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The Closest View of a Dwarf Galaxy: New Evidence on the Nature of the Canis Major over-density
Astrophysics · Submitted 25 Oct 2004
abstract compiled · 2026-09-23 · no language-model review
The authors' main claim These values place the Canis Major object in the category of dwarf galaxy in the the L_{V}--size and M_V - mu_{V} planes for such objects.
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The abstract, sentence by sentence
We present a first deep colour-magnitude diagram of the putative central region (0.5 deg x 0.5 deg) of the Canis Major stellar over-density (l,b)=(240,-8) found by Martin et al. (2004), which has been proposed as the remnant of a dwarf satellite accreted onto the Milky Way on a near-equatorial orbit. We find a narrow (in apparent magnitude) main-sequence, extending 6 magnitudes below the turn-off to our limiting magnitude of B ~ 24.5 mag. This main sequence has very high constrast (>3) with respect to the thin/thick disk/halo background; its narrowness at brighter magnitudes clearly implies the presence of a distinct and possibly still bound stellar system. We derived the line-of-sight size (r_{1/2}) of this system based on the B-band width of the lower main sequence, obtaining 0.94 +/- 0.18 (random) +/- 0.18 (systematic) kpc. That size matches a model prediction for the main body of the parent galaxy of the Monoceros tidal stream. The high density contrast and limited spatial extent in the radial direction are very hard to reconcile with the alternative explanation put forward to explain the Canis Major stellar-overdensity: a flared or warped Galactic disk viewed in projection (Momamy et al. 2004). We also derived a central surface brightness of mu_{V,0}= 23.3 +/- 0.1 mag arcsec^{-2} and an absolute magnitude of M_{V}=-14.5 +/- 0.1 mag. These values place the Canis Major object in the category of dwarf galaxy in the the L_{V}--size and M_V - mu_{V} planes for such objects. However, like the Sagittarius dwarf, it is an outlier in the[Fe/H] -M_V plane in the sense that it is too metal rich for its estimated absolute magnitude. This suggests that the main mechanism driving its recent and current star formation history (possibly tidal stripping) is different to that of isolated dwarfs.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | We present a first deep colour-magnitude diagram of the putative central region (0.5 deg x 0.5 deg) of the Canis Major stellar over-density (l,b)=(240,-8) found by Martin et al. (2004), which has been proposed as the remnant of a dwarf satellite accreted onto the Milky Way on a near-equatorial orbit. | contribution 0.96 | 0.82 | 0.07 | asserted 0.50 |
| s1 | We find a narrow (in apparent magnitude) main-sequence, extending 6 magnitudes below the turn-off to our limiting magnitude of B ~ 24.5 mag. | result 1.00 | 0.97 | 0.05 | asserted 1.00 |
| s2 | This main sequence has very high constrast (>3) with respect to the thin/thick disk/halo background; its narrowness at brighter magnitudes clearly implies the presence of a distinct and possibly still bound stellar system. | result 0.51 | 0.94 | 0.20 | asserted 0.61 |
| s3 | We derived the line-of-sight size (r_{1/2}) of this system based on the B-band width of the lower main sequence, obtaining 0.94 +/- 0.18 (random) +/- 0.18 (systematic) kpc. | result 1.00 | 0.98 | 0.11 | asserted 1.00 |
| s4 | That size matches a model prediction for the main body of the parent galaxy of the Monoceros tidal stream. | interpretation 0.72 | 0.33 | 0.09 | asserted 0.95 |
| s5 | The high density contrast and limited spatial extent in the radial direction are very hard to reconcile with the alternative explanation put forward to explain the Canis Major stellar-overdensity: a flared or warped Galactic disk viewed in projection (Momamy et al. 2004). | interpretation 0.97 | 0.58 | 0.19 | asserted 0.94 |
| s6 | We also derived a central surface brightness of mu_{V,0}= 23.3 +/- 0.1 mag arcsec^{-2} and an absolute magnitude of M_{V}=-14.5 +/- 0.1 mag. | result 1.00 | 0.97 | 0.06 | asserted 1.00 |
| s7 | These values place the Canis Major object in the category of dwarf galaxy in the the L_{V}--size and M_V - mu_{V} planes for such objects. | interpretation 0.79 | 0.83 | 0.30 | asserted 1.00 |
| s8 | However, like the Sagittarius dwarf, it is an outlier in the[Fe/H] -M_V plane in the sense that it is too metal rich for its estimated absolute magnitude. | result 0.66 | 0.59 | 0.10 | asserted 0.92 |
| s9 | This suggests that the main mechanism driving its recent and current star formation history (possibly tidal stripping) is different to that of isolated dwarfs. | interpretation 1.00 | 0.38 | 0.13 | hedged possibility 1.00 |
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The paper
Original abstract
We present a first deep colour-magnitude diagram of the putative central region (0.5 deg x 0.5 deg) of the Canis Major stellar over-density (l,b)=(240,-8) found by Martin et al. (2004), which has been proposed as the remnant of a dwarf satellite accreted onto the Milky Way on a near-equatorial orbit. We find a narrow (in apparent magnitude) main-sequence, extending 6 magnitudes below the turn-off to our limiting magnitude of B ~ 24.5 mag. This main sequence has very high constrast (>3) with respect to the thin/thick disk/halo background; its narrowness at brighter magnitudes clearly implies the presence of a distinct and possibly still bound stellar system. We derived the line-of-sight size (r_{1/2}) of this system based on the B-band width of the lower main sequence, obtaining 0.94 +/- 0.18 (random) +/- 0.18 (systematic) kpc. That size matches a model prediction for the main body of the parent galaxy of the Monoceros tidal stream. The high density contrast and limited spatial extent in the radial direction are very hard to reconcile with the alternative explanation put forward to explain the Canis Major stellar-overdensity: a flared or warped Galactic disk viewed in projection (Momamy et al. 2004). We also derived a central surface brightness of mu_{V,0}= 23.3 +/- 0.1 mag arcsec^{-2} and an absolute magnitude of M_{V}=-14.5 +/- 0.1 mag. These values place the Canis Major object in the category of dwarf galaxy in the the L_{V}--size and M_V - mu_{V} planes for such objects. However, like the Sagittarius dwarf, it is an outlier in the[Fe/H] -M_V plane in the sense that it is too metal rich for its estimated absolute magnitude. This suggests that the main mechanism driving its recent and current star formation history (possibly tidal stripping) is different to that of isolated dwarfs.
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How the literature uses it
2 arXiv papers cite this in 2 sentences
Papers citing it · 1 sentence without a confident label
Cites it as support 1 paper
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The ring at 13 kpc (outer ring) is thought to originate from the tidal disruption of the Canis Major dwarf galaxy, which circles the Galaxy in an almost circular orbit coplanar with the disk [ref] .
The dark connection between the Canis Major dwarf, the Monoceros ring, the gas flaring, the rotation curve and the EGRET excess of diffuse Galactic Gamma Rays · The DMA interpretation of the EGRET excess of diffuse Galactic gamma rays · 0.96
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