NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2019-05-23 T18:01:08 PDT
Help | Comment | NED Home

Notes for object NGC 4631

25 note(s) found in NED.


1. 2009A&A...503..409H
Re:NGC 4631
In this edge-on interacting spiral, the polarized emission is found in a roughly
X-shaped morphology, and comes mainly from the extraplanar regions. The disk
itself seems to be largely depolarized. Polarized emission is detected in the
central region and in each of the four extraplanar galaxy quadrants. The north
side is brighter in polarization than the south side. The brightest polarized
intensity is from the northeast quadrant, which is the region where the dramatic
HI extension studied by Rand (1994) is located. The polarized structure runs
roughly parallel with the HI extension, but fills the region between the disk
and the HI filament. The polarized fraction in this galaxy is less than one
percent in the central regions and increases with height above the midplane. At
the largest z-heights, the polarized fraction reaches as high as 30-40% in some
places. The magnetic field lines run along the X-shaped polarized morphology. In
the northeast quadrant, they run almost parallel to the HI extension, but these
seem to be unrelated. The polarized structures reported here have been observed
previously by Hummel et al. (1991) and Golla & Hummel (1994). The best estimate
of the Galatic foreground RM in this direction comes from the unconfused double
source in the field with an RM of -4 +/- 3 rad m^-2^; consistent with several
other sources in the field. The double background source lying just south of NGC
4631 is likely to be strongly affected by the halo of that galaxy, the brighter
lobe of which displays an RM of - 38 +/- 2 rad m^-2^.

2. 2008MNRAS.385..553D
Re:NGC 4631
NGC 4631: This galaxy is seen edge-on and its inclination renders
impossible the extraction of the kinematical parameters. The interaction
with the nearby dwarf galaxy is thought to be responsible for the warp
seen on the south-east side of the H{alpha} velocity field. Our H{alpha}
results are consistent with those of Golla, Dettmar & Domgoergen (1996).
As for the H I data, the results obtained by Rand (1994) show that the
maximum rotation velocity is 140 km s^-1^ and that the H I disc can be
modelled as having two distinct velocity components. CO observations
have demonstrated that the sources of these distinct velocities are the
spiral arms within the gas disc (Sofue et al. 1990).

3. 2005MNRAS.357..361S
Re:NGC 4631
NGC 4631. The submillimetre emission from this large galaxy (i= 85^deg^) has
been mapped over almost 14 arcmin, which corresponds to a linear distance of 52
kpc at the assumed distance to NGC 4631. This is 92 per cent of the optical
radius out to the 25 mag isophote. Several features are seen in the
submillimetre maps, including three central peaks, a warp in the western side of
the disc, knots of bright emission along the disc and filamentary structure
emanating like smoke from chimneys away from the plane of the disc.
The three central peaks may be explained from a dusty torus surrounding the
centre of the galaxy, as seen in the edge-on galaxies NGC 4388 and 4402. The
~80-arcsec separation of the two outer peaks corresponds to a diameter
of 4.9 kpc at the assumed distance to NGC 4631. The eastern peak is brighter
than the western one; however, in this case both are brighter than the
central peak. The 850-{mu}m emission (and arguably the 450-{mu}m emission) is
seen to peak twice more ~90 arcsec either side of the central peak,
corresponding to a linear distance of 5.5 kpc. These peaks may be due to the
increased line of sight column densities through two main spiral arms.

4. 2005ApJS..157...59L
Re:NGC 4631
NGC 4631 is an edge-on Sd galaxy at a distance of 6.9 Mpc. ULX1 (IXO 68) is
located on the dust lanes.

