)
39 A1 --- u_Fe3-4658 [:] Uncertainty flag in Fe3-4658
41- 44 F4.2 --- He2-4686 [0.03/0.06]? Relative flux of [He II]
4686Å (1)
45 A1 --- u_He2-4686 [:] Uncertainty flag in He2-4686
47- 50 F4.2 --- Hb [1]? Relative Hβ flux (1)
52- 55 F4.2 --- O3-4959 [0.24/1.11]? Relative flux of [O III]
4959Å (1)
56 A1 --- u_O3-4959 [:] Uncertainty flag in O3-4959
58- 61 F4.2 --- O3-5007 [0.73/2.95]? Relative flux of [O III]
5007Å (1)
62 A1 --- u_O3-5007 [:] Uncertainty flag in O3-5007
64- 67 F4.2 --- N2-6548 [0.07/0.35]? Relative flux of [N II]
6548Å (1)
68 A1 --- u_N2-6548 [:] Uncertainty flag in N2-6548
70- 73 F4.2 --- Ha [2.84/2.86]? Relative Hα flux (1)
75- 78 F4.2 --- N2-6583 [0.27/0.91]? Relative flux of [N II]
6583Å (1)
79 A1 --- u_N2-6583 [:] Uncertainty flag in N2-6583
81- 84 F4.2 --- S2-6716 [0.24/1.07]? Relative flux of [S II]
6716Å (1)
85 A1 --- u_S2-6716 [:] Uncertainty flag in S2-6716
87- 90 F4.2 --- S2-6731 [0.19/0.69]? Relative flux of [S II]
6731Å (1)
91 A1 --- u_S2-6731 [:] Uncertainty flag in S2-6731
93- 99 E7.1 cW/m2/nm FHb [9.3e-17/4.2e-14]? Measured Hβ flux
(in erg/s/cm2/Å)
100 A1 --- u_FHb [:] Uncertainty flag in FHb
102-103 I2 pix Slit [2/15] Combined spectrum slit height
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Note (1): Relative to Hβ. Reddening corrected.
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 deg PA [12/136] Position angle of slit, north
to east
5- 9 F5.1 arcsec Dist [-41.1/98.7] Distance of spectrum from
slit center
11- 14 F4.2 Msun/yr SFR [0/0.18] Star formation rate
16- 19 F4.2 Msun/yr e_SFR [0/0.02] Uncertainty in SFR
21- 24 F4.2 [-] 12+log(O/H) [8.55/8.98]? Oxygen abundance (1)
26- 29 F4.2 [-] E_12+log(O/H) [0.01/0.23]? Upper uncertainty
in 12+log(O/H)
31- 34 F4.2 [-] e_12+log(O/H) [0.01/0.31]? Lower uncertainty
in 12+log(O/H)
36- 39 F4.2 [-] log(q) [6.8/8.28]? Log of the ionization
parameter
41- 44 F4.2 [-] E_log(q) [0.02/0.46]? Upper uncertainty in log(q)
46- 49 F4.2 [-] e_log(q) [0.02/0.31]? Lower uncertainty in log(q)
51- 53 F3.1 Myr Age(M6) [1.6/5.5] Age calculated using Model 6
55- 58 F4.2 Myr e_Age(M6) [0/0.9] Uncertainty in Age(M6)
60- 63 F4.1 Myr Age(M2) [6/10] Age calculated using Model 2
65- 68 F4.2 Myr e_Age(M2) [0/0.65] Uncertainty in Age(M2)
70- 73 F4.1 10+1cm-3 n(e) [0.2/24]? Electron density
75 A1 --- l_n(e) [<] Limit flag on electron density range
76- 80 F5.2 10+3cm-3 b_n(e) [0.03/29]? Lower limit of n(e) range
82- 85 F4.2 10+3cm-3 B_n(e) [0.2/0.36]? Upper limit of n(e) range
87- 91 A5 --- Region Galaxy feature identified in Figure 3
(see table2.dat)
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Note (1): Calculated using Dopita et al. 2013, J/ApJS/208/10.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 19-Feb-2020