Large depletion time variation in the interacting galaxy ...Large depletion time variation in the...
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Large depletion time variation in the interacting galaxy NGC 2276 Neven Tomičić 1 , A. Hughes 2 , K. Kreckel 1 , F. Renaud 3 , E. Schinnerer 1 , J. Pety 4 , S. Meidt 1 , T. Saito 1 , M. Querejeta 5 , C. Faesi 1 , S. Garcia-Burillo 6 ABSTRACT: 1) Max Planck Institute for Astronomy, Heidelberg, Germany; 2) Universite de Toulouse, UPS-OMP, 31028 Toulouse, France; 3) Lund Observatory, Sölvegatan 27, Box 43, SE-221 00 Lund, Sweden; 4) Institut de Radioastronomie Millimétrique Grenoble, France; 5) European Southern Observatory, Karl-Schwarzschild Str. 2, 85748 Garching bei München,Germany; 6) Observatorio Astronómico Nacional, Aptdo 1143, 28800 Alcalá de Henares, Spain; [email protected] Background image: credit- Adam Block/Mount Lemmon SkyCenter/University of Arizona, Wikipedia.org References ➢ Gruendl, Vogel, Davis et al. 1993, ApJ, 413L, 81G ➢ Hughes, Pety, Tomicic et al. 2018, in prep. ➢ Leroy, Walter, Sandstrom 2013, AJ, 146, 19L ➢ Rasmussen, Ponman, Mulchaey 2006, MNRAS, 370, 453R ➢ Renaud, Famaey, Kroupa et al. 2016, MNRAS, 463, 3637R ➢ Renaud et al. 2018 in prep ➢ Tomicic, Hughes, Kreckel et al. 2018, in prep. logΣ(SFR) logΣ(M stellar ) DATA: RESULTS: NGC 2276 & TIDAL FORCE: RAM PRESSURE: ● We observe the interacting galaxy NGC 2276 with optical IFU spectrograph (for extinction corrected Hα, and SFR surface density) and with both IRAM mm facilities (for CO and H 2 surface density). ● The global value of the H 2 depletion time t depl (H 2 ) in NGC 2276 is 0.55 Gyr, unusually low compared to 2 Gy (with 0.3 dex scatter) typically observed in nearby main sequence galaxies (Leroy et al. 2013). ● There is a gradual decrease in t depl (H 2 ) by 1 dex across the disk, and an additional 1 dex drop on the western edge. We attribute this decrease to the tidal force (affecting the entire disk) and ram pressure (affecting the western edge) acting on NGC 2276. Σ(SFR) map derived from our extinction corrected Hα map. We derive the Hα map from optical IFU spectra, using PMAS (Calar Alto, Spain). The maps are at 2.7’’ resolution (≈400 pc). Credit- Tomicic et al. 2018 in prep. Σ(M H2 ) map derived from C(J=1-0) emission, observed with the PdBI interferometer and 30m telescope (IRAM). Credit- Hughes et al. 2018 in prep. logΣ(M H2 ) N E Depletion time t depl (H 2 ) map derived from Σ(SFR) and Σ(M H2 ). We focus on a strip, in the NE-SW direction, and show this data on the Kennicutt-Schmidt diagram, below. The Kennicutt-Schmidt diagram with the data from the NE-SW strip, colored by the location in the strip. We added the HERACLES data for nearby galaxies (contours; Leroy et al. 2013) and the global value for NGC 2276 (X symbol). NGC 2276 is an interacting spiral galaxy in the group of NGC 2300. It shows asymmetry in emission of various SFR tracers (Griendl et al. 1993), and has an unusually high global SFR of 5-20 M sol /yr, given its stellar mass. There are various observations indicating a strong tidal force affecting NGC 2276 (Griendl et al. 1993, Rasmussen et al. 2006): 1) truncation in R band images, 2) extended south-east arm in the HI gas, 3) a peculiar Hα velocity field. We observe a truncation and an asymmetry