5. 2004ApJS..151..193S
Re:NGC 4631
4.2.7. NGC 4631 NGC 4631 is often erroneously presented as an example of
a "normal" spiral galaxy with a X-ray emitting halo (e.g., see Wang et
al. 2001). However, its large-scale-height nonthermal radio halo, warm
IRAS 60 to 100 micron flux ratio, high H{alpha} luminosity, and optically
disturbed morphology show it to be a highly atypical spiral galaxy. It
is a good example of a galaxy experiencing a mild, disk-wide, starburst
event (Golla & Wielebinski 1994).
In the optical and UV, NGC 4631 is a large, distorted, edge-on disk
galaxy, with many H II regions, dust filaments, and young stellar
clusters spread throughout the disk (Rand, Kulkarni, & Hester 1992;
Smith et al. 2001). Four ~35 kpc long H I spurs (Rand 1994) point to
strong tidal interactions with a dwarf elliptical companion, NGC 4627
(2.5' to the NW, ~5 kpc projected separation), and the edge-on
spiral galaxy NGC 4656 (32.4' to the SE, projected separation ~71
kpc). This interaction is thought to be the cause for the enhanced star
formation within the disk of NGC 4631. Molecular gas, and the recent
star formation, is less centrally concentrated in NGC 4631 than in the
other starburst galaxies of this sample (Golla & Wielebinski 1994; Golla
et al. 1996b; Golla 1999; Rand 2000), and Golla & Wielebinski describe
the nuclear star formation as an optically obscured "mild central
starburst." NGC 4631 was one of the first spiral galaxies discovered to
have a nonthermal radio halo (Ekers & Sancisi 1977), which has been
traced out to ~4' (z_max_ ~ 9 kpc) above and below the plane of the
galaxy (Golla & Hummel 1994). The observed alignment of the halo
magnetic field strongly suggests a large-scale outflow from the central
5 kpc of the disk (Golla & Hummel 1994), and although kinematic evidence
for outflow exists (cf. Martin & Kern 2001) (Golla et al. 1996b; Rand
2000) it is less compelling than in the more powerful starbursts
discussed earlier. A faint V-shaped pair of ~1.5 kpc-long
H{alpha}filaments is seen directly above the optically obscured nucleus,
reminiscent of the outflow cones seen in NGC 253 and NGC 4945 (see also
the HST WFPC2 images in Wang et al. 2001) (Rand et al. 1992). The
extraplanar H{alpha} emission is somewhat less vertically extended than
the radio emission (z_max_ ~ 5 kpc; Martin & Kern 2001) and is less well
organized into distinct multi-kiloparsec filaments and arcs than it is
in the other starburst galaxies (Rand et al. 1992; Hoopes et
al. 1999). Vertically extended diffuse X-ray emission was first robustly
detected by ROSAT PSPC observations (e.g., Wang et al. 1995; Vogler &
Pietsch 1996; Read et al. 1997; Dahlem et al. 1998). Results from the
Chandra ACIS-S observation of NGC 4631 were published by Wang et
al. (2001).

