2008MNRAS.390..408Z


Query : 2008MNRAS.390..408Z

2008MNRAS.390..408Z - Mon. Not. R. Astron. Soc., 390, 408-420 (2008/October-2)

The NGC 672 and 784 galaxy groups: evidence for galaxy formation and growth along a nearby dark matter filament.

ZITRIN A. and BROSCH N.

Abstract (from CDS):

We present U, B, V, R, I, Hα and NUV photometry of 14 galaxies in the very local Universe (within 10 Mpc). Most objects are dwarf irregular galaxies (dIrr) and are probably associated with the NGC 672/IC 1727 and NGC 784 galaxy groups. The galaxies are at low redshift (51 ≤v≤ 610km/s) and most appear projected on the sky as a 6° long linear filament. We show that the galaxy positions along this filament correlate with their radial velocity, hinting to an interpretation as a single kinematic entity. Our CCD photometry indicates that all objects qualify as `dwarf galaxies' with MB≥ -18 mag. We examine the star formation (SF) properties of individual objects in the context of their immediate environment. The current SF rate (SFR) is derived directly from the Hα line flux. An approximate SF history is derived by comparing the multiband photometry with results of galaxy evolution models from (Bruzual & Charlot (2003a,b), assuming short SF bursts separated by long quiescence periods.

Relations between the current SFR and the HI mass or the absolute B magnitude for the galaxies in these groups indicate that these objects behave like normal galaxies. A comparison of the photometric measurements with evolutionary synthesis model predictions indicates that most objects can be understood as containing at least one `old' stellar population (≥1-10 Gyr) and one `young' population (≤30 Myr). For both groups, the recent SF bursts appear to have occurred at similar times, a few to a few tens of Myr ago, arguing for synchronicity in SF in these objects.

In an attempt to evaluate the possible role of galaxy-galaxy interaction, we investigate the trend of the SFR with an object's projected distance from the brightest and most massive galaxies of each group. We do not find a steadily decreasing SF as function of this distance; such a result could be expected if the SF would have been triggered by interactions. We propose that one possible explanation of the nearly synchronous SF in all objects is accretion of cold gas from intergalactic space on to dark matter haloes arranged along a filament threading the void where these dwarf galaxies reside. We point out this galaxy sample as an ideal target to study hierarchical clustering and galaxy formation among very nearby objects.


Abstract Copyright: © 2008 The Authors. Journal compilation © 2008 RAS

Journal keyword(s): star: formation - galaxies: interactions

CDS comments: In Table 1 : NGC 111946 is a misprint for AGC 111946

Simbad objects: 20

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Number of rows : 20
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
#notes
1 LEDA 169957 AG? 01 36 35.920 +23 48 55.81   17.74       ~ 11 0
2 NAME NGC 628 Group GrG 01 36.7 +15 47           ~ 11 0
3 LEDA 5057055 AG? 01 41 08.00 +27 19 20.0           ~ 32 0
4 LEDA 138451 AG? 01 42 17.40 +26 22 00.0   16.6       ~ 44 0
5 LEDA 166062 AG? 01 44 42.3853 +27 17 16.156   17.1       ~ 45 0
6 LEDA 166063 G 01 46 42.2 +26 48 05   18.22       ~ 41 0
7 IC 1727 GiP 01 47 29.890 +27 20 00.06   12.54 11.98 11.77   ~ 201 0
8 NGC 672 GiP 01 47 54.4764771528 +27 25 58.020709728 12.04 11.60 11.09 10.81   ~ 287 0
9 UGC 1281 LSB 01 49 31.71 +32 35 16.2   13.0       ~ 167 0
10 LEDA 166064 AG? 01 55 20.30 +27 57 14.0   16.3       ~ 56 0
11 LEDA 166065 G 02 00 10.2 +28 49 53   17.2       ~ 63 0
12 NGC 784 LSB 02 01 16.932 +28 50 14.13 12.97 12.50 12.07 11.83   ~ 197 0
13 LEDA 1858273 G 02 03 45.1918857624 +29 10 53.169560364           ~ 8 0
14 UGC 1561 AG? 02 04 04.9 +24 12 35   14.7       ~ 37 0
15 NGC 855 GiG 02 14 03.612 +27 52 37.82 14.19 13.56 12.75 12.40   ~ 229 1
16 NAME NGC 925 Group GrG 02 27 16.80 +33 34 44.5           ~ 2 0
17 NAME M 81-82 Group GrG 09 55 +69.1           ~ 717 0
18 NAME Virgo Cluster ClG 12 26 32.1 +12 43 24           ~ 6653 0
19 NAME NGC 672 Group GrG ~ ~           ~ 14 0
20 NAME NGC 784 Group GrG ~ ~           ~ 17 0

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