in the stellar mass distribution (right). This is probably caused by tidal forces (Tomicic et al. 2018 in prep). Stellar mass surface density map of NGC 2276 and NGC 2300. We derived the map from WISE images at 3.4 μm and 4.6 μm. Credit- Tomicic et al. 2018 in prep. Strong RAM pressure has been previously observed, acting on the western edge of NGC 2276 (Rasmussen et al. 2006). It is probably due to the high density (10 -27 g/cm 3 ) of the inter-galactic medium. We notice that the Hα corr /FUV corr ratio is high on the western edge, compared to rest of the disk. This indicates younger stellar clusters in the western edge, whose formation is probably triggered by the ram pressure (Tomicic et al. 2018 in prep). N E Source of low depletion time: In NGC 2276, the global value of the depletion time t depl (H 2 ) is 0.55 Gyr. That is low compared to main sequence galaxies that exhibit t depl (H 2 )=2 Gyr (with 0.3 dex scatter), as seen in the HERACLES galaxy survey (Leroy et al. 2013). We notice a gradual drop in the value of t depl (H 2 ) from 5 Gyr to 100 Myr across the disk of NGC 2276, from north-east toward south-west (Figures on the right). An additional drop in t depl (H 2 ) from 100 Myr to 10 Myr is evident on the very western edge of the disk. The enourmous 2 dex decrease in t depl (H 2 ) could be caused by extra-galactic dynamics that affect the ISM and the star formation efficiency (Renaud et al. 2016, Renaud et al. 2018 in prep). Possible forces that decrease the t depl (H 2 ) in NGC 2276: 1) Tidal force – lowers t depl (H 2 ) by ≈1 dex across the entire disk, and caused by the passage of NGC 2276 near NGC 2300. 2) RAM pressure – additionally decrease the t depl (H 2 ) by ≈1 dex on the western edge of NGC 2276, caused by a compression of the gas that enhances its star-formation efficiency even furher.
Transcript of Large depletion time variation in the interacting galaxy ...Large depletion time variation in the...
Large depletion time variation in the interacting galaxy NGC 2276Neven Tomičić1, A. Hughes2, K. Kreckel1, F. Renaud3, E. Schinnerer1, J. Pety4, S. Meidt1, T. Saito1, M. Querejeta5, C. Faesi1, S. Garcia-Burillo6
ABSTRACT:
1) Max Planck Institute for Astronomy, Heidelberg, Germany; 2) Universite de Toulouse, UPS-OMP, 31028 Toulouse, France; 3) Lund Observatory, Sölvegatan 27, Box 43, SE-221 00 Lund, Sweden; 4) Institut de Radioastronomie Millimétrique Grenoble, France; 5) European Southern Observatory, Karl-Schwarzschild Str. 2, 85748 Garching bei München,Germany; 6) Observatorio Astronómico Nacional, Aptdo 1143, 28800 Alcalá de Henares, Spain;
Background image: credit- Adam Block/Mount Lemmon SkyCenter/University of Arizona, Wikipedia.org
References➢Gruendl, Vogel, Davis et al. 1993, ApJ, 413L, 81G➢Hughes, Pety, Tomicic et al. 2018, in prep.➢Leroy, Walter, Sandstrom 2013, AJ, 146, 19L➢Rasmussen, Ponman, Mulchaey 2006, MNRAS, 370, 453R➢Renaud, Famaey, Kroupa et al. 2016, MNRAS, 463, 3637R➢Renaud et al. 2018 in prep➢Tomicic, Hughes, Kreckel et al. 2018, in prep.
logΣ(SFR)
logΣ(Mstellar)
DATA:
RESULTS:
NGC 2276 & TIDAL FORCE:
RAM PRESSURE:
● We observe the interacting galaxy NGC 2276 with optical IFU spectrograph (for extinction corrected Hα, and SFR surface density) and with both IRAM mm facilities (for CO and H2 surface density).