6. 2004ApJS..151..193S
Re:NGC 4631
The lack of central concentration in the star formation is dramatically
illustrated by the weakness of both soft and hard X-ray emission from
the central 2 kpc (see Figs. 10a, 10b, 10d, and 10e), both diffuse and
pointlike, in comparison to the starburst galaxies previously
considered. There is diffuse emission in the central 2 kpc, but at low
surface brightness (e.g., Wang et al. 2001).
There is no evidence of AGN-like activity in NGC 4631. The aligned
triple radio source ~6" to the SW of the dynamical center of the galaxy,
identified by Golla (1999) as a low-luminosity AGN candidate, has no
X-ray counterpart in the Chandra observations.
The diffuse X-ray emission is brightest and has its greatest vertical
extent, above the central ~4 kpc of NGC 4631 (Figs. 10g and 10h). This
region corresponds to the CO ring or bar (Rand 2000), is also the
location of the brightest radio emission (Golla & Hummel 1994; Golla
1999), and is bounded on the east by the most prominent giant H II
region visible within NGC 4631, CM67 (Crillon & Monnet 1969). Diffuse
X-ray emission definitely extends at least 180" (6.5 kpc) to the north
and 130" (4.7 kpc) to the south of the disk, and it appears to extend
out to the edge of the S3 chip at z ~ +-8 kpc at lower surface
brightness. Given the low diffuse X-ray flux, and its lack of
concentration into specific filaments or arcs, the S/N of the diffuse
X-ray images is low. This hinders a meaningful feature-by-feature
comparison with the H{alpha} emission, beyond the general observation
that the diffuse X-ray emission is brightest above the regions of the
disk with the most prominent extraplanar H{alpha} emission.
Based on the older ROSAT PSPC observations of NGC 4631 it was already
known that in terms of overall spatial extent the nonthermal radio
emission (at either 1.4 or 4.86 GHz; see Golla & Hummel 1994; Dahlem,
Lisenfeld, & Golla 1995) resembles the soft X-ray emission, the radio
emission being somewhat more extended and/or brighter to the north of
the disk, and most vertically extended above the same region of the disk
(see the X-ray/radio overlays presented in Wang et al. 1995; Vogler &
Pietsch 1996). It is difficult to make a more detailed morphological
comparison than this using either the ROSAT data or the Chandra
observations, in part due to the spatial filtering inherent in radio
imaging. Vogler & Pietsch (1996) suggest, rather convincingly in our
opinion, that "the northeastern and southeastern radio spurs seem to be
avoided by the X-ray emission," although both the radio and X-ray
emission are faint in these regions. Nevertheless, when comparing the
brightness of the soft X-ray emission to that of the nonthermal radio
emission on a location by location basis it is as easy to find regions
of apparent spatial correlation as to find regions with X-ray/radio
anticorrelation (based on the images presented in Wang et al. 1995,
Vogler & Pietsch 1996, or when overlaying the 1.4 GHz emission from the
NVSS survey on the Chandra X-ray images), leading us to speculate that
the halo magnetic fields and cosmic rays may be somewhat decoupled from
the hot plasma. Perhaps the only robust conclusion that can be drawn is
that there are magnetic fields and cosmic rays in the halo of NGC 4631,
in addition to hot plasma.

7. 2002AJ....124..675C
Re:UGC 07865
Huge galaxy; the NVSS flux density may be too low.

8. 1999ApJ...522..669H
Re:NGC 4631
The H{alpha}+[N II] image of this galaxy is shown in Figure 4. An
overlay of H{alpha} and X-ray emission for this galaxy, based on our
data, can be found in Wang et al. (1995). There appear to be significant
flat-fielding uncertainties on the south side of the disk, near the
bottom edge of the image, so we restrict our analysis to the north
side. The image shows a disturbed disk, most likely due to an
interaction with its companion galaxies NGC 4627 and NGC 4656. The disk
appears to be actively forming stars, and the disk-halo interface is
also very active in this galaxy. Rand et al. (1992) pointed out two
bright vertical "worms" of emission east of the nucleus on the north
side of the disk. We note that these worms are connected to longer,
fainter filaments, and the western worm appears to curve back around
toward the disk. There is an even larger loop of emission that surrounds
the two worms (indicated by the arrows in Fig. 4). It begins just east
of the easternmost worm and extends 3.5 kpc into the halo. Unfortunately
there is a seam in the image where the loop might reconnect to the
disk. The surface brightness at the top of the loop is about
12 pc cm^-6^. The large loop is barely visible in the H{alpha} image
presented by Rand et al. (1992, their Fig. 5). What appears to be
another filament about 3 kpc east of the giant loop in our image is
actually another seam. There is significant extraplanar emission in the
form of discrete features such as the loops and worms, and a smoother
component can be traced up to about 2 kpc on the north side. Donahue,
Aldering, & Stocke (1995) detected a faint halo extending 16 kpc from
the plane of NGC 4631, with a maximum brightness of
0.69 pc cm^-6^ arcsec^-2^. We could not confirm the detection because of
the smaller field of view of our observations. This emission is
probably related to the high star formation and disturbed nature of this
galaxy resulting from the tidal interaction, as it is too bright to be
caused by the metagalactic ionizing radiation field.

