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Register a new userTidal destruction in a low mass galaxy environment: the discovery of tidal tails around DDO 44
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We report the discovery of a $>1^circ$ ($sim50$ kpc) long stellar tidal stream emanating from the dwarf galaxy DDO 44, a likely satellite of Local Volume galaxy NGC 2403 located $sim70$ kpc in projection from its companion. NGC 2403 is a roughly Large Magellanic Cloud stellar-mass galaxy 3 Mpc away, residing at the outer limits of the M 81 group. We are mapping a large region around NGC 2403 as part of our MADCASH (Magellanic Analogs Dwarf Companions and Stellar Halos) survey, reaching point source depths (90% completeness) of ($g, i$) = (26.5, 26.2). Density maps of old, metal-poor RGB stars reveal tidal streams extending on two sides of DDO 44, with the streams directed toward NGC 2403. We estimate total luminosities of the original DDO 44 system (dwarf and streams combined) to be $M_{i, rm{tot}} = -13.4$ and $M_{g, rm{tot}} = -12.6$, with $sim25-30%$ of the luminosity in the streams. Analogs of $sim$LMC-mass hosts with massive tidally disrupting satellites are rare in the Illustris simulations, especially at large separations such as that of DDO 44. The few analogs that are present in the models suggest that even low-mass hosts can efficiently quench their massive satellites.
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We report the detection of a pair of degree-long tidal tails associated with the globular cluster Palomar 14, using images obtained at the CFHT. We reveal a power-law departure from a King profile at large distances to the cluster center. The density map constructed with the optimal matched filter technique shows a nearly symmetrical and elongated distribution of stars on both sides of the cluster, forming a S-shape characteristic of mass loss. This evidence may be the telltale signature of tidal stripping in action. This, together with its large Galactocentric distance, imposes strong constraints on its orbit and/or origin: i) it must follow an external orbit confined to the peripheral region of the Galactic halo and/or ii) it formed in a satellite galaxy later accreted by the Milky Way.
We use photometry from the DECam Legacy Survey to detect candidate tidal tails extending ~5 deg on either side of the Palomar 13 globular cluster. The tails are aligned with the proper motion of Palomar 13 and are consistent with its old, metal-poor stellar population. We identify three RR Lyrae stars that are plausibly associated with the tails, in addition to four previously known in the cluster. From these RR Lyrae stars, we find that the mean distance to the cluster and tails is $23.6 pm 0.2$ kpc and estimate the total (initial) luminosity of the cluster to be $L_V=5.1^{+9.7}_{-3.4}times 10^3 L_odot$, consistent with previous claims that its initial luminosity was higher than its current luminosity. Combined with previously-determined proper motion and radial velocity measurements of the cluster, we find that Palomar 13 is on a highly eccentric orbit ($esim 0.8$) with a pericenter of ~9 kpc and an apocenter of ~69 kpc, and a recent pericentric passage of the cluster ~75 Myr ago. We note a prominent linear structure in the interstellar dust map that runs parallel to the candidate tidal features, but conclude that reddening due to dust is unlikely to account for the structure that we observe. If confirmed, the Palomar 13 stellar stream would be one of very few streams with a known progenitor system, making it uniquely powerful for studying the disruption of globular clusters, the formation of the stellar halo, and the distribution of matter within our Galaxy.
We report the discovery of tidal tails around the Galactic globular cluster NGC 7492, based on the Data Release 1 of the Pan-STARRS 1 survey. The tails were detected with a version of the matched filter technique applied to the $(g-r,r)$ and $(g-i,i)$ color-magnitude diagrams. Tidal tails emerging from the cluster extend at least $sim$3.5 degrees in the North-East to South-East direction, equivalent to $sim1.5$ kpc in projected length.
We report the discovery of a giant stellar tidal stream in the halo of NGC 4631, a nearby edge-on spiral galaxy interacting with the spiral NGC 4656, in deep images taken with a 40-cm aperture robotic telescope. The stream has two components: a bridge-like feature extended between NGC 4631 and NGC 4656 (stream_SE) and an overdensity with extended features on the opposite side of the NGC 4631 disk (stream_NW). Together, these features extend more than 85 kpc and display a clear (g-r) colour gradient. The orientation of stream_SE relative to the orientations of NGC 4631 and NGC 4656 is not consistent with an origin from interaction between these two spirals, and is more likely debris from a satellite encounter. The stellar tidal features can be qualitatively reproduced in an N-body model of the tidal disruption of a single, massive dwarf satellite on a moderately eccentric orbit (e=0.6) around NGC 4631 over $sim$ 3.5 Gyr, with a dynamical mass ratio (m1:m2) of ~40. Both modelling and inferences from the morphology of the streams indicate these are not associated with the complex HI tidal features observed between both spirals, which likely originate from a more recent, gas-rich accretion event. The detailed structure of stream_NW suggests it may contain the progenitor of the stream, in agreement with the N-body model. In addition, stream_NW is roughly aligned with two very faint dwarf spheroidal candidates. The system of dwarf galaxies and the tidal stream around NGC 4631 can provide an additional interesting case for exploring the anisotropy distribution of satellite galaxies recently reported in Local Group spiral galaxies by means of future follow-up observations.
We measure the spatial density of F turnoff stars in the Sagittarius dwarf tidal stream, from Sloan Digital Sky Survey (SDSS) data, using statistical photometric parallax. We find a set of continuous, consistent parameters that describe the leading Sgr streams position, direction, and width for 15 stripes in the North Galactic Cap, and 3 stripes in the South Galactic Cap. We produce a catalog of stars that has the density characteristics of the dominant leading Sgr tidal stream that can be compared with simulations. We find that the width of the leading (North) tidal tail is consistent with recent triaxial and axisymmetric halo model simulations. The density along the stream is roughly consistent common disruption models in the North, but possibly not in the South. We explore the possibility that one or more of the dominant Sgr streams has been mis-identified, and that one or more of the `bifurcated pieces is the real Sgr tidal tail, but we do not reach definite conclusions. If two dwarf progenitors are assumed, fits to the planes of the dominant and `bifurcated tidal tails favor an association of the Sgr dwarf spheroidal galaxy with the dominant Southern stream and the `bifurcated stream in the North. In the North Galactic Cap, the best fit Hernquist density profile for the smooth component of the stellar halo is oblate, with a flattening parameter q = 0.53, and a scale length of r_0 = 6.73. The Southern data for both the tidal debris and the smooth component of the stellar halo do not match the model fits to the North, although the stellar halo is still overwhelmingly oblate. Finally, we verify that we can reproduce the parameter fits on the asynchronous Milkyway@home volunteer computing platform.
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