● The global value of the H2 depletion time tdepl(H2) in NGC 2276 is 0.55 Gyr, unusually low compared to 2 Gy (with 0.3 dex scatter) typically observed in nearby main sequence galaxies (Leroy et al. 2013).
● There is a gradual decrease in tdepl(H2) by 1 dex across the disk, and an additional 1 dex drop on the western edge. We attribute this decrease to the tidal force (affecting the entire disk) and ram pressure (affecting the western edge) acting on NGC 2276.
Σ(SFR) map derived from our extinction corrected Hα map. We derive the Hα map from optical IFU spectra, using PMAS (Calar Alto, Spain). The maps are at 2.7’’ resolution (≈400 pc). Credit- Tomicic et al. 2018 in prep.
Σ(MH2) map derived from C(J=1-0) emission, observed with the PdBI interferometer and 30m telescope (IRAM). Credit- Hughes et al. 2018 in prep.
logΣ(MH2)
N
E
Depletion time tdepl(H2) map derived from Σ(SFR) and Σ(MH2). We focus on a strip, in the NE-SW direction, and show this data on the Kennicutt-Schmidt diagram, below.
The Kennicutt-Schmidt diagram with the data from the NE-SW strip, colored by the location in the strip. We added the HERACLES data for nearby galaxies (contours; Leroy et al. 2013) and the global value for NGC 2276 (X symbol).
NGC 2276 is an interacting spiral galaxy in the group of NGC 2300. It shows asymmetry in emission of various SFR tracers (Griendl et al. 1993), and has an unusually high global SFR of 5-20 Msol/yr, given its stellar mass.There are various observations indicating a strong tidal force affecting NGC 2276 (Griendl et al. 1993, Rasmussen et al. 2006): 1) truncation in R band images,2) extended south-east arm in the HI gas,3) a peculiar Hα velocity field. We observe a truncation and an asymmetry in the stellar mass distribution (right). This is probably caused by tidal forces (Tomicic et al. 2018 in prep).
Stellar mass surface density map of NGC 2276 and NGC 2300. We derived the map from WISE images at 3.4 μm and 4.6 μm. Credit- Tomicic et al. 2018 in prep.
Strong RAM pressure has been previously observed, acting on the western edge of NGC 2276 (Rasmussen et al. 2006). It is probably due to the high density (10-27 g/cm3) of the inter-galactic medium.
We notice that the Hαcorr/FUVcorr ratio is high on the western edge, compared to rest of the disk. This indicates younger stellar clusters in the western edge, whose formation is probably triggered by the ram pressure (Tomicic et al. 2018 in prep).
N
E
Source of low depletion time:
In NGC 2276, the global value of the depletion time tdepl(H2) is 0.55 Gyr. That is low compared to main sequence galaxies that exhibit tdepl(H2)=2 Gyr (with 0.3 dex scatter), as seen in the HERACLES galaxy survey (Leroy et al. 2013). We notice a gradual drop in the value of tdepl(H2) from 5 Gyr to 100 Myr across the disk of NGC 2276, from north-east toward south-west (Figures on the right).An additional drop in tdepl(H2) from 100 Myr to 10 Myr is evident on the very western edge of the disk.
The enourmous 2 dex decrease in tdepl(H2) could be caused by extra-galactic dynamics that affect the ISM and the star formation efficiency (Renaud et al. 2016, Renaud et al. 2018 in prep). Possible forces that decrease the tdepl(H2) in NGC 2276:
1) Tidal force – lowers tdepl(H2) by ≈1 dex across the entire disk, and caused by the passage of NGC 2276 near NGC 2300.2) RAM pressure – additionally decrease the tdepl(H2) by ≈1 dex on the western edge of NGC 2276, caused by a compression of the gas that enhances its star-formation efficiency even furher.
