bulk motions of spiral galaxies within z = 0.03

Download Bulk Motions  of Spiral Galaxies within z = 0.03

Post on 17-Mar-2016




0 download

Embed Size (px)


Bulk Motions of Spiral Galaxies within z = 0.03. The 2MASS View of NGC 891. I.D.Karachentsev (SAO RAS ), S.N.Mitronova (SAO RAS), V.E.Karachentseva (Kiev Univ.), Yu.N.Kudrya (Kiev Univ.). - PowerPoint PPT Presentation


  • Bulk Motions of Spiral Galaxieswithin z = 0.03 I.D.Karachentsev (SAO RAS ),S.N.Mitronova (SAO RAS),V.E.Karachentseva (Kiev Univ.),Yu.N.Kudrya (Kiev Univ.)

    The 2MASS View of NGC 891

  • The RFGC (Karachentsev et al. 1999) includes 4236 galaxies with optical angular diameters a>0.6' and apparent axial ratios a/b>7. The RFGC is currently the most uniform all-sky catalog of edge-on late-type spiral galaxies.

    Based on optical TF-relation for 971 galaxies we obtained the dipol parameters:

    V = 300 75 km/s,

    l = 328o 20o, b = +7o 15o.

  • About 3000 galaxies in RFGC have J,H,K photometry in the 2MASS survey. We constructed the 2MASS-TF relations for a sample of 1141 galaxies and determined the bulk motion parameters:V = 226 62 km/s,

    l = 295 16o, b = 2 13o (Kudrya et al. 2003)

  • 2MASS

  • Images of the 2MFGC galaxies

  • The 2MFGC catalog (Mitronova et al. 2004) contains IR photometry and LEDA and NED identifications for 18020 galaxies with axial ratios a/b > 3 in the XSC-2MASS

  • All-sky distribution of 18020 2MFGC galaxies

  • The 2MFGC galaxies with known V and W

  • Magnitude of the bulk velocity (dots) vs depth

  • M = J 25 5 log r, r = V3K / Ho {1 (qo - 1)V3K / 2c}, where qo = -0.55 for standard CDM.

    M = C1 + C2 log W + C3 log Reff + C4 a/b + C5 (IC),Vpec = V3K Ho r {1+(qo - 1) Hor / 2c}.

    We use the set of peculiar velocities to calculate the orthogonal components of the dipole bulk velocity V, _ _ Vpec,i = V ei + Viby minimizing the sum of the squares of the noise peculiar velocity component.

  • Parameters of the 2MFGC dipole bulk velocity:Excluding galaxies with deviations of more than 3(TF) and Vpec > 3000 km/s, we obtain:

    N = 2395 (TF) = 0.45 mag, (V) = 968 km/s,

    V = 199 37 km/s, l = 290o 11o, b = +1o 9o

  • Bulk motion in the Local Group frame:The Sun moves relative to the 3K frame with a velocity of V3K = 369.5 3.0 km/s towardsl = 264.4 0.3o, b = +48.4 0.5o (Kogut et al. 1993), while the LG centroid has a velocity of V3K (LG) = 634 12 km/s relative to the 3K frame in the direction l = 269 3o, b = +28 1o (Karachentsev & Makarov 1996).In the LG frame the bulk motion is: V3K = 372 33 km/sin the direction l = 76 6o, b = -40 6o.Returning to the 3K frame, we obtain: V = 296 km/s, l = 282o, b = +11o.

  • Sky distribution of 2MFGC galaxies in the shells in Galactic coordinates

  • Parameters of the dipole bulk velocity for the 2MFGC galaxies in spherical shells

    Sample, NTFmagVkm/sV km/sldeg. bdeg.FS1, 5090.57 438364 38311 6 4 431S2, 9560.37 738157 45285 16-17 144.4S3, 6450.301003367 85291 11-24 96.4S4, 2850.251187335 143299 22-13 181.8

  • Peculiar velocity distribution for 2395 2MFGC galaxies in Galactic coordinates

  • The peculiar velocity fieldThe peculiar velocity distribution of 2MFGC galaxies is asymmetric: the maximum positive isovelocity is +350 km/s, while the maximum negative isovelocity is only 150 km/s. The Vpec appears doubly connected, with the primary peak being approximately in the zone where the Hydra-Centaurus, Norma, A3627 clusters and the Shapley Concentration of clusters are located. The secondary positive peak with an amplitude of 150 km/s is identified with the Abell cluster A400 (170o, -45o) and A539 (196o, -18o). The region of negative mean peculiar velocities forms three broad shallow troughs with the coordinates of their centers (120o, +40o), (80o, -30o), (200o, +30o). The first two of them lie not far from the well-known Void in Bootes and the Local Void.

  • To estimate the representativeness and quality of the galaxy sample used to determine the dipole parameters, we introduced the concept of goodness, G = (N/100 )1/2/(TF), where N is the number of galaxies in the sample, and TF is their dispersion (in magnitudes) in the TF diagram.

    Goodness for various samples:Sample G V lo bo Reference km/s Spirals in clusters 6.0 75 289 25 Dale et al. (1999)

    SNIa 6.8 206 290 0 Radburn-Smith et al. (2004)

    RFGC 7.4 199 301 2 Kudrya et al. (2003)

    Mark III 8.6 370 305 14 Dekel et al. (1999)

    2MFGC 11.4 199 290 1 This talk

  • The sample of 2MFGC galaxies has the best goodness. The parameters of the 2MFGC dipole are in good agreement with their weighted mean values for all five samples: V = 225 47 km/s, l = 295o 3o, b = +6o 5o. These amplitude and direction of the bulk motion can be currently taken as the standard ones for the bulk flow of galaxies relative to the CMB on a scale of ~100 Mpc. This direction of the dipole is almost opposite to the direction of the rotational velocity of the Sun relative to the Galactic center, V = 220 km/s, l = 90o, b = 0o. For this coincidental reason, the large-scale flow of galaxies had gone unnoticed until the 1980s.

  • ConclusionsThe apex of the bulk flow is located roughly in the same region as the all-sky X-ray selected cluster dipole: l = 292o, b = +3o (Kocevsky & Ebeling 2005).

    If judged by the pattern of decrease in the flow amplitude with linear scale of the Local Volume, then objects (attractors) located farther than 50 Mpc could be responsible for ~60% of the amplitude of the observed bulk motion of 2MFGC galaxies.

  • Thank you!


View more >