9. 1999A&A...343...51A
Re:NGC 4631
3.2. NGC 4631
In contrast to the compact torus structure observed at the centre of
M82, SCUBA maps of NGC 4631 reveal several 'hot-spots' separated by one
or more kpc. The picture that emerges is a galaxy which is less
dominated by circum-nuclear star-formation and, indeed, previous
observations in the H{alpha} emission-line have shown that about 2/3 of
the disk is undergoing enhanced star-formation (Rand et al. 1992). The
most active region, associated with the outflow of X-ray gas
(Fabbiano & Trinchieri 1984) and the origin of extensive H{alpha}
filaments in the halo, is the inner 3' covered by our SCUBA map.
The submm exhibits numerous extensions away from the midplane; from this
we infer that dust extends to a z-height of >= 30" (1.2 kpc). Images of
NGC 4631 at 1.3mm exhibit similar extra-planar structures (Braine et al.
1995) but we cannot confirm the reality of the most southerly extension
in the Braine et al. map (travelling up to 2.1 kpc away from the disk).
The lowest contour in the Braine et al. map is barely 2{sigma} and,
therefore, their most southerly filament must be considered doubtful. By
contrast, the extraplanar structures evident in Fig. 1 are at least
5{sigma} and manifest themselves in each of the 'composite' jiggle maps
making up the final image (as well as being present at both 450 and
850 microns). Notably, the submm filaments in Fig. 1 are not always
positionally coincident with 'vertical' extinction features evident in
optical images of NGC 4631 (Fig. 1). This is not surprising given that
the latter arise chiefly from optically thick material on the near side
of the disk whereas submm emission, being optically thin, probes the
whole line-of-sight.

10. 1998ApJS..118..401D
Re:NGC 4631
A bright point source in the disk, ~2.5' to the west of the galaxy
nucleus, dominates the HRI image of NGC 4631. We label this
NGC 4631:DWH 1 in the 1.5 keV PSPC image (Fig. 19). A second, fainter
point source (NGC 4631:DWH 4) is also visible in the galaxy plane just
to the east of the nucleus. There is also low surface brightness
diffuse emission that is patchy but extends perpendicular to the disk
plane.

11. 1998ApJS..118..401D
Re:NGC 4631
Raw images
The 1.5 keV map is dominated by disk emission, including compact sources
like the strong source ~2.8' west of the center labeled NGC 4631:DWH 1.
Some extraplanar emission is visible, which is more pronounced in the
0.75 keV band (Fig. 20). Most diffuse emission is seen around the
central region of NGC 4631. The 0.25 keV map shows only a little
emission, primarily north of the galaxy disk.
Final images
Removing the high surface brightness emission also removes part of the
halo emission visible in the 0.75 keV band. There are basically no
residuals in the 1.5 and 0.75 keV maps. In the 0.25 keV band, faint
structure north of the galaxy disk is now clearly visible. This emission
is most probably associated with the spectroscopically identified
thermal gas at ~0.05 and ~0.17 keV (SECTION 3.4.2). Using a different
point source subtraction technique, Read et al. (1997) succeeded in
displaying more extended halo emission.

12. 1998ApJS..118..401D
Re:NGC 4631
Three separate regions are identified from the PSPC data. These are the
halo, the galaxy disk, and the point source NGC 4631:DWH 1 (about
2.5' west of the nucleus). The other point sources have too few
counts to constrain their spectral parameters, but these counts are
excluded from the halo and disk spectra (see SECTION 3.4.3).
The total (joint) spectrum contains all photons within the PSPC and
ASCA regions. This includes disk and halo emission and both point
sources.

13. 1998A&AS..128..153M
Re:GB2 1239+328
NGC4631; UGC7865. Low-luminosity star-burst galaxy. References to
WSRT, NRAO interferometer, and Effelsberg maps, as well as
physical parameters in Condon & Broderick (1988AJ.....87.1064C)

14. 1997AJ....114.2428S
Re:NGC 4631
NGC 4631: This is an almost edge-on amorphous Sc galaxy, rich in CO gas. The
rotation velocity increases in a rigid-body fashion, as slowly as
~100 km s^-1^ /1 kpc. This galaxy is one of the exceptions. which show
rigid-body rotation.

