J/ApJ/734/65 CI radial velocities with HST/STIS (Jenkins+, 2011)
The distribution of thermal pressures in the diffuse, cold neutral medium of our
Galaxy.
II. An expanded survey of interstellar C I fine-structure excitations.
Jenkins E.B., Tripp T.M.
<Astrophys. J., 734, 65 (2011)>
=2011ApJ...734...65J 2011ApJ...734...65J
ADC_Keywords: Interstellar medium ; Spectra, ultraviolet ; Stars, nearby ;
Radial velocities
Keywords: ISM: atoms - ISM: kinematics and dynamics - ISM: lines and bands -
techniques: spectroscopic - turbulence - ultraviolet: ISM
Abstract:
We analyzed absorption features arising from interstellar neutral
carbon that appeared in the UV spectra of 89 stars recorded in the
highest resolution echelle modes of the Space Telescope Imaging
Spectrograph on board the Hubble Space Telescope so that we could
determine the relative populations of collisionally excited
fine-structure levels in the atom's electronic ground state. From this
information, in combination with molecular hydrogen rotation
temperatures, we derive the distribution of thermal pressures in the
diffuse, cold neutral medium (CNM). We find a lognormal pressure
distribution (weighted by mass) with a mean in log(p/k) equal to 3.58
and an rms dispersion of at least 0.175dex that plausibly arises from
turbulence with a characteristic Mach number in the range 1<M<4.
Description:
Our earlier survey (Jenkins & Tripp, 2001ApJS..137..297J 2001ApJS..137..297J) covered only
21 stars that were observed with the guaranteed observing time granted
to the HST/STIS instrument definition team. In order to maximize the
observing efficiency, the target stars in this study were located
within two Galactic longitude intervals, ones where the HST continuous
viewing zones intersected the Galactic plane (99<GLON<138°,
254<GLON<313°). We downloaded from Multimission Archive at the
Space Telescope Science Institute (MAST) virtually all of the
observations performed at wavelengths that covered two or more CI
transitions. Once again, we made use of the broad wavelength coverage
of STIS to examine as many multiplets as possible. These spectra had a
resolving power in radial velocity equal to 2.6km/s.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 136 89 Properties of the sight lines
table4.dat 80 2416 Observed and calculated quantities in specific
velocity channels
--------------------------------------------------------------------------------
See also:
B/hst : HST Archived Exposures Catalog (STScI, 2007)
J/ApJS/187/149 : StarCAT: STIS UV echelle spectra of stars (Ayres, 2010)
J/ApJ/711/1236 : Equivalent width of H2 from FUSE (Jensen+, 2010)
J/ApJ/724/1389 : Mapping the diffuse UV sky with GALEX (Murthy+, 2010)
J/ApJ/702/1472 : Column densities for HI, AlIII, SiIV, CIV, OVI (Savage+, 2009)
J/ApJ/700/1299 : Gas-phase element depletions in the ISM (Jenkins, 2009)
J/ApJS/176/59 : FUSE survey of OVI in the disk of the Milky Way (Bowen+, 2008)
J/MNRAS/358/563 : Diffuse Interstellar Bands in 49 stars (Megier+, 2005)
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 A11 --- Star Target star identification
13- 25 A13 --- OName Other identification
27- 33 F7.3 deg GLON Galactic longitude
35- 41 F7.3 deg GLAT Galactic latitude
43- 54 A12 --- SpT MK spectral type
56- 59 F4.2 mag E(B-V) B-V color excess (1)
61- 64 F4.2 kpc Dist Distance (1)
66- 68 I3 K H2T ? Molecular hydrogen rotational temperature
from J=0 to 1 (2)
70- 71 I2 --- r_H2T ? H2T reference (3)
73-136 A64 --- Obs Archive exposure root name(s)
--------------------------------------------------------------------------------
Note (1): B-V color excesses and distances to the stars were either taken from
listings of the same stars in Bowen et al. (2008, Cat. J/ApJS/176/59)
or Jenkins (2009, Cat. J/ApJ/700/1299), or else they were computed by
using the same procedures that they invoked.
Note (2): The molecular hydrogen rotational temperature from J=0 to 1 that was
adopted as an indicator for the kinetic temperature of the intervening gas.
Note (3): Reference as follows:
1 = Savage et al. 1977ApJ...216..291S 1977ApJ...216..291S;
2 = Rachford et al. 2002ApJ...577..221R 2002ApJ...577..221R;
3 = Andre et al. 2003ApJ...591.1000A 2003ApJ...591.1000A;
4 = Pan et al. 2005ApJ...633..986P 2005ApJ...633..986P;
5 = Lee et al. 2007ApJ...655..940L 2007ApJ...655..940L;
6 = Burgh et al. 2007ApJ...658..446B 2007ApJ...658..446B;
7 = Sheffer et al. 2008ApJ...687.1075S 2008ApJ...687.1075S;
8 = Rachford et al. 2009ApJS..180..125R 2009ApJS..180..125R;
9 = Burgh et al. 2010ApJ...708..334B 2010ApJ...708..334B;
10 = J. M. Shull 2009, in preparation, listed in Burgh et
al. 2010ApJ...708..334B 2010ApJ...708..334B;
11 = Jensen et al. 2010, Cat. J/ApJ/711/1236
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 A11 --- Star Target star name
13- 17 F5.1 km/s RVel Radial Velocity
19- 24 F6.3 --- f1 f1 quantity (1)
26- 30 F5.3 --- e_f1 The 1σ error in f1
32- 37 F6.3 --- f2 f2 quantity (1)
39- 43 F5.3 --- e_f2 The 1σ error in f2
45- 53 E9.2 cm-2 N(CIt) Column density of CI in all 3 levels
55- 63 E9.2 cm-2 N(CII) ? Inferred column density of CII
65- 69 F5.3 --- g(low) ? Fraction of CI at low pressure
71- 74 F4.2 [cm-3.K] log(p/k) ? log(p/k) of the low pressure fraction
76- 80 F5.2 [-] log(I/I0) ? Log starlight intensity relative to standard
specified by Mathis et al. 1983A&A...128..212M 1983A&A...128..212M
--------------------------------------------------------------------------------
Note (1): Jenkins & Tripp, 2001ApJS..137..297J 2001ApJS..137..297J, devised a way to construct
a system of linear equations that could be solved to reveal the
apparent column densities N(CI), N(CI*), and N(CI**) as a function
of velocity. Once this has been done, we can evaluate the quantities
f1=N(CI*)/N(CItotal) and f2=N(CI**)/N(CItotal); where N(CI) refers
to the column density of atomic carbon in its 3P0 ground
fine-structure state, while N(CI*) and N(CI**) refer to the column
densities of the excited 3P1 and 3P2 levels, respectively.
The quantity N(CItotal) equals the sum of the column densities in
all three levels. See section 3 for further explanations.
--------------------------------------------------------------------------------
History:
* 22-Nov-2012: From electronic version of the journal
* 21-Jan-2013: table2, renamed "HD36408" into "HD36408B" to be
consistent with table4 (and target name in HST log)
References:
Jenkins & Tripp. Paper I. 2001ApJS..137..297J 2001ApJS..137..297J
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 22-Nov-2012