15. 1995ApJS...98..477H
Re:NGC 4631
The location of the nucleus in this edge-on Sc spiral cannot be
identified with certainty on the 2-D spectrum. The spectrum we adopt for
the nucleus (Fig. 73) was extracted from an emission peak approximately
near the center of the long slit. Spectra at other places along the slit
look qualitatively similar.

16. 1995A&A...302..691D
Re:NGC 4631
This galaxy has two characteristics which differ clearly from the other
observed galaxies: first, it has a very large extent of the radio
continuum emission perpendicular to the plane which has already been seen
by Klein et al. (1984) at {lambda}2.8 cm. The central part of the galaxy
is dominated by the bright central source complex consisting of at least
three individual sources (Duric et al. 1982).
Another difference is the orientation of the magnetic field in this
galaxy: in the center the field lines are perpendicular to the plane,
whereas in the outer parts they are more parallel. In the north eastern
part the field lines seem to follow the prominent low frequency radio
spur (Hummel et al. 1991b).
The polarized emission is strongest in the central region, but shows
also a very patchy distribution.

17. 1994CAG1..B...0000S
Re:NGC 4631
Pair [with NGC 4627]
Hubble Atlas, p. 25
Sc(on edge)
H-2161-H
Jan 29/30, 1941
Cr Hi Sp Sp
120 min
NGC 4631 forms a close pair with the dwarf
elliptical NGC 4627 (dE,N) at a separation of
2.7', and a wide pair with NGC 4656 (Im; panels
327, S6) with a separation of 31'. These galaxies
are in the nearby group called the CnV II Cloud
(de Vaucouleurs 1975; Sandage and Tammann
1975a), which has of about 750 km/s.
A study of the 21-cm HI content of the wide
NGC 4631/4656 pair (Weliachew, Sancisi, and
Guelin 1978) gave evidence that a tidal
encounter had occurred or is now occurring
(Combes 1978) between this apparent pair. At an
assumed redshift distance of 12 Mpc (H = 50) the
projected linear separation of NGC 4631 from
NGC 4656 is 108 kpc. If a smaller distance of
5 Mpc is used, based on the stellar content
(Sandage and Tammann 1974d), the projected
linear separation is 44 kpc. At this distance, the
projected linear separation of the much closer
NGC 4631/4627 pair is only 4 kpc.
NGC 4631 is highly resolved into brightest
stars starting at about B = 19. However, because
the galaxy is viewed nearly edge on, the dust
obscuration is high and variable, making
photometric studies of the stellar content difficult
and the results uncertain.

18. 1994CAG1..B...0000S
Re:NGC 4631
Pair [with NGC 4627]
Hubble Atlas, p. 25
Sc(on edge)
H-3634-S
Feb 18/19, 1963
103aO + GG13
25 min
The dwarf companion NGC 4627 has a
nucleus and is surrounded by a swarm of about
ten images brighter than B = 22. These may be
globular clusters similar to the case in NGC 205
(panel 25), the companion to M31. Also like
NGC 205, NGC 4627 has tidal tails pointing
toward and away from its larger companion. This
is clear evidence of a close encounter, pointed out
and shown well in the deep photograph in the
Atlas of Peculiar Galaxies (Arp 1966). A similar
case is the pair NGC 1531/1532 (panels 197,
337).
NGC 4627 has nearly the same redshift as
NGC 4631. Ulrich, quoted by Weliachew et al.
(1978), has measured v_o(4631) = 647 km/s.
Chincarini and Rood (1971) quote v_o(4627) =
727 km/s. Combes (1978), who has calculated
encounter parameters for the three-galaxy
interaction, suggests that NGC 4627 was once a
recent star-producing Im dwarf whose HI was
swept out, leaving a nucleated dwarf E galaxy
from the encounter.

19. 1986AnTok..212.127T
Re:KUG 1239+328B
Edge-on spiral with many a high UV-excess clumps of HII regions.

20. 1976RC2...C...0000d
Re:NGC 4631
= Arp 281
= Holm 442a
= Kara[72] 350a (NGC 4656 = Kara[72] 350b).
Interacting pair with NGC 4627 at 2.5 arcmin
Photograph:
Ap. J., 151, 117, 1968.
Ap. J., 194, 559, 1974.
Astr. Ap., 2, 1, 1969.
Vistas in Ast.,Vol. 14, 216, 1972.
Photometry (12 Color):
Ap. J., 145, 36, 1966.
Spectrum:
Sov. A.J., 13, 593, 1970.
Rotation Curve and Mass Determination:
Ap. J., 140, 1620, 1622, 1964.
Astr. Ap., 2, 1, 1969.
Vistas in Ast., Vol. 14, p.239, 1972.
HII Regions and Distance Modulus:
Ap. J., 194, 559, 1974.
Interferometry H{alpha}:
Astr. Ap., 2, 1, 1969.
HI 21cm:
Ap. J., 150, 8, 1967.
Ap. J., 151, 117, 1968.
Astr. Ap., 3, 402, 1969.
Radio Observations:
Ap. J., 150, 413, 1967.
M.N.R.A.S., 144, 143, 1969.
M.N.R.A.S., 159, 15P, 1972.
Astr. Ap., 29, 231, 1973.

21. 1973UGC...C...0000N
Re:UGC 07865
Arp 281
SB(s)d (de Vaucouleurs), Sc+ (Holmberg)
In Arp's class "double galaxies, infall and attraction"
See UGC 07860
"Knots resolved with 48-inch. Diffuse counter tail on companion" (Arp)

22. 1964RC1...C...0000d
Re:NGC 4631
= Holm 442a
Probably an end-on front view of a late SB(s). Complex, dark markings.
Partially resolved, asymmetric outer arms.
See also HA, 105, 231, 1937.
Mean velocity of the brightest emission patch 1.3 arcmin following center:
V = +662 km/sec (source B,D,G,J).
Interacting pair with NGC 4627 at 2.5 arcmin.
Photograph:
M.N.R.A.S., 85, 1019, 1925.
Photometry:
Ap. J., 91, 528, 1940.
Izv. Pulkovo, 20, No.156, 87, 1956.
Soviet A.J., 32, 16, 1955.
Spectrum:
P.A.S.P., 69, 302, 1957.
Rotation and Mass:
A.J., 67, 113, 1962.
Ap. J., 137, 363, 1963.
HII Regions:
Zeit. fur Ap., 50, 168, 1960.
Radio Emission;
M.N.R.A.S., 122, 479, 1961.
HI Emission:
Epstein, Harvard Thesis, 1962.

23. 1961Hubbl.B...0000S
Re:NGC 4631
Sc
PH-208-MH
May 15/16, 1950
103aO
30 min
Enlarged 1.0X
NGC 4631 is probably a late Sc. There is no sign of a
nuclear bulge. The entire surface is resolved into stars
and HII regions. There are many dust patches but no
strong dust lane across the spindle as in NGC 4565 or NGC 0891.
The small companion galaxy north of NGC 4631 is NGC 4627,
an E5 or S01 galaxy with indication of globular clusters
surrounding the main body. It is likely that NGC 4627 forms
a dynamical unit with NGC 4631 similar to the M32, NGC 0205,
M31 system. However, no redshift is available for NGC 4627.

24. 1957HPh....53..275d
Re:NGC 4631
SB(s)d or m(sp)
(Plate 48)
The nearly central, brighter part which is not resolved,
(and against which dark clouds are projected) represents
a "front" end-on view of the axis; from it emerge two,
well-resolved, irregular spiral arms spreading out in
opposite directions.
Note the characteristic asymmetry.
Compare with NGC 1313 (Plate 32), And. Dwarf I (Plate 38),
NGC 4244 (Plate 42), and NGC 0055 (Plate 47).

25. 1918PLicO..13....9C
Re:NGC 4631
Vol. VIII, Plate 41. Very bright; it is 12' x 1.2' in p.a. 86^deg^. Numerous
almost stellar condensations, and a very irregular absorption lane extending
throughout most of its length. A bright, irregular mass 1' e. of the center of
figure may be the nucleus. See Abs. Eff. 15 s.n.


Back to NED Home